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Class 11 Biology Revision Notes for Neural Control and Coordination of Chapter 21

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• Coordination is the process through which two or more organs interact and complement the function of each other.
• Neural system provides an organized network of point to point connection for quick coordination. The endocrine system provides chemical integration through hormones.
• Neural system of animals is composed of specialized cells called neuron, which can detect, receive and transmit different kinds of stimuli. In hydra neural system is composed of network of neuron. In insects it consists of brain and a number of ganglia. Vertebrates have highly developed neural system.
• Central nervous system (CNS) includes brain and spinal cord. It is the site for information processing and control.

• Peripheral nervous system includes all nerves associated with CNS. There are two types of nerve fibres-

• Afferent fibres- transmit impulses from tissue/organ to CNS.
• Efferent fibres- transmit regulatory impulses from CNS to concerned peripheral organs.
  Somatic neural systems relay impulses from CNS to skeletal muscles. Autonomic neural system transmits impulses from CNS to involuntary system and smooth muscles.

Neuron as Structural and Functional Unit of Neural System
Neuron is made up of three major parts- cell body, dendrite and axon.

• Cell body contains cytoplasm, cell organelles and Nissl’s granules. Short fibres projecting out from cell body is called dendrites. The axon is long fibre having branched structure at the end that terminates into knob like structure called synaptic knob.
• Based on number of axon and dendrites neuron are of three types-
  1. Multipolar– one axon and two or more dendrite found in cerebral cortex.
  2. Bipolar– one axon and one dendrite found in retina of eyes.
  3. Unipolar– cell body with only one axon found in embryonic stage.

• There are two types of axon-
  • Myelinated– fibres are enveloped with Schwann cells to form myelin sheath around the axon. The gap between two myelin sheaths is called nodes of Ranvier. Found in spinal and cranial nerves.
  • Unmyelinated- fibre is enclosed by Schwann cells that do not form myelin sheath around the axon. Found in autonomous and somatic neural system.

Generation and Conduction of Nerve Impulse

• Ion channels are present in neural membrane which is selectively permeable to different ions. When neuron is not conducting impulse (resting), axonal membrane is more permeable to K+ ions and impermeable to Na+ ions.
• Ionic gradient across the resting membrane is maintained by active transport of ions by sodium-potassium pump. This will develop positive charge outside the axonal membrane and negative charge on inner side.

• The electrical potential difference across the resting membrane is called resting potential.
• When stimulus is applied at site A, the membrane becomes permeable to Na+ ions to make rapid influx of Na+ ions to create outer surface negatively charged and inner membrane positively charged that create Action Potential or nerve impulse.
• The nerve impulse from A moves to B in inner surface and B to A on outer surface. This process is repeated several times to transmit the impulse.
• Nerve impulse is transmitted from one neuron to another neuron through synapse.
• There are two types of synapse-

1. Electrical synapse- the membrane of pre and post synaptic neuron is very close to each other and current flow directly from one neuron to another.
2. Chemical synapse- pre and post synaptic neuron is separated by fluid filled space called synaptic cleft. Neurotransmitters are involved in transmission of impulses.

Central Neural System –Brain is the central information processing organ of our body and act as command and control centre. Human brain is protected by skull (cranium) and three layers of cranial meninges- outer dura mater, middle arachnoid and inner pia mater.

Brain can be divided 3 parts- forebrain, midbrain and hindbrain.
Forebrain– consists of cerebrum, thalamus and hypothalamus. Cerebrum is divided into left and right cerebral hemispheres which are covered by cerebral cortex (grey matter). Cerebral cortex contains sensory neuron, motor neuron and association area. Association area controls complex functions like intersensory associations, memory and
communication.
Thalamus– cerebrum wraps around a structure called thalamus. It is a major
coordinating centre for sensory and motor signaling.
Hypothalamus controls the urge for eating, drinking and body temperature. They also release hypothalamic hormones. Limbic system is involved in controlling sexual behavior and expression of emotional reactions.
Midbrain is located between hypothalamus and pons of hindbrain. Dorsal portion consists of four round lobes called corpora quadrigemina. They are involved in relay of impulses back and forth between cerebrum, cerebellum, pons and medulla.
Hind brain consists of pons, medulla oblongata and cerebellum.
Pons consists of fibre tracts that interconnect different regions of the brain.
The medulla contains centres which control respiration, cardiovascular reflexes and gastric secretions.
Cerebellum controls balance and posture.
Reflex action is a spontaneous autonomic mechanical response to a stimulus without the will of the organism. It is controlled by spinal cord. The afferent neuron receives the signal from sensory organs and transmits the impulse to CNS. The efferent neuron carries the impulse from CNS to effector. Ex- knee-jerk reflex. The path followed by reflex action is called reflex arc.

Human Eye – spherical structure consists of three layers, external layer is sclera whose anterior part is called cornea, middle layer choroid and innermost layer is called retina.
Retina contains three layers of cells – inner ganglion cells, middle bipolar cells and outer photoreceptor cells.
There are two types of photoreceptor cells called rods and cones. The daylight (photopic) vision and colour vision are functions of cones. The twilight (scotopic) vision is the function of the rods.
Mechanism of Vision
The light rays of visible wavelength fall on retina through cornea and lens to generate impulses in rods and cones. Photosensitive pigments opsin and retinal get dissociated due to light to change its shape. Change in shape of opsin cause change of permeability to generate action potential that is transmitted to brain via optic nerve.
Human Ears

Divided into three regions: outer ear, middle ear and inner ear.
The middle ear contains three ossicles called malleus, incus and stapes. The fluid
filled inner ear is called the labyrinth, and the coiled portion of the labyrinth is called cochlea.
The organ of corti contains hair cells that act as auditory receptors and is located on the basilar membrane.
Mechanism of Hearing
External ear receives the sound wave and directs them to ear drum. Vibration of ear drum leads to vibration of ear ossicles. The vibration reaches cochlea that generate wave in lymph. The waves generate ripples in basilar membrane and hair cells in them. As a result, nerve impulses are generated in afferent neuron that passes to brain via auditory nerves.

Class 11 Biology Revision Notes for Locomotion and Movement of Chapter 20

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Locomotion is the voluntary movement of an individual from one place to another. Walking, running, climbing, swimming are the examples of locomotion. All locomotion are movement but all movements are not locomotion.
Types of Movement
Cells of the human body show three main types of movements:

• Macrophages and leucocytes in blood exhibit amoeboid movements. Coordinated movement of cilia in trachea to remove dusts particles and passage of ova through fallopian tube is example of Ciliary movements.
• Movement of limbs, jaw, tongue, etc. need muscular movement. Contractile property of muscles is used in movement in higher organism including human beings.

Muscles are specialized tissues of mesodermal origin. They have property like excitability, contractility, extensibility and elasticity.
Based on their location, three types of muscles are identified

Skeletal Muscles	Visceral Muscles	Cardiac Muscles
Associated with skeletal system, alternate light and dark bands (striated), voluntary and locomotory and change in body posture function.	Form inner wall of internal visceral organs, non-striated, involuntary muscle, assists in movement of food through digestive tract and gametes.	Muscles of heart, having branching pattern, alternate light and dark bands, involuntary in action.

• Skeletal Muscle is made up of muscles bundles (fascicles), held together by collagenous connective tissue called fascia.

• Each muscle bundle contains a number of muscle fibres. Each muscle fibre is lined by plasma membrane called sarcolemma enclosing sarcoplasm. Partially arranged myofibrils are present in muscle bundle having alternate light and dark bands due to presence of protein- actin and myosin
• Light bands contain actin and is called I-band (isotropic band) and dark band contains myosin, called A-band (anisotropic band). Both bands are present parallel to each other in longitudinal fashion.
• In centre of each I-band is elastic fibre called ‘Z’ line. In the middle of A-band is thin fibrous ‘M’ line. The portion of myofibrils between two successive ‘Z’ lines is the functional unit of contraction called a sarcomere.
• At resting stage thin filament overlaps the thick filament. The part of thick filament not overlapped is called ‘H’ zone.

Structure of contractile Protein
Each thin filament (actin) is made of two ‘F’ actins helically wounded to each other. Two filaments of another protein, tropomyosin runs close to it. A complex protein
Troponin is distributed at regular intervals on the tropomyosin.

Each myosin filament is made of many monomeric proteins called Meromyosins. Each meromyosin has globular head with short arm and tails. Globular head has ATP binding sites.
Mechanism of muscle contraction

• The mechanism of muscle contraction is explained by sliding mechanism theory in which thin filament slide over thick filament.
• Muscle contraction start with signal sent by CNS via motor neuron. Neural signal release neurotransmitter ( Acetyl choline) to generate action potential in the sarcolemma.
• This causes the release of Ca ++ from sarcoplasmic reticulum.
• Ca ++ activates actin which binds to the myosin head to form a cross bridge.
• These cross bridges pull the actin filaments causing them to slide over the myosin filaments and thereby causing contraction.
• Ca ++ are then returned to sarcoplasmic reticulum which inactivate the actin. Cross bridges are broken and the muscles relax.

Muscles are classified as:
Red fibres (aerobic muscles-) contain myoglobin that has plenty of mitochondria to use large amount of oxygen stored in them.
White fibres-the muscle fibres containing less number of myoglobin are called white fibres.
Skeletal System
Framework of bones and cartilage forms the skeletal system. In human beings, it consists of 206 bones and some cartilages. The two principle division of skeletal system are:

1. Axial Skeleton (80 bones)- includes skull, vertebral column, sternum and ribs constitute axial system.

• The skull (22 bones) is composed of cranial and facial bones. Cranial (8 bones) forms protective covering for brain (cranium). The facial region consists of 14 skeletal systems that form front part of skull. Hyoid bone (U-shaped) forms the base of buccal cavity.
• The middle ear bone (Malleus, Incus and Stapes) collectively called Ear Ossicles. Skull joins with vertebral column with two occipital condyle.
• Vertebral column consists of 26 serially arranged vertebrae. First vertebra is atlas that combines with occipital condyle. Other includes Cervical-7, thoracic -12, lumbar -5, sacral – 1 coccoygeal -1.
• 12 pairs of ribs connected dorsally to vertebral column and ventrally to sternum. 11th and 12th rib bones are not connected with sternum and are called floating ribs.

Appendicular Skeleton- includes bones of limbs and girdles. Each limb contains 30 bones.
 

Upper Arm	Lower Limb
Humerus, radius and ulna, 8-carpels, 5-metacarpels, 14-phalanges,	Femur, tibia and fibula, 7-tarsals, 5-metatarsals, 14-phalanges, cup shaped patella cover the knee.

Pectoral and Pelvic girdle bones help in the articulation of the upper and the lower limbs
respectively with the axial skeleton.
Pectoral girdle consists of a clavicle and a scapula.
Pelvic girdle consists of two coxal bones. Each coxal bone is formed by the fusion of three bones – ilium, ischium and pubis.

1. Fibrous joints– do not allow any movements. Present in flat skull bones to form cranium.
2. Cartilaginous joints– bones are held together with the help of cartilage present in vertebrae. Permits limited movements.
3. Synovial joints– fluid filled synovial cavity, provide considerable movements. Ball and socket joint, hinge joints, pivot joints, gliding joints etc.

Disorders of Muscular and Skeletal System

• Myasthenia gravis- auto immune disorder affecting neuromuscular junction causing fatigue, weakening and paralysis of skeletal system.
• Muscular Dystrophy- degeneration of skeletal muscles due to genetic disorder.
• Osteoporosis – decreased bone mass in old age leading to chance of fracture due to decreased estrogen.
• Arthritis- inflammation of joints.
• Gout- inflammation of joints due to accumulation of uric acid crystals.
• Tetany- Rapid spasms in muscle due to low Ca ++ in body fluid

Class 11 Biology Revision Notes for Excretory Products and their Elimination of Chapter 19

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• Elimination of metabolic waste products from the animal body to regulate the composition of body fluids and tissues is called excretion. These waste products include ammonia, uric acid, urea, carbon dioxide and ions like Na+Na+, K+K+, Cl^– and phosphates and sulphate.
• Ammonia is the most toxic and uric acid is the least toxic. The process of removing ammonia is called ammonotelism and organisms that excrete ammonia are called ammonotelic (bony fishes, aquatic amphibians and insects).
• The organism that release urea as nitrogenous wastes are called ureotelic (mammals, terrestrial amphibians). The organism that excretes uric acids is called uricotelic (reptiles, birds and land snails).

Animals	Excretory organs
Flat worms, some annelids and cephalochordates.	Protonephridia or flame cells.
Earthworms and annelids	Nephridia
Insects including cockroaches	Malpighian tubules
Mammals	Kidney

Human Excretory System
Human excretory system consists of:

1. A pair of kidneys
2. A pair of ureters
3. A urinary bladder
4. A urethra

• Kidneys are reddish brown bean shaped structure situated between last thoracic and lumber vertebra. Each kidney has a notch on its inner side called hilum through which ureter, blood vessels and nerves enter.

• Inside the hilum has broad funnel shaped space called renal pelvis with projection called calyces.

• Inside the kidney are two zone- outer cortex and inner medulla. Medulla is divided into medullary pyramids projecting into calyx.
• Cortex extends between medullary pyramids as renal column called Columns of Bertini.

• The functional unit of kidney is nephron. Each kidney contains about one million nephrons.
• Each nephron has two parts- the glomerulus and renal tubules. Glomerulus is the tuft of capillaries formed by afferent arteriole. Blood from glomerulus is carried away by efferent arteriole.
• Renal tubules starts with Bowman’s capsule continue with tubular parts divided into Proximal Convoluted tubules, Henle’s loop and Distal Convoluted tubule.

• The malpighian tubules, PCT and DCT of nephron are situated in cortical region where as loops of Henle’s into medulla.

Juxta medullary Nephrons	Cortical Nephrons
a. Loop of Henle’s is short and extend only a little into medulla.	a. Loop of Henle’s are very long and extend deep into medulla.
b. The glomeruli lie close to the inner margin of the cortex.	b. The glomeruli lie in the outer cortex.

Urine formation

• Glomerular capillaries blood pressure cause filtration of blood through 3 layers (endothelium of glomerular blood vessels, epithelium of Bowman’s capsule and basement layer between two membranes as ultra-filtration.
• The amount of filtrate formed by kidneys per minute is called glomerular filtration rate (GFR) which is 125 ml/minute.
• Glomerular Filtration rate is controlled by Juxta glomerular apparatus (JGA).
• 99% of filtrate has to be reabsorbed by renal tubules called reabsorption.

Function of Tubules

1. Proximal Convoluted Tubules (PCT) – all the important nutrients, 70-80% electrolytes and water are reabsorbed.
2. Henle’s Loop– maintains high osmolarity of medullary interstitial fluid.
3. Distal Convoluted Tubules (DCT) – conditional reabsorption of Na+ and water. Maintains pH and sodium- potassium balance.
4. Collecting Duct– large amount of water is reabsorbed to produce concentrated urine.

Mechanism of concentration of urine– The flow of filtrate in two limbs of Henle’s loop is in opposite direction to form counter current. The flow of blood in two limbs of vasa recta increase the osmolarity towards the inner medullary interstitium in the inner medulla.

• The transport of substance facilitated by special arrangement of Henle’s loop and vasa recta is called counter current mechanism.

Regulation of kidney function–

• Functioning of kidney is monitored by hormonal feedback mechanism of hypothalamus and JGA. Change in blood volume, body fluid and ion concentration activates the osmoreceptors in the body that stimulate the hypothalamus to release ADH or vasopressin hormones. The ADH facilitates water absorption in tubules.
• Decrease in glomerular blood pressure activate JG cells to release renin which converts angiotensinogen to angiotensin I and II that increase the glomerular blood pressure and release of aldosterone that increase absorption of Na+ ions and water.

Micturition – The process of expulsion of urine from the urinary bladder is called micturition. The neural mechanism that causes it is called micturition reflex. Urine formed in nephron is stored in urinary bladder till a voluntary signal is given by CNS. This initiates the contraction of smooth muscles of the bladder and simultaneous relaxation of the urethral sphincter causing the release of urine.

• Lungs, liver and skin also play important role in process of excretion. Lungs remove CO2CO2 and water, liver eliminates bile containing substances like bilirubin, biliverdin. Sweat glands remove NaCl, small amount of urea and lactic acid. Sebaceous glands excrete sterol, hydrocarbons and waxes.

Disorders of Excretory System

• Uremia– there is high concentration of non-protein nitrogen (urea, uric acid, creatinine). Urea can be removed by hemodialysis.
• Renal failure– also known as kidney failure where glomerular filtration is ceased and both kidney stops working. Kidney transplant is the ultimate method in correction of acute kidney failure.
• Renal Calculi– formation of stone or insoluble mass of crystallized salts formed within the kidney.
• Glomerulonephritis (Bright’s Disease)-inflammation of glomeruli of kidney due to entry of protein or red blood corpuscles in to filtrate due to injury.

Class 11 Biology Revision Notes for Body Fluids and Circulation of Chapter 18

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Body fluids are the medium of transport of nutrients, oxygen and other important substances in the body.

Blood is the most commonly used body fluid in most of the higher organisms. Lymph also transports certain substances like protein and fats.
Blood
Blood is a fluid connective tissue composed of a fluid matrix, plasma and the blood corpuscles. It forms about 30-35% of the extracellular fluid. It is slightly alkaline fluid having pH7.4.

• Plasma is straw coloured viscous fluid that constitutes 55% of blood volume. It consists of 90-92% water, 6-8% protein (fibrinogens, albumins and globulins), glucose, amino acids and small amount of minerals like Na+, Ca++, Cl^– etc.
• Erythrocytes, leucocytes and platelets are collectively called formed elements.
• Erythrocytes are most abundant cells in human body. Total blood count of RBCs is 5-5.5 million, which is slightly less in females due to menstruation. It is formed in bone marrow. Nucleus is absent in mammalian RBCs having biconcave shape.
• Every 100 ml of blood contain 12-16 gm. of haemoglobin. They have life span of 120 days. They are destroyed in spleen( graveyard of RBCs)
• Leucocytes or WBCs are colourless due to absence of haemoglobin. 6000-8000 of WBCs are present in each ml. of blood.

• Neutrophils are most abundant and basophils are least abundant WBCs. Monocytes and neutrophils are phagocytic cells which destroy foreign organisms.

• Basophils secrete histamine, serotonin and heparin that are involved in inflammatory reactions.
• Eosinophils resist infection and allergic reactions. B and T lymphocytes are responsible for immune response of the body.

Thrombocytes or platelets are cell fragments produced from megakaryocytes in bone marrow. 150000-350000 platelets are present in each ml of blood. Platelets are involved in clotting or coagulation of blood in case of injuries.
Blood Groups – blood of human beings differ in certain aspects although it appear same in all individuals. Two main types of grouping are ABO and Rh.
ABO grouping is based on presence or absence of two surface antigens RBC, antigen A and antigen B. The plasma of an individual also contains two antibodies produced in response of antigens.

• During blood transfusion, blood of donor has to be matched with blood of recipients to avoid clumping of RBCs.
• Group ‘O’ blood can be donated to any individual with any blood group, so it is called universal donor.
• Person with ‘AB’ blood group can receive blood from any person of any group, so it is called universal recipient.

Rh grouping – Rh antigen (similar to Rhesus monkey) are observed on surface of RBCs of majority of individuals (about 80%). Such people are called Rh positive (Rh+Rh+) and those in whom this antigen is absent are called Rh negative (Rh−Rh−).

• Erythroblastosis foetalis– if father blood is Rh+ and mother blood is Rh−Rh−, the foetus blood is Rh+. During the delivery of first child there is a possibility of exposure of mother blood with foetus blood to develop antibodies in mother blood. In subsequent pregnancy the mother’s blood can leak into foetus blood and destroy the foetus RBC. This case is called erythroblastosis foetalis.

Coagulation of blood (Blood Clotting)
When an injury is caused to a blood vessel bleeding starts which is stopped by a process called blood clotting. An injury or trauma stimulates the platelets in the blood to release certain factors that activate the mechanism of coagulation. Calcium play important role in blood clotting.
Lymph
During flow of blood through capillaries, some water soluble substances move out in the space between cells of tissues. This fluid released out is called interstitial fluid or tissue fluid. It is similar to the blood but has fewer blood proteins, less calcium and phosphorus and high glucose concentration.

• It is a colourless fluid containing specialized lymphocytes that provide immune response to body.
• Main function of lymph is to provide immunity, carry proteins and fats molecules and transport oxygen, food materials, hormones etc.

Circulatory Pathways

• All vertebrates have a muscular chambered heart.

Fish – 2 chambered heart
Amphibian and Reptiles (except crocodile) – 3 chambered heart.
Crocodile, Birds and Mammals – 4 chambered heart.
Human Circulatory System – consists of 4 chambered muscular heart, closed branching blood vessels and circulatory fluid blood.
Heart is the mesodermally derived muscular organ, present in thoracic cavity between the two lungs protected by double membrane of pericardium.

• The upper two chamber is called atria and lower two chambers are called ventricles. Interatrial septum separate the right and left atrium and thick walled inter ventricle septum separate the ventricles.
• The opening between right atrium and right ventricle is guarded by a three muscular flaps called tricuspid valve. Bicuspid or mitral valve guards the left atrium and ventricle.
• The opening of right and left ventricle to pulmonary artery and aorta respectively is controlled by semilunar valve.
• The nodal tissue present on upper right corner of right atrium is called SAN (sino-atrial node) and those on lower left corner of right atrium is called AVN ( atrio-ventricular node).
• The purkinje fibres along with right and left bundles form the bundle of HIS. The nodal musculature has ability to generate action potential.
• SAN generate maximum number of action potential and is responsible for rhythmic contraction of heart. Therefore it is called pace maker.

Cardiac Cycle

• To begin with, all four chambers are in relaxed state called joint diastole. As the bicuspid and tricuspid valves are open, blood from pulmonary vein and vena cava flows to left and right ventricle respectively. Semilunar valves are closed at this stage.
• SA node generates action potential that contracts both atria (atrial systole). The action potential passes to AV node and bundle of HIS transmit it to ventricular musculature to cause ventricular systole. At the same time atria undergoes relaxation diastole to close the bicuspid and tricuspid valve.
• Semilunar valves open into circulatory system that relax the ventricle and close the valves to prevent back flow of blood.
• As the pressure inside ventricle decreases the bicuspid and tricuspid valve open to repeat the process or cardiac cycle.
• During each cardiac cycle two sounds are produced. The first sound (lub) is due to closure of bicuspid and tricuspid valve and 2nd heart sound (dub) is due to closure of semilunar valve.

ECG (Electrocardiograph) is a graphical representation of electrical activity of heart during cardiac cycle. The electrocardiograph machine is used to obtain electrocardiogram. The patient is connected to three electrical leads to wrists and left ankle.

• The P-wave represents the electrical excitation of atria (depolarisation) which leads to contraction of atria.
• The QRS-wave represents the depolarisation of ventricles, which initiates the ventricular contraction.
• The T-wave represents the return of ventricle from exited to normal state (repolarization). The end of T-wave marks the end of systole. Counting the number of QRS complex in given period of time determine the heartbeat rate.

Double Circulation
Flow of same blood twice through the heart once in oxygenated form and other in deoxygenated form is called double circulation. It includes systematic and pulmonary circulation.
Systematic circulation includes flow of oxygenated blood from the left ventricle to all parts of body and deoxygenated blood from various body parts to the right atrium. All systematic circulation starts form aorta and ends at superior vena cava, inferior vena cava or coronary sinus to right atrium.
The systematic circulation provides oxygen, nutrients and other substances to the tissues and take CO2 and other harmful substances away for removal.

Pulmonary Circulation
The flow of deoxygenated blood from the right ventricle to the lungs and the return of oxygenated blood from the lung to the left atrium is called pulmonary circulation.
Two pulmonary veins from each lung transport the oxygenated blood to the left atrium.
Double circulation prevents the mixing of oxygenated and deoxygenated blood.
Regulation of Cardiac Activity

• Normal activities of heart are regulated by nodal tissue (SA and AV node), so the heart is myogenic.
• A special neural centre in medulla oblongata moderates the cardiac function by ANS. Sympathetic nerve can increase the rate of heart beat and parasympathetic nerve of ANS decrease the rate of heart beat.
• Adrenal medullary hormone also increases the cardiac output.

Disorder of Circulatory System

1. Hypertension (high blood pressure) – Blood pressure higher than (120/80) . 120 mm Hg is the systolic that is pumping pressure and 80 mm Hg is the diastole, resting pressure. It leads to heart disease and affect vital organs like brain and kidney.
2. Coronary Artery Disease (CAD)- commonly called atherosclerosis that affects the blood vessels that supply blood to heart muscles due to deposition of fat, calcium, cholesterol that makes the arteries lumen narrower.
3. Angina- also called angina pectoris, acute chest pain due to less supply of oxygen to heart muscles. It may occur in elderly male and female. It occurs due to restricted blood flow.
4. Heart failure– heart does not pump enough blood to meet the requirement of body. It is also known as congestive heart failure because congestion of lung is one of its causes. Heart failure is different from heart attack ( heart muscle is damaged by inadequate blood supply) and cardiac arrest ( when heart stops beating).
5. Coronary Thrombosis- formation of clot in the coronary artery is coronary thrombosis. It occurs most frequently in the left anterior descending coronary artery.

Class 11 Biology Revision Notes for Breathing and Exchange of Gases of Chapter 17

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The process of exchange of O₂ from the atmosphere with CO₂ produced by the cell is called breathing. It occurs in two stages of inspiration and expiration. During inspiration air enters the lungs from atmosphere and during expiration air leaves the lungs.

Breathing	Respiration
a. It is simply an intake of fresh air and removal of foul air.  b. It is a physical process. c. No energy is released. d. It is an extracellular process.	a. It is the oxidation of food to form carbon dioxide, water and energy.  b. It is a biochemical process. c. Energy is released in form of ATP. d. It is an intracellular process.

Respiratory Organs – Mechanism of breathing varies in different organism according to their body structure and habitat.

Respiratory Organs	Organisms
Entire Body surface	Sponges, coelenterate, flatworms.
Skin	Earthworm.
Tracheal system	Insects
Gills	Pisces, aquatic arthropods.
Lungs	Amphibians, mammals.

Human Respiratory System

• Human respiratory system consists of a pair of nostrils, pharynx, larynx, bronchi and bronchioles that finally terminates into alveoli.
• Nasal chamber open into pharynx that leads to larynx. Larynx contains voice box (sound box) that help in sound production.
• The trachea, primary, secondary and tertiary bronchi and initial bronchioles are supported by incomplete cartilaginous rings to prevent collapsing in absence of air.
• Each bronchiole terminates into an irregular walled, vascularized bag like structure called alveoli.

• The branching network of bronchi, bronchioles and alveoli collectively form the lungs.
• Two lungs are covered with double layered pleura having pleural fluid between them to reduce the friction on lung surface.

• Conducting parts include nostrils, pharynx, larynx and trachea. Main functions include-

1. Transport of atmospheric air to alveoli.
2. Removing foreign particles from air, humidifying it and bringing it to body temperature.

• The exchange parts are alveoli. It is the site of actual diffusion of O2O2 and CO2O2 between blood and atmospheric air.

Steps of Respiration

1. Breathing in which Oxygen rich atmospheric air is diffused in and CO2O2 rich alveolar air is diffused out.
2. Diffusion of gases across alveolar membrane.
3. Transport of gases by blood.
4. Diffusion of O2O2 and CO2O2 between blood and tissues.
5. Utilization of O2O2 by cells to obtain energy and release of CO2O2 (cellular respiration).

Mechanism of Breathing

• Breathing involves inspiration and expiration. During inspiration atmospheric air is drawn in and during expiration, alveolar air is released out.
• Movement of air in and out takes place due to difference in pressure gradient.
• Inspiration occurs when pressure inside the lung is less and expiration occurs when pressure is more in lungs than outside.
• The diaphragm and external and internal intercostal muscles between the ribs help in developing pressure gradient due to change in volume.

• The contraction of intercostal muscles lifts the ribs and sternum causing an increase in volume of thoracic cavity that results in decrease in pressure than the atmospheric pressure. This causes inspiration.
• Relaxation of the diaphragm and intercostal muscles reduce the thoracic volume and increase the pressure causing expiration.
• The volume of air involved in breathing movements is estimated by using spirometer for clinical assessment of pulmonary functions.

Respiratory Volume and Capacities
Tidal volume (TV) – volume of air inspired or expired during a normal respiration. It is about 500mL in healthy man.
Inspiratory Reserve Volume (IRV) – additional volume of air a person can inspire by forceful inspiration. It is about 2500 mL to 3000mL.
Expiatory Reserve Volume (ERV) – additional volume of air a person can expire by forceful expiration. It is about 1000 mL to 1100mL.
Residual Volume (RV) – volume of air remaining in lungs even after a forcible expiration. It is about 1100mL to 1200mL.
Inspiratory Capacity (IC) – TV + IRV
Expiratory Capacity (EC) – TV + ERV
Functional Residual Capacity (FRC) – ERV + RV
Vital Capacity (VC) – maximum volume of air a person can breathe in after a forceful expiration. ERV+ TV+ IRV
Total Lung Capacity (TLC) – total volume of air accommodated in lung at the end of forced inspiration. RV+ ERV+ TV+ IRV or Vital capacity + Residual Volume.

Exchange of Gases

• Exchange of gases takes place at two sites

1. Alveoli to blood
2. Between blood and tissues.

• Exchanges of gases occur by simple diffusion due to pressure/ concentration gradient, solubility of the gases and thickness of membrane.
• Pressure contributed by individual gas in a mixture of gas is called partial pressure represented by pCO2O2 and pO2O2 .
• Partial pressure of Oxygen and carbon dioxide at different part involved in diffusion varies from one part to another and moves from higher partial pressure to lower partial pressure.
• Solubility of CO2O2 is 20-25 times more than solubility of O2O2 , so CO2O2 diffuse much faster through membrane.
• Diffusion membrane is three layered thick, that is alveolar squamous epithelium, endothelium of alveolar capillaries and basement substance between them.

Transport of Gases

• Blood is the medium of transport for CO2O2 and O2O2 . Most of oxygen (97%) is transported through RBC and remaining 3% by blood plasma.
• 20-25% of CO2O2 is transported by RBC, 70% as bicarbonate and rest 7% in dissolved state by blood plasma.

Transport of Oxygen

• Haemoglobin in RBC combines with O2O2 to form Oxyhaemoglobin. Each haemoglobin combine with four oxygen molecules.
• Binding of O2O2 is related with partial pressure of O2O2 and CO2CO2, hydrogen ion concentration and temperature.
• Percentage saturation of haemoglobin and partial pressure of oxygen forms sigmoid curve (oxygen dissociation curve).
• In the alveoli, pO2O2 is more and pCO2O2 is less, less H+ ions concentration and lower temperature favour the binding of O2O2 with hemoglobin. Where opposite condition in tissues favour the dissociation of Oxyhaemoglobin.

Transport of Carbon dioxide

• Carbon dioxide is transported by haemoglobin as carbamino-haemoglobin. In tissues pCO2O2 is high and pO2O2 is less that favour the binding of carbon dioxide with haemoglobin. Opposite condition help in dissociation of carbamino- haemoglobin in alveoli.
• Enzyme carbonic anhydrase help in formation of carbonate ions to transport carbon dioxide.

Regulation of Respiration

• Human beings have ability to maintain and moderate the rate of respiration to fulfill the demand of body tissues by neural system.
• Respiratory rhythm centre is located in medulla region of hind brain. Pneumotaxic centre in pons moderate the function of respiratory rhythm centre.
• Chemo-sensitive area near rhythm centre is highly sensitive to CO2O2 and H+ ions that ultimately control the respiratory rate. Oxygen do not play major role in controlling rate of respiration.

Functions of Respiration–

1. Energy production
2. Maintenance of acid-base balance.
3. Maintenance of temperature
4. Return of blood and lymph.

Mountain Sickness is the condition characterised by the ill effect of hypoxia (shortage of oxygen) in the tissues at high altitude commonly to person going to high altitude for the first time.
Symptoms-

• Loss of appetite, nausea, and vomiting occurs due to expansion of gases in digestive system.
• Breathlessness occurs because of pulmonary oedema.
• Headache, depression, disorientation, lack of sleep, weakness and fatigue.

Disorder of Respiratory System

1. Asthma– it is due to allergic reaction to foreign particles that affect the respiratory tract. The symptoms include coughing, wheezing and difficulty in breathing. This is due to excess of mucus in wall of respiratory tract.
2. Emphysema– is the inflation or abnormal distension of the bronchioles or alveolar sacs of lungs. This occurs due to destroying of septa between alveoli because of smoking and inhalation of other smokes. The exhalation becomes difficult and lung remains inflated.
3. Occupational Respiratory Disorders– occurs due to occupation of individual. This is caused by inhalation of gas, fumes or dust present in surrounding of work place. This includes Silicosis, Asbestoses due to exposer of silica and asbestos. The symptom includes proliferation of fibrous connective tissue of upper part of lung causing inflammation.
4. Pneumonia– it is acute infection or inflammation of the alveoli of the lungs due to bacterium streptococcus pneumoniae. Alveoli become acutely inflamed and most of air space of the alveoli is filled with fluid and dead white blood corpuscles limiting gaseous exchange.

Class 11 Biology Revision Notes for DIGESTION AND ABSORPTION of Chapter 16

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The process of conversion of complex food into simpler absorbable form is called digestion and is carried out by digestive system by mechanical and biochemical methods.
Digestive System- Human digestive system consists of alimentary canal and associated glands.

• Alimentary canal begin with anterior opening mouth and opens out posteriorly through anus. It comprises of following parts:-

1. Mouth- leads to oral cavity or buccal cavity which contains teeth and tongue.
   Upper surface of tongue has small projections called papillae, some of which contain taste buds.
   Each teeth is embedded in socket of jaw bone (thecodont). Milk teeth is replaced by permanent or adult teeth, this type of dentition is called diphyodont. Four different types of teeth (Heterodont) are incisors (I), canine (C), premolar (PM) and molar (M).Dental formula: Each half of the upper and lower jaw has following number of teeth- 2123212321232123
2. Pharynx – oral cavity opens into pharynx which acts as common passage for food and air. Cartilaginous flap called epiglottis prevents the entry of food into wind pipe (glottis) during swallowing.
3. Stomach- Oesophagus leads to stomach. The opening of stomach is guarded by a sphincter (gastro-oesophageal). Stomach is divided into three parts- cardiac, fundic and pyloric.
4. Small intestine- is the longest part of alimentary canal divided into duodenum, jejunum and ileum. Pyloric sphincter is present between stomach and duodenum.
5. Large intestine- ileum opens into large intestine, which is divided into caecum, colon and rectum. Caecum is a blind sac which host microbes. Vermiform appendix arises from caecum. Rectum opens through anus.

Histology of Alimentary canal-
The wall of alimentary canal from Oesophagus to rectum consists of four layers.

1. Serosa– it is the outermost layer made up of squamous epithelium and areolar connective tissue.
2. Muscularis– it is composed of outer longitudinal and inner circular muscle fibres. Muscles fibres are smooth and have network of nerve cells.
3. Submucosa– it consists of loose connective tissue richly supplied with blood and lymphatic vessels. Meissner’s plexus is present between the muscular coat and mucosa that controls the secretion of intestinal juice.
4. Mucosa– is innermost layer lining the lumen of the alimentary canal. It has irregular folding in stomach called rugae and villi in small intestine. Mucosa forms glands in the stomach (gastric glands) and crypts in between the bases of villi in the intestine (crypts of Lieberkuhn).
   

Salivary Glands- secrete saliva in oral cavity. In human beings salivary glands are three pairs- parotid, sublingual, and submandibular.
Liver- it is the largest gland in human body lies in upper right side of the abdominal cavity just below the diaphragm. Hepatic lobules, covered by Glisson’s capsule, are structural and functional unit of liver made up of hepatic cells. The secretion is stored and concentrated in gall bladder. Bile duct and pancreatic duct open together in duodenum by common duct guarded by sphincter of Oddi.

Pancreas- It is soft lobulated greyish pink gland which weighs about 60 gm., consists of exocrine and endocrine portion. The exocrine portion secretes alkaline pancreatic juice and endocrine secretes hormones insulin and glucagon.
Digestion of food
Carbohydrates, fats, proteins and nucleic acids occur in food in the form of large and complex insoluble macromolecules (polymers). These macromolecules are converted into small monomers by the action of enzyme.

• In buccal cavity, teeth and tongue help in mastication and mixing of food. Mucus in saliva mix with masticated food to form bolus.
• Bolus is passed to pharynx and Oesophagus by swallowing or deglutition.
• Chemical digestion of food starts in oral cavity by the action of enzyme salivary amylase and lysozyme.
  Lysozyme acts as antibacterial agent in mouth to prevent infection.
  Salivary amylase breaksdown starch into maltose
• Mucosa of stomach have gastric glands having three types of cells- mucus neck cells that secrete mucus, peptic or chief cells that secretes proenzyme pepsinogen and pariental or oxyntic cells that secretes HCl.
• Food mixes with gastric juice due to churning action of muscular wall to form chyme. HCl activates the pepsinogen to pepsin to digest protein into peptones  and proteoses
• Mucus and bicarbonates present in gastric juice play important role in lubrication and protecting inner wall of stomach from the action of HCl. Renin is a proteolytic enzyme found in gastric juice of infants to digest milk protein.
• The Bile, pancreatic juice and intestinal juice are released in small intestine. Pancreatic juice contain inactive trypsinogen, chymotrypsinogen, procarboxypeptidases, amylases, lipases and nucleases.
• Trypsinogen is activated by enzyme enterokinase in to trypsin, which further activates the other enzyme of intestinal juice.
• Bile contains bile pigments (bilirubin and bil-verdin), bile salts, cholesterol and phospholipids which help in emulsification of fats.
• Secretion of brush border cells of mucosa and goblet cells contain enzyme succus entericus, containing variety of enzymes to complete the process of digestion.

Function of large intestine

1. Absorption of water, minerals and certain drugs.
2. Secretion of mucus for adhering of the undigested food and lubricating it for easy passage.

Absorption of Digested Food
Absorption is the process by which nutrients pass from the alimentary canal into the blood and lymph through its mucous membrane.

• Amino acids, monosaccharide, fatty acids, glycerol, salts, vitamins and water are to be absorbed. About 90% of absorption occurs in small intestine and rest 10% in stomach, mouth and large intestine.
• The passage of different absorbent depends upon concentration gradient for some substances like glucose and amino acids and electrolytes.

Absorption in different part of alimentary canal-

Mouth	Certain drugs coming in contact with the mucosa of mouth and lower side of tongue are absorbed into the blood capillaries lining them.
Stomach	Absorption of water, simple sugar and alcohol takes place.
Small intestine	Glucose, fructose, fatty acids, glycerol and amino acids are absorbed through the mucosa into the blood stream and lymph.
Large intestine	Absorption of water, some minerals and drug takes place.

Disorder of Digestive System
The inflammation of intestinal tract due to bacterial infection, fungal infection and parasitic infection caused by tapeworm, round worm, threadworm and pin worms.

1. Jaundice– it is a disease of liver. In jaundice the skin and the eyes turn yellow due to large quantities of bilirubin pigments in the extra cellular fluid.
2. Vomiting – it is the ejection of stomach content through the mouth. This reflex action is controlled by the vomit Centre in the medulla.
3. Diarrhoea- frequent defection of liquid faeces is known as Diarrhoea. It reduces the absorption of food.
4. Constipation– in constipation the faeces are retained within the rectum as the bowel movements occur irregularly.
5. Indigestion– incomplete digestion usually accompanied by one or more of the following symptoms- pain, nausea, vomiting, heartburn, acid regurgitation, accumulation of gas and escape of gas from the stomach.

Class 11 Biology Revision Notes for Plant Growth and Development of Chapter 15

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• Root, stem, leaves, flowers, fruits and seeds arise in orderly manner in plants. The sequence of growth is as follows-
• Plants complete their vegetative phase to move into reproductive phase in which flower and fruits are formed for continuation of life cycle of plant.
• Development is the sum of two processes growth and differentiation. Intrinsic and extrinsic factors control the process of growth and development in plants.

• Growth is a permanent or irreversible increase in dry weight, size, mass or volume of cell, organ or organism. It is internal or intrinsic in living beings.
• In plants growth is accomplished by cell division, increase in cell number and cell enlargement. So, growth is a quantitative phenomenon which can be measured in relation to time.
• Plant growth is generally indeterminate due to capacity of unlimited growth throughout the life. Meristem tissues are present at the certain locality of plant body.
• The plant growth in which new cells are always being added to plant body due to meristem is called open form of growth.
• Root apical meristem and shoot apical meristem are responsible for primary growth and elongation of plant body along the axis.
• Intercalary meristem located at nodes produce buds and new branches in plants.

• Secondary growth in plants is the function of lateral meristem that is vascular cambium and cork cambium.

Growth is measurable

• At cellular level, growth is the increase in amount of protoplasm. It is difficult to measure the increase in amount of protoplasm but increase in cell, cell number and cell size can be measured.
• The parameter used to measure growth is increase in fresh weight, dry weight, length, area, and volume and cell number. All parameters are not used for every kind of growth.
• Formative phase is also called as the phase of cell formation or cell division. It occurs at root apex, shoot apex and other region having meristematic tissue. The rate of respiration is very high in the cells undergoing mitosis division in formative phase.
• Phase of Enlargement- newly formed cells produced in formative phase undergo enlargement. Enlarging cells also develops vacuoles that further increase the volume of cell.
• Cell enlargement occurs in all direction with maximum elongation in conducting tissues and fibres.

• Phase of maturation- the enlarged cells develops into special or particular type of cells by undergoing structural and physiological differentiation.
• Growth Rate- increase in growth per unit time is called growth rate. Growth rate may be arithmetic or geometrical.
• Arithmetic Growth- the rate of growth is constant and increase in growth occurs in arithmetic progression- 2,4,6,8 ……. It is found in root and shoot elongation.

L_t = L₀ + rt
Length after time = length at beginning + growth rate x time.

• Geometric Growth- here initial growth is slow and increase rapidly thereafter. Every cell divides. The daughter cells grow and divide and the granddaughter cells that result into exponential growth.
• Geometrical growth is common in unicellular organisms when growing in nutrient rich medium.

• Sigmoid growth curve consists of fast dividing exponential phase and stationary phase. It is typical of most living organisms in their natural environment.

Exponential growth can be represented as follows-
W₁ =W₀e^rt. W1 = final size, W0 = initial size, r = growth rate, t = time of growth and e is the base of natural logarithms (2.71828).

• Quantitative comparison between the growth of living system can be made by

1. Measurement and comparison of total growth per unit time is called the absolute rate.
2. The growth of given system per unit time expressed on a common basis is called relative growth rate.

Condition for growth

• Necessary condition for growth includes water, oxygen and essential elements. Water is required for cell enlargement and maintaining turgidity. Water also provide medium for enzymatic conditions.
• Protoplasm formation requires water and micro and macronutrients and act as source of energy.
• Optimal temperature and other environmental conditions are also essential for growth of the plant.
• Cells produced by apical meristem become specialized to perform specific function. This act of maturation is called differentiation.
• The living differentiated cells that have lost ability of division can regain the capacity of division. This phenomenon is called dedifferentiation. For example interfascicular cambium and cork cambium.
• Dedifferentiated cells mature and lose the capacity of cell division again to perform specific functions. This process is called redifferentiation.

Development
It is the sequence of events that occur in the life history of cell, organ or organism which includes seed germination, growth, differentiation, maturation, flowering, seed formation and senescence.

Sequence of development process in plant cell

• Different structures develop in different phases of growth as well as in response to environment. The ability to change under the influence of internal or external stimuli is called plasticity. Heterophylly in cotton plant is the example of plasticity.

Plant Growth Regulators are simple molecules of diverse chemical composition which may be indole compounds, adenine derivatives or derivatives of carotenoids.

• Auxin was isolated by F.W. Went from tips of coleoptiles of oat seedlings.
• The ‘bakane disease’ of rice seedlings is caused by fungal pathogen Gibberella fujikuroi. E. Kurosawa found that this disease is caused due to presence of Gibberellin.
• Skoog and Miller identified and crystallized the cytokinesis, promoting active substance called kinetin.

Auxin- was first isolated from human urine. It is commonly indole-3-acetic acid (IAA). It is generally produced at stem and root apex and migrate to site of action.
Functions-

1. Cell enlargement.
2. Apical dominance
3. Cell division
4. Inhibition of abscission
5. Induce Parthenocarpy

Gibberellins- are promotery PGR found in more than 100 forms named as GA1GA1, GA2GA2, GA3GA3…. GA100GA100. The most common one is GA3GA3 (Gibberellic Acid).
Functions-

1. Cell elongation.
2. Breaking of dormancy.
3. Early maturity
4. Seed germination.

Cytokinins- the plant growth hormone is basic in nature. Most common forms include kinetin, zeatin, etc. They are mainly synthesized in roots.
Functions-

1. Cell division and cell differentiation.
2. Essential for tissue culture.
3. Overcome apical dominance.
4. Promote nutrient mobilisation.

Ethylene – it is a gaseous hormone which stimulates transverse or isodiametric growth but retards the longitudinal one.
Functions–

1. Inhibition of longitudinal growth.
2. Fruit ripening
3. Senescence
4. Promote apical dominance

Abscisic Acid – it is also called stress hormone or dormin. It acts as a general plant growth inhibitor. Abscisic acid is produced in the roots of the plant and terminal buds at the top of plant.
Function-

1. Bud dormancy
2. Leaf senescence
3. Induce Parthenocarpy
4. Seed development and maturation.

Photoperiodism- the effect of photoperiods or day duration of light hours on the growth and development of plant, especially flowering is called Photoperiodism. On the basis of photoperiodic response, flowering plants have been divided into the following categories-

1. Short Day Plants– they flower when photoperiod is below a critical period (continuous duration of light which must not be exceeded in short day plants and should always be exceeded in long day plants in order to bring them flower). Example- Xanthium, Rice, Sugarcane, Potato etc.
2. Long Day Plants– these plants flower when they receive long photoperiod of light, greater than critical period. Example- Radish, Barley, Lettuce.
3. Day Neutral Plants – the plant can blossom throughout the year. Example- Bean, Wild Kidney.

Vernalisation– is the process of shortening of the juvenile or vegetative phase and hastening of flowering by cold treatment. The stimulus of Vernalisation is perceived by meristematic cells.

• Vernalisation helps in shortening of vegetative period of plant and brings about early flowering.
• It is applicable to temperate plants like Wheat, Rice, Millets, etc.

Class 11 Biology Revision Notes for Respiration in Plants of Chapter 14

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Respiration is an energy releasing, enzymatically controlled catabolic process which involves a step-wise oxidative breakdown of food substance inside living cells.
C6H12O6+6O2→6CO2+6H2O+EnergyC6H12O6+6O2→6CO2+6H2O+Energy

• Living organism require energy for all activities like absorption, movement, reproduction or even breathing. Energy required is obtained from oxidation of food during respiration.
• Cellular respiration is the mechanism of breaking down of food materials within the cell to release energy for synthesis of ATP.
• Breaking down of complex molecules takes place to produce energy in cytoplasm and in the mitochondria.
• Breaking down of C-C bond of complex compounds through oxidation within the cells leading to release of energy is called respiration. The compounds that get oxidized are called respiratory substrates.
• Energy released during oxidation is not used directly but utilized in synthesis of ATP, which is broken down when energy is required. Therefore, ATP is called energy currency of cells.
• The process of respiration requires oxygen. In plants oxygen is taken in by stomata, lenticels and root hairs.
• Plants can get along without respiratory organs because:
  1. Each plant part takes care of its own gas-exchange needs.
  2. Plants do not present great demands for gas exchange.
  3. Distance that gases must diffuse in large plant is not great.
  4. During photosynthesis O2 is released in leaves and diffuse to other part of leaves.

• During process of respiration oxygen is utilized and carbon dioxide and water is released along with energy molecules in form of ATP.
• Respiratory Quotient is the ratio of the volume of carbon dioxide produced to the volume of oxygen consumed in respiration over a period of time. RQ is equal to one for carbohydrate and less than one for protein and peptones.

 
Aerobic Respiration is an enzymatically controlled release of energy in a stepwise catabolic process of complete oxidation of organic food into carbon dioxide and water with oxygen acting as terminal oxidant.

Glycolysis

• The scheme of glycolysis is given by Gustav Embden, Otto Meyerhof, and J. Parnas. It is also called as EMP pathway.
• Glycolysis is the partial oxidation of glucose or similar hexose sugar into two molecules of pyruvic acid through a series of enzyme mediated reaction releasing some ATP and NADH2. It occurs in cytoplasm.
• In plants glucose is derived from sucrose or from storage carbohydrates. Sucrose is converted into glucose and fructose by enzyme invertase.
• Glycolysis starts with phosphorylation of glucose in presence of enzyme hexokinase to form Glucose-6-phosphate. One molecules of ATP is used in this process.
• In next steps Glucose-6-phosphate is converted into fructose-6-phosphate, catalysed by enzyme phosphohexose isomerase.
• Fructose-6-phosphate uses another molecule of ATP to form Fructose-1-6 biphospahte in presence of enzyme phosphfructokinase.

• In glycolysis two molecules of ATP are consumed during double phosphorylation of glucose to fructose 1,6 biphosphate. Two molecules of NADPH2 are formed at the time of oxidation of glyceraldehyde 3-phosphate to 1,3 biphosphoglycerate. Each NADH is equivalent to 3ATP, so that net gain in glycolysis is 8 ATP.
• Pyruvic acid is the key product of glycolysis, further breakdown of pyruvic acid depends upon the need of the cell.
• In animal cells, like muscles during exercise, when oxygen is insufficient for aerobic respiration, pyruvic acid is reduced to Lactic acid by enzyme lactate dehydrogenase due to reduction by NADH2.

• In fermentation by yeast, pyruvic acid is converted to ethanol and CO2. The enzyme involved is pyruvic acid decarboxylase and alcohol dehydrogenase catalyse this reaction.
• In both lactic acid fermentation and alcohol fermentation very less amount of energy is released.
• Yeasts poison themselves to death if concentration of alcohol reaches above 13%.
• Final product of glycolysis, pyruvate is transported from the cytoplasm into mitochondria for further breakdown.
• Oxidation of Pyruvate to Acetyl-CoA is done to produce CO2 and NADH. The reaction catalyzed by pyruvic dehydrogenase requires the participation of several Coenzymes including NAD+ .

Pyruvicacid+CoA+NAD+Pyruvicacid+CoA+NAD+−→−−−−−−−−−−−−−PyruvatedehydrogenaseMg2+AcetylCoA+CO2→PyruvatedehydrogenaseMg2+AcetylCoA+CO2+NADH+H++NADH+H+

• The Acetyl CoA enters a cyclic pathway called TCA cycle or Kreb’s cycle.

Tricarboxylic Acid Cycle/Krebs Cycle

• TCA cycle was discovered by Hans Krebs in 1940. This cycle is called TCA cycle because initial product is citric acid.
• Acetyl CoA combine with OAA ( Oxaloacetic acid) and water to yield citric acid in presence of enzyme citrate synthase to release CoA.
• Citrate is then isomerised to isocitrate. It is followed by two successive
  steps of decarboxylation, leading to the formation of α-ketoglutaric acid and then succinyl-CoA.
• In the remaining steps, succinyl-CoA is oxidised to OAA allowing the cycle to continue.
• There are three points in the cycle where NAD + is reduced to NADH2 and one point where FAD + is reduced to FADH2 .
• A molecule of glucose produces two molecules of NADH2NADH2, 2ATP and two pyruvate while undergoing glycolysis. The two molecules of pyruvate are completely degraded in Krebs cycle to form two molecules of ATP, 8NADH28NADH2 and 2FADH22FADH2.

pyruvic + 4NAD⁺ + FAD⁺ + 2H₂O + ADP + Pi −→−−−−−−−−−−−−MitochondrialMatrix→MitochondrialMatrix 3CO₂ +4NADH+4H+FADH2ATP+4NADH+4H+FADH2ATP
Terminal Oxidation is the name of oxidation found in aerobic respiration that occurs towards end of catabolic process and involves the passage of both electrons and protons of reduced coenzyme to oxygen to produce water.

Electron Transport Chain

• The metabolic pathway through which the electron passes from one carrier to another inside the inner mitochondrial membrane is called ETC or mitochondrial respiratory chain.
• Electrons from NADH produced during citric acid cycle are oxidized by NADH dehydrogenase and electrons are transferred to ubiquinone located within the inner membrane. Ubiquinone also receives electrons from FADH2 which is transferred to cytochrome c via cytochrome bc₁ complex.
• When the electrons pass from one carrier to another via electron transport chain, they produce ATP from ADP and inorganic phosphate. The number of ATP molecules synthesized depends upon electron donor.
• Oxidation of one molecule of NADH gives rise to 3 molecules of ATP, while oxidation of one molecule of FAD2FAD2 produce two molecules of ATP.

Oxidative phosphorylation	Photophosphorylation
a) It occurs in respiration process.  b) Energy of oxidation-reduction is used for production of proton gradient required for phosphorylation.	a) It occurs in photosynthesis.  b) Light energy is utilized for production of proton gradient for phosphorylation.

• The energy released during ETC is used to make ATP with the help of ATP synthase, which consists of two major parts F1 and F0.
• F1 is a peripheral membrane protein complex having site for synthesis of ATP from ADP and inorganic phosphate. F0 is integral membrane protein that form channel for proton.
• For each ATP produced 2H+ passes through F0 from the intermembrane space to the matrix down the electrochemical proton gradient.

Fermentation	Aerobic Respiration
a. It accounts for incomplete oxidation of glucose.  b. In fermentation, there is net gain of only two molecules of ATP. c. NADH is oxidized to NAD+ very slowly.	a. It accounts for complete oxidation of glucose.  b. In aerobic respiration, there is more net gain of ATP. c. NADH is oxidized to NAD+ very fast.

Amphibolic Pathway

• Glucose is the favored substrate for respiration. All carbohydrates are usually converted into glucose before used for respiration.
• Fats needs to be broken down into glycerol and fatty acid, which is further broken converted into Acetyl CoA and enter the respiratory pathway.
• Proteins are broken into amino acids and further enter into Krebs cycle.
• Breaking down process within living organism is called catabolism and synthesis process is called anabolism process. So, respiration is an Amphibolic pathway.

Class 11 Biology Revision Notes for Photosynthesis in Higher Plants of Chapter 13

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Photosynthesis is a physico-chemical process by which green plants use light energy to drive the synthesis of organic compounds. It is an enzyme regulated anabolic process.
6CO2+12H2O−→−−LightC6H12O6+6H2O+6O26CO2+12H2O→LightC6H12O6+6H2O+6O2

• Photosynthesis is the basis of life on earth because it is the primary source of all food on earth and it is responsible for release of O2O2 in the atmosphere.
• Chlorophyll, light and CO2CO2 is required for photosynthesis. It occurs only in green part of leaves and in presence of light.

Early Experiments

• Joseph Priestley in 1770, on the basis of his experiments showed the essential role of air in growth of green plants. A mouse kept in closed space could get suffocated and die but if a mint plant is kept in bell jar neither candle will extinguish nor will the mouse die. He concluded that foul air produced by animal is converted into pure air by plants. Priestley discovered Oxygen gas in 1774.

• Julius Von Sachs in 1854 shows that green part in plants produces glucose which is stored as starch. Starch is the first visible product of photosynthesis.
• T.W.Engelmann (1843-1909) used prism to split light into its components and then illuminated Cladophora (an algae) placed in a suspension of aerobic bacteria. He found that bacteria accumulated in blue and red light of the split spectrum. He thus discovered the effect of different wavelength of light on photosynthesis (action spectrum).
• Cornelius Van Neil (1897-1985) on the basis of studies with purple and green sulphur bacteria showed that photosynthesis is a light dependent reaction in which hydrogen from an oxidisable compound reduces CO2CO2 to form sugar.

2H2A+CO2−→−−Light2A+CH2O+H2O2H2A+CO2→Light2A+CH2O+H2O
In green sulphur bacteria, when H2SH2S , instead of H2OH2O was used as hydrogen donor, no O2O2 was evolved. He inferred that O2O2 evolved by green plants comes from H2OH2O but not from CO2CO2 as thought earlier.
Where Does Photosynthesis Takes Place?

• Chloroplasts are green plastids which function as the site of photosynthesis in eukaryotic photoautotrophs. Inside the leaves, chloroplast is generally present in mesophyll cells along their walls.
• Within the chloroplast there is a membranous system consisting of grana, the stroma lamellae and the fluid stroma.

• The membrane system is responsible for synthesizing light energy for the synthesis of ATP and NADPH. In stroma enzymatic reactions incorporate CO2CO2 in plants leading to synthesis of sugar.
• The reaction in which light energy is absorbed by grana to synthesis ATP and NADPH is called light reaction. The later part of photosynthesis in which CO2CO2 is reduced to sugar, light is not necessary and is called dark reaction.

Pigments involved in Photosynthesis – Chromatographic separation of leaf pigments are as follows-
 
Maximum absorption by chlorophyll a occurs in blue and red regions having higher rate of photosynthesis. So, chlorophyll a is the chief pigment.

• Other thylakoid pigments like chlorophyll b, xanthophyll and carotenoids are called accessary pigments that absorb light and transfer energy to chlorophyll a and protect them from photo-oxidation.

Light reaction

• Light reaction(photochemical phase) includes:

1. Light absorption
2. Water splitting
3. Oxygen release
4. Formation of high energy chemical intermediates (ATP and NADPH).

• The pigments are organized into two discrete LHC( light harvesting complex) within photosystem I and photosystem II.
• LHC are made up of hundreds of pigments molecules containing all pigments except single chlorophyll a molecules in each PS.

• The pigments in photosystem I and photosystem II absorbs the lights of different wavelength. Single chlorophyll a molecule makes the reaction centre. In PS I reaction centre has highest peak at 700nm, hence called P700. And PS II reaction centre has highest peak at 680 nm, so called P680.

The Electron Transport System

• Reaction centre of photosystem II absorbs light of 680 nm in red region and causing electron to become excited. These electrons are picked by an electron acceptor which passes to electron transport system consisting of cytochromes.

• Electrons are passed down the electron transport chain and then to the pigment of PS I.
• Electron in the PSI also get excited due to light of wavelength 700nm and are transferred to another accepter molecule having a greater redox potential.
• When electron passes in downhill direction, energy is released. This is used to reduce the ADP to ATP and NADP+ to NADPH. The whole scheme of transfer of electron is called Z-scheme due to its shape.
• Photolysis of water release electrons that provide electron to PS II. Oxygen is also released during this process.

2H2O→4H++O2+4e−2H2O→4H++O2+4e−

• Difference between cyclic and non-cyclic photophosphorylation

Cyclic photophosphorylation	Non-cyclic photophosphorylation
It is performed by photosystem I independently.An external source of electron is not required.It synthesizes only ATP.It occurs only in stromal or intergranal thylakoids.	It is performed by collaboration of both PS I and PS II.The process requires an external electron donor.It synthesizes ATP and NADH both.It occurs in the granal thylakoids only.

 
Chemiosmotic Hypothesis of ATP FORMATION
This hypothesis was proposed by Mitchell in 1961. ATP synthesis is linked to development of proton gradient across the membrane of thylakoid and mitochondria.
The process that causes development of proton gradient across the membrane is-

1. Splitting of water molecules occurs inside the thylakoid to produce hydrogen ion or proton.
2. As electron passes through the photosystems, protons are transported across the membrane because primary acceptor of electron is located towards the outer side the membrane.
3. The NADP reductase enzyme is located in the stroma side of membrane. Electrons come out from the acceptor of electron of PSI, protons are necessary for reduction of NADP+ to NADP + H+. These protons are also removed from the stroma. This creates proton gradient across the thylakoids membrane along with pH in the lumen.
4. Gradient is broken down due to movement of proton across the membrane to the stroma through trans-membrane channel of F0 of ATPase. One part of this enzyme is embedded in membrane to form trans-membrane channel. The other portion is called F1that protrudes on the outer surface of thylakoid membrane which makes the energy packed ATP.
5. ATP and NADPH produced due to movement of electron is used immediately to fix CO2 to form sugar.

• The product of light reaction used to drive the process leading to synthesis of sugar are called biosynthetic phase of photosynthesis.

Calvin Cycle/C3 cycle/Reductive Pentose Sugar Phosphate Pathway
Malvin Calvin, Benson and their colleagues used radioactive 14C and Chlorealla and Scenedesmus algae to discover that first CO2CO2 fixation product is 3-carbon organic compound (3-phosphoglyceric acid) or PGA. Later on a new compound was discovered which contain 4-carbon called Oxaloacetic Acid (AAO). On the basis of number of carbon atoms in first stable product they are named C3 and C4 pathway.
Calvin cycle can be described under three stages: carboxylation, reduction and regeneration.

• Carboxylation is the fixation of CO2CO2 into 3-phosphoglyceric acid (3-PGA). Carboxylation of RuBP occurs in presence of enzyme RuBP carboxylase (RuBisCO) which results in the formation of two molecules of 3-PGA.
• Reduction is series of reaction that leads to formation of glucose. Two molecules of ATP and two molecules of NADPH are required for reduction of one molecules of CO2CO2. Six turn of this cycle are required for removal of one molecule of Glucose molecules from pathway.
• Regeneration is the generation of RuBP molecules for the continuation of cycle. This process require one molecules of ATP.

Fig-Calvin Cycle/ C3 Cycle

• For every molecules of CO2CO2 entering the Calvin Cycle, 3 molecules of ATP and 2 molecules of NADPH is required. To make one molecules of glucose 6 turns of cycle is completed so total energy molecule required is

In	Out
Six CO2CO2  18 ATP 12 NADPH	One glucose  18 ADP 12 NADP

C4 pathway/Hatch Slack Pathway

• This pathway was worked out by Hatch and Slack (1965, 1967), mainly operational in plants growing in dry tropical region like Maize, Sugarcane, Sorghum etc.
• In this pathway first stable product is a 4-carbon compound Oxaloacetic acid (AAO) so called as C4C4 pathway. C4C4 plants have Kranz Anatomy (vascular bundles are surrounded by bundle sheath cells arranged in wreath like manner), characterized by large no of chloroplast, thick wall impervious to gases and absence of intercellular spaces.
• The primary CO2CO2 acceptor is a 3-carbon molecule Phosphoenol Pyruvate present in mesophyll cells and enzyme involved is PEP carboxylase.
• OAA formed in mesophyll cell forms 4-carbon compound like malic acid or aspartic acid which is transported to bundle sheath cells.
• In bundle sheath cell, it is broken into CO2CO2 and a 3-carbon molecule. The 3-carbon molecule is returned back to mesophyll cells to form PEP.
• The CO2CO2 molecules released in bundle sheath cells enters the Calvin cycle, where enzyme RuBisCO is present that forms sugar.

Photorespiration

• It is a the light dependent process of oxygenation of RuBP and release of carbon dioxide by photosynthetic organs of plants.
• Photorespiration decreases the rate of photosynthesis when oxygen concentration is increased from 2-3% to 21%.
• Presence of light and higher concentration of Oxygen results in the binding of RuBisCO enzyme with O2 to form.

RuBisCO + O2→O2→ PGA + phosphoglycolate
This pathway involves Chloroplast, Peroxisome and Mitochondria. Photorespiration do not occurs in C4C4 plants.

C3 plants	C4 plants
The leaves do not have Kranz anatomy.Photorespiration occurs.RuBisCO is the first acceptor of CO2.PGA is the first stable product.Plants are adapted to all climates.Mesophyll cells perform complete photosynthesis.	The leaves show Kranz anatomy in leaves.Photorespiration does not occur.PEP is the first acceptor of CO2.OAA is the first stable product.Plants are adapted to tropical climate.Mesophyll cells perform only initial fixation.

Factors affecting photosynthesis

1. Light- as light intensity increases, the rate of photosynthesis also increases until light saturation point.
2. Carbon dioxide concentration– with increase in concentration of CO2CO2 rate of photosynthesis increase till the compensation point.
3. Temperature- it does not influence the rate of photosynthesis directly but at higher temperature enzyme activity is inhibited due to denaturation of enzymes which affect the dark reaction.
4. Water– due to increase in amount of water, rate of photosynthesis does not increase proportionally as after saturation no more water is required during photosynthesis.

Blackman’s Law of Limiting Factors states:
If a chemical process is affected by more than one factor, then its rate will be determined by the factor which is nearest to its minimal value: it is the factor which directly affects the process if its quantity is changed.

Class 11 Biology Revision Notes for Mineral Nutrition of Chapter 12

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Mineral nutrition is the study of source, mode of absorption, distribution and metabolism of various inorganic substances (minerals) by plants for their growth, development, structure, physiology and reproduction.
Methods to study the Mineral Requirement of Plants

• Hydroponics is the technique of growing plants in nutrient solution in complete absence of soil. This method is used to determine the nutrients essential for plants.
• In this method plant is cultured in soil-free, defined mineral solution. These methods require purified water and mineral nutrients.
• Essential elements are identified and their deficiency symptoms are discovered by hydroponics methods. It is also used for commercial production of vegetables, like tomato and cucumber.

Essential mineral nutrients- About 65 elements are found in different plants. Following criteria is used to determine the essentiality of an element.

1. Element must be absolutely necessary for the normal growth and reproduction to complete their life cycle.
2. The requirement of element must be specific and not replaceable.
3. Element must be directly involved in the metabolism of plants.

• Macronutrients are present in plants tissues in larger quantity. C, H and O is obtained from water and rest are absorbed from soil.
• Micronutrients or trace nutrients are required in very small quantity.

On the basis of diverse functions, essential elements are divided into following categories-

Role of Macro and Micro nutrients-

1. Essential elements participate in various metabolic processes in plants such as permeability of cell membrane, maintenance of osmotic potential, ETS. Etc.
2. Act as major constituents of macromolecules and co-enzymes.

Various forms and function of essential nutrients-

1. Nitrogen- required by plants in greatest amount, it is absorbed by plants as NO₂^–, NO₃^– and NH₄⁺ . It is one of the major constituent of proteins, nucleic acids and vitamins.
2. Phosphorus- Absorbed by plants from soil in the form of phosphate ions. It is the constituent of cell membrane. All nucleic acids and nucleotides require phosphorus.
3. Potassium – absorbed as potassium ions (K⁺). Help to maintain cation-anion balance in cells. It is involved in protein synthesis, opening and closing of stomata.
4. Calcium – absorbed by plants from soil in form of Calcium ions (Ca²⁺). Used in synthesis of cell wall. It activates certain enzymes.
5. Magnesium- absorbed by plants in form of Mg²⁺ ions. It activates the enzymes for respiration, photosynthesis, and involved in synthesis of DNA and RNA. It is constituent of chlorophyll.
6. Sulphur- plants obtain sulphur in form of sulphate (SO₄^2-). Present in amino acids (cysteine, methionine) and is main constituent of coenzymes and vitamins.
7. Iron- obtained in the form of ferric iron (Fe³⁺). It is important constituent of protein involved in transport system.
8. Manganese-absorbed in form of Mn²⁺ ions. Main function is splitting of water to liberate Hydrogen and Oxygen during photosynthesis.
9. Zinc-obtained as Zn²⁺ ions. Activate enzymes like carboxylases. Needed in formation of Auxin.
10. Copper –absorbed as cupric ions(Cu²⁺). Involved in various metabolic activities and redox reactions.
11. Boron-absorbed as BO₃^3- or B₄O₇^2- ions. Required for uptake of calcium, cell elongation and pollen germination.
12. Chlorine – it is absorbed in form of Cl^– ions. Determine the solute concentration and splitting of water during photosynthesis.

Deficiency Symptoms of Essential elements

• When supply of essential elements becomes limited, plant growth is retarded. The concentration of essential elements below which plant growth is retarded is called critical concentration.
• In absence of any particular element, plant shows certain morphological changes. These morphological changes are called deficiency symptoms.
• The parts of plant that show deficiency symptoms depend upon mobility of elements in the plants. Elements that are actively mobilized (N,Mg,K) show deficiency in older regions. On the other hand, symptoms appear first in young region if the elements are relatively immobile (Ca) and not transported out of mature tissues.
• Kinds of deficiency syndrome are as follows-

Deficiency Disease	Symptoms	Deficient elements
Chlorosis	Loss of chlorophyll leading to yellowing of leaves.	N, K, Mg, S, Fe, MN, Zn, Mo
Necrosis	Death of tissue (leaf).	Ca, Mg, Cu, K.
Stunted plant growth	Less height of plant	Fe, K.
Premature fall of leaves and buds.	Falling of leaves and buds.	P, Mg, Cu
Inhibition of cell division	Less elongation in stem.	Low level of N, K, S, Mo.

• Deficiency of any element may cause many symptoms or same symptoms may be caused by different elements. To identify the deficient elements various symptoms are compared with standard chart.Toxicity of micronutrients- in higher doses, micronutrients become toxic. Any tissue concentration which reduces dry weight of tissue by 10% is called toxic concentration. Critical toxic concentration is different for different elements.
  Mechanism of absorption of elements
• It takes place in two phases. In first phase, rapid intake of ions occurs in free space or outer space of the cells, apoplast. In second phase, ions are taken slowly into inner space, the symplast of the cells.
• Passive movement of ions in apoplast occurs through ion channels and trans-membrane protein. On the other hand, movement of ions into symplast occurs by expenditure of energy by active process.
• The movement of ion is called flux. The inward movement is called influx and outward movement is called efflux.

• Translocation of solutes occur through xylem along with ascending stream of water

Soil as reservoir of essential elements- most of the nutrients required for growth and development is obtained from soil by roots. These minerals are formed by weathering of rocks. Soil also harbours nitrogen fixing bacteria and other microbes, holds water and supplies air to roots. Deficiency of essential elements affects the crop yield. So, fertilisers are used to supplement these elements.
Metabolism of Nitrogen

• Nitrogen is the most prevalent element in living world along with C, H and O. It is the main constituent of proteins, nucleic acids, fats, hormones, enzymes etc.
• The process of conversion of nitrogen to ammonia is called nitrogen fixation. In nature lightening and ultraviolet radiation provide energy to convert atmospheric nitrogen into nitrogen oxide ( No, NO₂ and N₂O).
• Industrial combustion, forest fire and automobiles along with thermal power plants produce nitrogen oxides.
• The decomposition of organic nitrogen of dead plants and animals into ammonia is called ammonification.
• Ammonia is first oxidized to nitrite by bacteria Nitrosomonas or Nitrococcus which is further oxidized to nitrate with help of bacteria Nitrobactor. These processes are called nitrification.

2HN3+3O2→2NO−2+2H++2H2O2NO−2+O2→2NO−32HN3+3O2→2NO2−+2H++2H2O2NO2−+O2→2NO3−

• Nitrates formed is absorbed by plants and transported to leaves. Nitrates is converted into free nitrogen by the process called denitrificaion by bacteria Pseudomonas and Thiobacillus.
• Reduction of nitrogen to ammonia by living organism is called Biological Nitrogen Fixation. The enzyme nitrogenase is present in prokaryotic organism called nitrogen fixer.

N≡N−→−−−−−−NitrogenaseNH3N≡N→NitrogenaseNH3

• Nitrogen fixing microbes may be symbiotic (Rhizobium) or free living (Nostoc, Azotobactor, Anabaena).
• Symbiotic biological nitrogen fixation includes legume-bacteria relationship in which rod shaped Rhizobium lives with symbiotic relation with nodules of Leguminous plants.
• Central portion of nodule is pink or red due to presence of leguminous haemoglobin or leg-haemoglobin.

Nodule formation involves sequence of interaction between root and Rhizobium as follows-

• Rhizobia increase in number and attach with epidermis of roots. Root hairs curls and bacteria invade it. An infection thread is formed that carries the bacteria into cortex of root.
• Nodule formation starts in cortex of root. Bacteria is released from thread to cells which leads to formation of specialized nitrogen fixing cells.
• Nodules establish direct vascular connection with host for exchange of nutrients.
• Nodule contains all necessary biochemical components like enzyme nitrogenase and leg-haemoglobin.

• Enzyme nitrogenase is a Mo-Fe protein and catalyses the conversion of atmospheric nitrogen into ammonia.

The reaction is as follows-
N2+8e−+8H++16ATPN2+8e−+8H++16ATP→2NH3+H2+16ADP+16P1→2NH3+H2+16ADP+16P1

• The enzyme nitrogenase is highly sensitive to molecular oxygen and needs anaerobic condition. To protect this enzyme from oxygen, the nodules contain an oxygen scavenger called leg-haemoglobin.
• The ammonia synthesized by nitrogenase enzyme require large amount of energy (18ATP) for each NH3 produced.

Fate of ammonia- at physiological pH, ammonia is converted into ammonium ions (NH₄⁺).It is toxic for plants in larger concentration and ammonium ion is converted into amino acids by two methods-

1. Reductive amination– in this process ammonia reacts with α-ketoglutaric acid to form glutamic acid.

α−ketoglutaricacid+NH+4+NADPHα−ketoglutaricacid+NH4++NADPH−→−−−−−−−DehydrogenaseGlutamateglutamate+H2O+NADP→DehydrogenaseGlutamateglutamate+H2O+NADP

1. Transamination– it involves the transfer of amino group from amino acids to keto group of keto acid. Glutamic acid is the main amino acid from which transfer of NH3 takes place and other amino acids are formed by transamination. The enzyme transaminase catalyses all such reactions.

Two important amides asparagine and glutamine found in plants as structural part of proteins. They are formed from aspartic acid and glutamic acid by addition of another amino group to it.