Respiration (Botany)

RESPIRATION (BOTANY) Respiration is one of the important characteristic of life. It is defined as “oxidation of food (with or without oxygen) with release of energy and with or without CO2.” Types of Respiration:- Two kinds Anaerobic Respiration Aerobic Respiration O 2 It requires molecular Oxygen. is not required. Food is fully oxidized Food is partially oxidized. CO CO 2 2 is released may or may not be released. Much more energy is released(38 ATP) Less energy is released.(2 ATP) It takes place in three steps such as It takes place in two steps such as Glycolysis Glycolysis , Krebs Cycle and ETS and It occurs in cytoplasm and mitochondria of eukaryotes. Pyruvic acid into Organic acid. It occurs in cytoplasm of prokaryotes and eukaryotes. Aerobic Respiration. It occurs in higher plants and animals in three steps.-Glycolysis, Krebs Cycle and Electron Transport System. Q. What is Glycolysis? Discuss various stepes of Glycolysis and write its significance. Ans.:- Glycolysis (Glucose break) is a common pathway for all kinds of respiration. It is also called EMP path way according to the name of its discoverers such as Embden, Meyerhoff and Paranas. Glycolysis takes place in cytoplasm of cell without oxygen. During glycolysis one molecule of glucose breaks into two molecules of pyruvic acids. Mechanism of Glycolysis:Glycolysis takes place in 10 consecutive steps and catalyzed by several enzymes. Glycolysis is completed in two phases such as- Preparatory phase Pay off phase Preparatory Phase:In this phase glucose molecule breaks into dihydroxy acetone 3-phosphate and glyceraldehydes 3-phosphate in five steps. Phosphorylation -I Isomerization -I Phosphorylation -II Splitting Isomerisation -II Pay off Phase :Dehydrogenation and phosphorylation -III Synthesis of ATP-I Isomerisation -III Dehydration Synthesis of ATP-II Glycolysis is a common pathway for all types of respiration. One molecule of Glucose is converted into two molecules of Pyruvic acids. Generally 2 molecules of ATP are produced (8 molecules of ATP when O 2 available). Glycolysis is a continuous process. Q. what is TCA cycle? Describe various steps of TCA cycle and write its significance. Answer: In most eukaryotic cells respiratory break down of pyruvic acid occur within matrix of mitochondria. This break down occurs in a cyclic pathway known as TCA (tricarboxylic acid)cycle/Citric acid cycle/Krebs cycle. This cycle was first reported by German chemist Sir Hans Krebs in 1937 and got Nobel Prize in1953. The oxidation of Pyruvic acid occurs in two main steps. Formation of Acetyl C o. A Krebs cycle A] Formation of Acetyl Co. A Pyruvic acid is a three carbon compound. It can not enter into mitochondria directly through inner membrane. It must be converted into a two carbon compound Acetyl Co. A to enter into Krebs cycle. C3H4O3 + Co. A + NAD----------------------------------- Acetyl Co. A + Co2 + H2O +NADH2 B] Krebs Cycle Acetyl Co. A is completely oxidized in matrix of mitochondria in following steps. Condensation: Acetyl Co. A + Oxaloacetic acid + H2O-------------------------------- 2 Citric acid + Co. A Dehydration: Citric acid ------------------------------- Cis-Aconitic acid + H2O Hydration: Cis-Aconitic acid + H2O --------------------------- Isocitric acid Dehydrogenation I: Isocitric acid + NAD ----------------------------- Oxalosuccinic acid + H2O + NADH2 Decarboxylation : Oxalosuccinic acid ------------------------------ Ketoglutaric acid + CO2 Decarboxylation and Dehydrogenation II : Ketoglutaric acid + Co. A + NAD -------------------------------- Succinyl Co. A + NADH2 +CO2 +H2O Formation of ATP Succinyl Co. A + GDP/ADP +H2O + H3PO4------------------------------------ Succinic acid + Co. A + GTP/ATP Dehydrogention III: Succinic acid +FAD ---------------------------------------- Fumaric acid + FADH2 +H2O Hydrogenation: Fumaric acid +H2O --------------------------------------- Malic acid Dehydrogenation IV: Malic acid + NAD ------------------------------------------- Oxaloacetic acid + NADH2 +H2O Analysis of Krebs Cycle For one glucose molecule Krebs Cycle operates twice. Acetyl Co. A is completely oxidized in Krebs Cycle . In one Krebs Cycle 5 molecules of H2O are released & 4 molecules of H2O used. Two molecules of CO2 are released. One molecule of FADH2 is released. Three molecules of NADH2 are released. One molecule of ATP/GTP is released. Significance All kinds of food like Proteins, Carbohydrates and Fats are oxidized through Krebs Cycle . The Krebs Cycle has dual role: Catabolism: On one hand Pyruvic acid is oxidized. Anabolism: On the other hand some amino acids & fatty acids are synthesized. Energy yield in Krebs Cycle is used in various activities of the cell. Q. Whatis enzyme? Discuss the mechanism/mode of enzyme action in living cell. Answer.- Enzymes are biocatalysts, protein in nature. The word enzyme was coined by F.W. Kuhne 1878. Enzymes may be endoenzume or exoenzyme.Enzymes are very specific and colloidal in nature. Enzymes have active site for substrate and some are allosteric enzymes. Enzyme actionDuring action, enzyme combines with substrate at active site to form enzyme substrate complex. This complex is unstable and soon break to form product and enzyme becomes free. E + S --------- ES --------- E + P Enzyme Substrate Enzyme Enzyme Product Substrate Complex Activation energyActivation energy is that energy which required by the substrate to take part in a biochemical reaction. This activation energy is lowered in presence of enzyme. Mode of Enzyme action. Several theories have been proposed such asLock and Key Theory Induced fit Theory Lock and Key TheoryEmil Fischer 1890 proposed this theory which states that the rigid active site of enzyme has accommodate the substrate to form enzyme substrate complex like a specific key fits into a lock. The enzyme substrate complex soon breaks to form the product and active site of enzyme becomes free to pick up new substrate. E+S ES--------- E + P Evidence- Competitive inhibition supports this theory in which a substrate analogue blocks the catalytic site of enzyme. Induced fit TheoryThis theory was proposed by Koshland (1959). According to this theory substrate induces a conformational change in the active site of enzyme so that substrate fits with it to form enzyme substrate complex. This complex breaks to form the product and enzyme regain to original shape. Evidence- X-ray diffraction and optical rotation analysis supported the conformational change in catalytic site. Michaelis and Menten conceptThey postulated that enzyme first combines reversibly with substrate to form enzyme substrate complex that breaks in a slower process to form product and enzyme. K1 K2 E + S ES------------ E + P K-1 K = Rate of reaction. Bisubstrate enzyme actionFirst order or unisubstrate reactions are common. But majority (60%) enzymatic reactions are second order or bisubstrate reactions in which 2 substrates react to form 2 products. E A+BP+Q Factors affecting enzyme actionTemperature- optimum temperature is 35-40 C for most enzymes. Enzyme activity decreases at very low or high temperature. pH – optimum pH for most enzyme is pH7.0. A shift in pH decreases the rate of enzyme reaction. Substrate concentration- With increase in Substrate concentration the rate of reaction increases but at very high concentration the rate of reaction remain constant due to saturation of enzyme. Enzyme concentration- With increase in enzyme concentration the rate increase but at high concentration enzyme activity decrease due to limited substrate. Inhibitors - these are drugs or toxins which reduce or stop enzyme action. These are of two types- Reversible and irreversible. Reversible- these are Non-Competitive or Allosteric inhibitors which stop enzyme ac tivity. Irreversible- these are competitive or un competitive inhibitors that stop enzyme activity. Q. Describe the structure and function of human brain. Amnswer- Human brain is the part of central nervous system. It weighs about 1400gms and volume of about 1500c.c. it is enclosed in a bony case called cranium. Meninges- the brain is surrounded by three membranes called meninges. Outer Duramater Middle Arachnoid Inner Piamater The subdural space and subarachnoid space are filled with cerebrospinal fluid that protects the brain from external shock and exchange nutrients and waste products between nervous tissue and blood. Brain is formed of outer Grey matter and inner White matter. Parts of brainBrain or encephalon is a white, bilaterally symmetrical structure with three parts. Fore brain or prosencephalon Mid brain or Mesence phalon Hind brain or Rhombencephalon FORE BRAIN:It is the largest anterior part of brain with three parts.- Olfactory lobes, cerebral hemispheres and diencephalon. Olfactory Lobes- it consists of olfactory bulb and olfactory tract with not well marked rhinocoel . It is the centre of smell. Cerebral hemispheres / Cerebrum- it is the largest part of brain (about 2/3) it is divided into right and left cerebral hemispheres by deep longitudinal median groove and both hemispheres are connected by transverse nerve fibres called corpus callosum with genu and splenium . The cerebral hemispheres are divided by 3 deep fissures into 4 lobesFrontal lobe has two areasMoter area-controls voluntary movement of muscle and premotor area controls the involuntary movements of muscles. Parietal lobesomesthetic area for sensation like pain , touch and temperature. Temporal lobe – for interpretation of sound, language, memory and emotion. Occipital lobe- it has visual area for vision and auditory area for hearing sensations. On ventral side there is a longitudinal fissure called rhinal fissure which separates hippocampal lobe from pyriform lobe in each hemisphere. There is small lobe named Insula or island of Reil covered by parietal, frontal and temporal lobes. The outer layer of cerebral hemisphere is called cerebral cortex or neopallium with cerebral nuclei. The cortex is convoluted with ridges (gyri) and depressions (sulci). The cavities within the cerebral hemispheres are called lateral ventricles or paracoeles(1st and 2nd ventricles) which open to third ventricle ( cavity of diencephalon) by foramen of Monro. FunctionGovern mental abilities like memory, learning, intelligence, thinking etc. It control laughing and weeping. It responds to pain, touch, cold etc in somaethetic area. Controls voluntary and spontaneous actions. Interprets various stimuli. Diencephalon- it is last part and covered by cerebral hemisphere. Dorsally it bears a pineal stalk with a rounded pineal body. its cavity is called diocoel (third ventricle). On ventral side hypothalamus forms the floor of diocoel . The pituitary hangs below the hypothalamus by a stalk called infundibulum . Below pituitary is mammillary body. in front of pituitary there is optic chiasma . It regulates emotion and recognizes heat, cold and pain Hypothalamus controls carbohydrates and fat metabolism,blood pressure Epiphysis or pineal body secret melatonin that control pigmentation in some animals. Epiphysis function as Biological clock. MID BRAIN It consists of two partsOptic lobes- there are 4 solid optic lobes on dorsolateral side collectively called corpora quadrigemina . They are formed of grey matter. They act as visual( anterior pair) and auditory reflex(posterior pair). Crura cerebri it connects medulla oblongata with cerebral hemisphere. It controls activities of eye muscle. HIND BRAIN It has two parts- cerebellum and brain stem. Cerebellumit is the second largest part of brain and formed of outer cerebellar cortex( grey matter) and central medulla(white matter). It has 3 lobescentra vermis , two lateral lobes and two floccular lobes. The grey matter forms a tree like arbor vitae. Cerebellum maintains equilibrium and controls posture. Brain stemit has two parts. Pons varoli - it is thick bundles of transverse nerve fibres that connect two sides of cerebellum. It coordinates muscle movement on two sides of body. Medulla oblongata- It continues behind as spinal cord. I t has 4 th ventricle or metacoel . It controls all involuntary actions of body. it has cardiac centre(regulate heart beat), respiratory centre(control breathing), gastric centre( control flow of gastri juice), reflex centre(control swallowing, vomiting, salivation etc). Q. what is electrone transport system (ETS). Discuss ETS and calculate how much energy is produced from one Glucose molecule. Answer:Terminal oxidation is the final step of aerobic respiration which involves two processes – Electrone transport and Oxidative phosphorylation. During oxidation of Glucose in aerobic respiration 10 NADH and 2 FADH2 molecules are produced. During terminal oxidation, oxidation of each NADH produces 3ATP while oxidation of one FADH2 prproduces 2ATP. Electron transport System :it is a series of coenzymes and cytochromes through which electrons pass from one carrier to another. It is located in inner mitochondrial membrane. It consists of 5 protein complexes- I to V. Complex-I: it is also called NADH dehydrogenase complex. It contains FMN and Fe-S. Complex-II: it is also called Succinate –Q reductase . It is peripheral and can not act as proton pump. It consists of Fe-S, cytochrome b 560 and succinate dehydrogenase . Complex- III: Cytochrome reductase or b-c 1 complex. Complex-IV: it is also called Cytochrome oxidase . It contains copper atoms. Complex-V: it is also called ATP synthase or oxysome or F0-F1 particle Mobile electron carriers- 2 types Ubiquinone (UQ )it is present between complex I, complex II & complex III. Cytochrome C- it is present between complex III & IV. Electron flow:There are two routs of electron flow. First rout :It consists of NADH complex- I, UQ, complex-III, Cytochrome C , complex-IV & V. The electron is finally received by molecular oxygen to form water. Second route :This route is for electron from FADH 2 , complex-II, UQ, complex-III, Cytochrome C , complex-IV & V. the electron is finally received by molecular oxygen to form water. Oxidative phosphorylation :It is the synthesis of ATP by Pi with the energy liberated from oxidation of NADH and FADH2. Chemiosmotic hypothesis:This hypothesis was proposed by Piter Mitchell 1961. According to this hypothesis, during electron flow protons (H+) are pumped from matrix to inter membrane space of Mitochondria. Complex-I is associated with pumping of 4H+, complex-III 4H+ & complex –IV 2H+. In this condition H+ concentration becomes more in inter membrane space than the matrix of mitochondria. This difference in H+ between inter membrane space & matrix is called Proton motive force (PMF) which is about 0.22 Volt or 5.2 K.Cal/Mol / proton. Synthesis of ATP:- This PMF provides sufficient free energy for synthesis of ATP. According to Peter Mitchell H+ slowly returns back to matrix through F0-F1 ATPase complex (complex-V or oxysome). During return phosphorylation takes place & ATP is synthesized. 4H+ are associated for synthesis of one ATP. Electron flow from NADH produces 2.5 ATP in 1st rout & from FADH2 produces 1.5 ATP in 2nd rout. Shuttle system:- This system is for NADH of glycolysis which enters into mitochondria for oxidation. There are two types of shuttle systems such asMalate aspartate shuttle (MA shuttle )it is more efficient and produces 2.5 ATP through 1 st rout. Glycerol phosphate shuttle (GP shuttle )it is less efficient and produces 1.5 ATP through 2 nd rout. Energy calculation for one glucose molecule STEPS MA shuttle GP shuttle Plant cell Animal cell Q- Describe the digestive system of frog with diagram. The digestive system of frogs is made of the following parts. It consists of Mouth, oesophagus, buccal cavity, stomach, intestine, cloaca, rectum,cloacal aperture. Mouth: The digestive system of frogs begins from the mouth and ends at the cloaca. Mouth is an wide opening which leads into the oral cavity or buccal cavity. Buccal cavity: The roof of the buccal cavity consists of teeth which are homodont and polyphyodont not used for mastication as the prey is swallowed whole. It has a large bilobed muscular tongue which is free behind and fixed in the front. The buccal cavity leads to the oesophagus or food pipe. Oesophagus: Short muscular tube that leads into the stomach. Stomach: Stomach is wide and slightly curved, contains the gastric glands that help in digestion of proteins. Intestine: The first part of the intestine is duodenum and then ileum. The ileum has many folds on the inner surface to increase the area for absorption. Rectum: The ileum leads to the rectum. Cloaca: The last part of the rectum is cloaca where undigested food is present. Cloacal aperture: The aperture of the cloaca that opens to the outside of the body is called cloacal aperture. Final answer: Mouth? Buccal cavity?Oesophagus? Stomach? Intestine? Rectum? Cloaca? Cloacal aperture. Reproductive System of Frog The reproductive system of frogs is unisexual. Male frogs are bigger compared to female frogs. Also, male frogs have vocal cords, whereas female frogs do not have them. Male reproductive organs: It consists of the testis, vasa deferentia, seminal vesicle and urinogenital ducts. Testis – Male frogs have pairs of testes that are pale in colour and oval in shape. The testis is covered by the peritoneum fixed to the wall of the kidney. Each testis has coiled filaments called seminiferous tubules that are connected by connective tissue. Each tubule is covered by a membrane. The seminiferous tubules produce spermatozoa Vasa deferentia – A combination of 10 to 12 ducts arise from the testes and are covered by the connective tissue. A group of ducts is called rete testis Seminal vesicle – Seminal vesicle is the portion where sperms are stored until copulation takes place. It consists of fructose that gives nutrients to the sperms Urino genital ducts – This is also called the ureter . Here, sperm is passed out along with urine Sperm formation – The formation of the stem is known as spermatogenesis. It consist of four phaseMultiplication phase, Growth phase, Maturation phase, and Metamorphosis Female reproductive organs: It consists of a pair of ovaries, oviduct, oviduct funnel, middle region and uterus. Ovary – A pair of darkcoloured organs are surrounded by a membrane called mesovarium . Th e ovary is filled with eggs. Ovum is also called an egg. During ovulation, ova come out of the abdomen Oviduct – The oviduct is a slender and elongated duct that connects to the kidneys Oviduct funnel – From the oviduct, a wide opening is situated near the lungs. This broad opening is also called ostium Uterus – It is the thin-walled structure that appears near the cloaca . After ovulation, the egg passes from the ovary with a fluid called the coelomic fluid. The ova are covered by a protein called albumin and reach into the uterus Egg formation – The maturation of the egg requires a few steps: the multiplication phase, the growth phase and the maturation phase Copulation – Male frogs wrap their hands around the female frogs during the mating process. The female frogs deposit the eggs and the male frogs fertilise the eggs, which further hatch into tadpoles and later develop into froglets. Fig.- Female reproductive system of frog. Excretory System : The human excretory system organs include: A pair of kidneys, A pair of ureters , A urinary bladder, and A urethra Kidneys:Kidneys are bean-shaped structures located on either side of the backbone (between transverse processes of T12-L3 vertebrae ) and are protected by the ribs and muscles of the back. Each human adult kidney has a length of 10-12 cm, a width of 5-7 cm, and weighs around 120170g. It is the main excretory organ in humans. The kidney filters the blood and excretes waste along with water in the form of urine. The kidneys have an inner concave structure. The blood vessels (renal artery and renal vein), ureter , and nerves enter the kidneys through the hilum , which is a notch at the inner concave surface of the kidney. The renal pelvis, a large funnel-shaped space present inner to the hilum , has many projections known as calyces. Ureter:- A pair of thin muscular tubes called the ureter comes out of each kidney extending from the renal pelvis. It carries urine from the kidney to the urinary bladder. Urinary bladder:It is a muscular sac-like structure, which stores urine. The urinary bladder is emptied by the process of micturition , i.e. the act of urination. Urethra:This tube arises from the urinary bladder and helps to expel urine out of the body. In males, it acts as the common route for sperms and urine. Its opening is guarded by sphincter muscles. Solution Verified by Toppr The human excretory system comprises the following structures: two bean-shaped kidneys, two ureters, one urinary bladder, and one urethra. Kidneys: Kidneys are the main organ of the human excretory system. The kidneys are paired organs and are located one on each side of the spine at the level of the liver. They are divided into three regions. The renal cortex is the outer layer, the renal medulla is the inner layer and the renal pelvis is responsible for carrying the urine from the kidney to the ureter. The functional unit of a kidney is called the nephron. Ureter:? There is one ureter that comes out of each kidney as an extension of the renal pelvis. The ureter is a thin muscular tube that carries urine from the kidneys to the bladder. Urinary bladder: The bladder receives urine from the ureters, one from each kidney. It is a sac-like structure that is lined with a smooth muscle layer and is responsible for storage of urine till it is expelled from the body by micturition (urination). Urethra: The urethra is a tube that arises from the urinary bladder and expels urine by micturition. The urethra is shorter in females and longer in males. In males, the urethra functions as a common path for sperms and urine. The opening of the urethra is guarded by a sphincter that is voluntary. Q. Describe excretory system of man. The human excretory system comprises the following structures: two bean-shaped kidneys, two ureters , one urinary bladder, and one urethra. Kidneys: Kidneys are the main organ of the human excretory system. The kidneys are paired organs and are located one on each side of the spine at the level of the liver. They are divided into three regions. The renal cortex is the outer layer, the renal medulla is the inner layer and the renal pelvis is responsible for carrying the urine from the kidney to the ureter. The functional unit of a kidney is called the nephron. What is Nephron? A nephron is the basic structural and functional unit of the kidney. They are the microscopic structure composed of a renal corpuscle and a renal tubule. The word nephron is derived from the Greek word – nephros, meaning kidney. There are about millions of nephrons in each human kidney. Structure of Nephron The mammalian nephron is a long tube-like structure, its length varying from 35–55 mm long. At one end, the tube is closed, folded and expanded, into a double-walled, a cuplike structure called the Bowman’s capsule or renal corpuscular capsule, which encloses a cluster of microscopic blood vessels called the glomerulus. This capsule and glomerulus together constitute the renal corpuscle. The structure of nephron comprises two major portions: Renal Tubule Renal Corpuscle Renal Tubule The renal tubule is a long and convoluted structure that emerges from the glomerulus and can be divided into three parts based on function. The first part is called the proximal convoluted tubule (PCT) due to its proximity to the glomerulus ; it stays in the renal cortex. The second part is called the loop of Henle , or nephritic loop because it forms a loop (with descending and ascending limbs) that goes through the renal medulla. The third part of the renal tubule is called the distal convoluted tubule (DCT) and this part is also restricted to the renal cortex. The capillaries of the glomerulus are enclosed by a cup-like structure called Bowman’s capsule. This structure extends to form highly coiled tubules called PCT. PCT continues to form the loop of Henle which ascends to DCT, which in turn opens into the collecting duct. The major function of tubules is reabsorption and the process can either be through active transport or passive transport. In addition, secretions by tubules help in the urine formation without affecting the electrolyte balance of the body. Proximal Convoluted Tubule (PCT) The blood brought by the renal artery is filtered by the glomerulus and then passed to the PCT. Maximum reabsorption takes place in PCT of the nephron.PCT is the region of renal tubule where reabsorption of essential substances like glucose, proteins, amino acids, a major portion of electrolytes and water takes place. The surface area for reabsorption is facilitated by the lining of the simple cuboidal epithelium in them. Reabsorption takes place at the expense of energy, i.e., the process is active.PCT selectively secretes ions such as hydrogen, ammonia, and potassium into the filtrate and absorbs HCO3–from it. Thus, PCT maintains the electrolyte and acid-base balance of the body fluids. Henle’s Loop Henle’s loop has a descending and an ascending limb. Being parts of the same loop, both the descending and ascending limbs show different permeability. The descending limb is permeable to water but impermeable to an electrolyte, while the ascending limb is permeable to electrolytes but impermeable to water. Since the electrolytes get reabsorbed at the ascending loop of Henle, the filtrate gets diluted as it moves towards the ascending limb. But reabsorption is limited in this segment. Distal Convoluted Tubule (DCT) The DCT, which is the last part of the nephron, connects and empties its contents into collecting ducts that line the medullary pyramids. The collecting ducts amass contents from multiple nephrons and fuse together as they enter the papillae of the renal medulla. Similar to PCT, DCT also secretes ions such as hydrogen, potassium, and NH3 into the filtrate while reabsorbing the HCO3–from the filtrate. Conditional reabsorption of sodium ions and water takes place in DCT. Thus, it maintains the pH and sodium-potassium level in the blood cells. Collecting Duct Collecting duct is a long, straight tube where H+ and K+ ions are secreted to maintain the electrolyte balance of the blood. This is also the region where the maximum reabsorption of water takes place to produce concentrated urine. Renal Corpuscle The renal corpuscle consists of a glomerulus surrounded by a Bowman’s capsule. The glomerulus arises from an afferent arteriole and empties into an efferent arteriole. The smaller diameter of an efferent arteriole helps to maintain high blood pressure in the glomerulus. The Bowman’s capsule is divided into three layers: Outer Parietal layer: It is made up of epithelial cells with minute pores of diameter 12nm. Middle Basement membrane: This layer is selectively permeable. Inner Visceral Layer: It consists of large nucleated cells called podocytes which bear finger-like projections called podocel . Types of Nephron There are two types of nephron: Cortical nephron These are the nephrons present within the cortex. These are short and comprise about 80% of the total nephrons. Juxtamedullary nephron These have long loops of Henle and extend into the medulla. These are about 20%. Functions of Nephron The primary function of nephron is removing all waste products including the solid wastes, and other excess water from the blood, converting blood into the urine, reabsorption, secretion, and excretion of numerous substances. As the blood passes through the glomerulus with high pressure, the small molecules are moved into the glomerular capsules and travel through a winding series of tubules. The cell present in each tube absorbs different molecules excluding the glucose, water, and other beneficial molecules which are called as the ultrafiltrate. As the ultrafiltrate molecules travel down the tubules they become more and more hypertonic, which results in more amount of water to be extracted from the ultrafiltrate before it exits the nephrons. The blood surrounding the nephron travels back into the body through the renal blood vessels, which are free of toxins and other excess substances. The obtained ultrafiltrate is urine, which travels down via the collecting duct to the bladder, where it will be stored and released through the urethra. Also Read: Urine Formation And Osmoregulation Ureter:? There is one ureter that comes out of each kidney as an extension of the renal pelvis. The ureter is a thin muscular tube that carries urine from the kidneys to the bladder. Urinary bladder: The bladder receives urine from the ureters, one from each kidney. It is a sac-like structure that is lined with a smooth muscle layer and is responsible for storage of urine till it is expelled from the body by micturition (urination). Urethra: The urethra is a tube that arises from the urinary bladder and expels urine by micturition. The urethra is shorter in females and longer in males. In males, the urethra functions as a common path for sperms and urine. The opening of the urethra is guarded by a sphincter that is voluntary. Excretory System Organs The human excretory system removes nitrogenous waste : A pair of kidneys A pair of ureters A urinary bladder A urethra Kidneys Kidneys are bean-shaped structures located on either side of the backbone and are protected by the ribs and muscles of the back. Each human adult kidney has a length of 10-12 cm, a width of 5-7 cm and weighs around 120-170g. The kidneys have an inner concave structure. The blood vessels, ureter and nerves enter the kidneys through the hilum, which is a notch at the inner concave surface of the kidney. The renal pelvis, a large funnel-shaped space is present inner to the hilum, is has many projections known as calyces. Structure of Kidney The structure of the kidney is explained below: Capsule The outer layer is called the capsule. Inside the kidney, there are two zones- the outer zone is the cortex and the inner zone is the medulla. The cortex extends in between the medullary pyramids as renal columns called columns of Bertin. Nephrons Nephrons are the functional units of the kidney. Each nephron has two parts- glomerulus and renal tubule. Glomerulus consists of a bunch of capillaries formed by afferent arterioles. Blood from glomerulus is carried away by efferent arterioles. The renal tubule starts with a cup-like structure called Bowman’s capsule and this encloses the glomerulus. The malpighian body consists of glomerulus and Bowman’s capsule. The highly coiled structure in the tubule next to the Bowman’s capsule is the proximal convoluted tubule. Henle’s loop The next part of the tubule is Henle’s loop which has an ascending and a descending limb. The ascending loop continues as a distal convoluted tubule. The distal convoluted tubules of many nephrons open into the collecting duct. The cortical region of the kidney comprises of malpighian corpuscle, proximal convoluted tubule and distal convoluted tubule and the medullary region contains a loop of Henle. There are two types of nephrons – cortical and juxtamedullary. In the case of cortical, the loop of Henle is very short and extends only a little into the medulla. In juxtamedullary, the loop of Henle is very long and runs deep into the medulla. Ureter A pair of thin muscular tubes called the ureter comes out of each kidney extending from the renal pelvis. It carries urine from the kidney to the urinary bladder. Urinary Bladder It is a muscular sac-like structure, which stores urine. The urinary bladder is emptied by the process of micturition, i.e. the act of urination. Urethra This tube arises from the urinary bladder and helps to expel urine out of the body. In males, it acts as the common route for sperms and urine. Its opening is guarded by sphincter muscles. Q. Discuss structure and function of human excretory system. Answer:- the excretory system of humans removes nitrogenous waste products such as urea, small amount uric acids & other salts in form of urine. Excretory system is similar in both sexes and consists ofA pair of Kidneys A pair of ureters A urinary bladder An urethra A pair of kidneys External structure There are two dark red, bean shaped, metanephric kidneys attached to the dorsal wall of peritoneal cavity outs ide coelom. The right kidney is present a little behind the left one (due to presence of liver on right side). Each kidney is about 11X6X4 cm in size and enclosed in a capsule of connective tissue. It weighs 150gms in male and 135gms in female. The outer surface is convex & inner surface concave with a depression called hilus/hilum through which ureter arises. The ureters are narrow tubes which open into urinary bladder. Kidney get blood supply by a pair of renal arteries and purified blood drained away by a pair of renal veins. Each kidney bears a small triangular gland at top of each kidney called adrenal gland. Internal structure The L.S. of kidney has following structuresRenal capsule- I t is the thin envelop of kidney. Cortex- I t is the light red outer region of kidney. MedullaI t is dark reddish brown inner region with following partsPyramidsM edulla has several conical lobes with papilla called pyramids. Renal papilla- I t is the part of pyramid and projects towards the hilus . Renal column of Bertini - The cortex extended into medulla in between pyramids called renal columns of Bertini . Pelvis- The pyramids open inti small channels called calyces( major & miner) which collectively opens into pelvis of ureter . Miner calyces open into major calyx. The cortex & medulla contains more then 1 million coiled uriniferous tubules or nephrons in one kidney. These are the structural and functional unit of kidney. Histology The uriniferous tubules are bounded together by connective tissue, blood vessels, lymphatic vessels and nerves. The uriniferous tubules are joined with the collecting tubules which carry urine to the terminal duct of Bellini. I t opens into minor calyx at the apex of renal papilla which has 10-40 minute openings of ducts of Bellini. Structure of uriniferous tubule/Nephron According to position, nephrons are of two typesCortical nephron Juxta-medullary nephron . Cortical nephron Each uriniferous tubule has two partsNephron A collecting duct. Nephron it is about 35-50mm in length and 5060 m in diameter. It is formed of Malpighian corpuscles & renal tubules. Malpighian corpuscles- mostly present in cortex with following partsBowman’s capsule- it is a double walled cup like structure about 0.2mm in diameter. The outer wall is lined by squamous epithelial cells but inner wall is lined by podocytes ( flattened stellate cells). Glomerulus - it is the bunch of capillary formed by afferent renal arteriole. Blood from glomerulus passes out by efferent renal arteriole. It has also endothelium of glomerulus and Basement membrane. Renal tubuleIt is about 3.0cms long and 20-60 microns wide wit following regions. NeckIt is narrow part between Bowman’s capsule and PCT lined with ciliated epithelium. Proximal convoluted Tubule( PCT)it is about 14mm long and 60 m wide. The inner space is about 15-25 m wide. It is a much coiled structure. It is lined with cuboidal epithelial cell with free villi . These cells absorb about 2/3 of water of glomerular filtrate, all glucose and and a part of NaCl and PO 4 . PCT can be devided into two parts- pars convoluta ( present in cortex) and pars recta(straight tubule run towards medulla and joins with descending limb). Descending Limb- It enters into medulla & more permeable to H 2 O than solutes. Loop of Henle :It is narrow ‘U’ shaped loop between ascending and descending limb and present in medulla. Ascending limb :It is narrow, thin walled and joins with distal convoluted tubule. Distal convoluted tubule :Its length is 4.6 -5.2mm and diameter of about 20 – 50 m and lined with cubical cells. Collecting duct :- the DCT join with collecting duct. It is 20mm long. Several collecting tubules join to form duct of Bellini. It excretes nitrogenous and sulphur waste products and maintains osmoregulation . It maintains salt water balance, OP, BP, regulates erythropoiesis and preparation of vitamin D. Ureter A pair of thin muscular tubes called the ureter (30-35cm long) comes out of each kidney extending from the renal pelvis. It carries urine from the kidney to the urinary bladder. Urinary Bladder It is a muscular sac-like structure, which stores urine ( capacity 120ml to 320ml). The urinary bladder is emptied by the process of micturition. Urethra This tube arises from the urinary bladder and helps to expel urine out of the body. In males, it acts as the common route for sperms and urine. Its opening is guarded by sphincter muscles. It is about 18 to 20 cm long in male but 4cm in female. Q. Describe Ornithine cycle or Urea cycle. Answer:- Urea is synthesized by ornithine cycle in liver in ureotelic animals. During the process ammonia, CO2, ATP and aspartic acids are consumed. It was described by Hans Krebs and K. Hanseleit in 1932. Formation of urea occurs in two steps:Deamination of aminoacids Synthesis of urea in ornithine cycle. Deamination of aminoacids O2 is released in Photosynthesis. It supplies vast source of energy to man as fuel such as coal, oil, & wood. All living organisms get energy (Food) directly or indirectly by Photosynthesis. Photosynthesis maintains concentration of CO 2 &O 2 in atmosphere. The useful plant products like fodder, fire wood, timber, resin, gums, rubber etc are indirect product of photosynthesis. Mechanism of Photosynthesis: Light phase Dark Phase Q. what is Photosynthesis? Discuss the mechanism of light phase of Photosynthesis. Absorption of light energy by chloroplast pigments : Chlorophyll- Green pigments and of two types in higher plants such as Carotene – C 40 H 56 – Orange color Xanthophylls – C 40 H 56 O 2 – Yellow color Other pigments – Phycobillin , Phycoerythrin , Phycocyanin etc. These pigments absorb different wave length of light. Example: Chlorophyll a – Blue light Chlorophyll b – Red light Carotene – Blue and Yellow light Xanthophyll – Yellow light Transport of light energy to the reaction center from accessory pigments. PSI or Pigment system I – Its Photocenter is P 700 PSII or Pigment system II – Its Photocenter is P 680 Activation of Chlorophyll a molecule by photons of light. Electrone transport and photophosphorylation : Cyclic Photophosphorylation : Non-cyclic Photophosphorylation : 2H2O --------------------- 4H+ + 4e- + O2 Q. What is Photosynthesis? Discuss the Dark phase of Photosynthesis and write its significance. Answer: Definition: same as above with reaction. Dark phase: Dark phase is independent of light and also called biochemical pathway. It takes place in stroma region of chloroplast and depend on several enzymes. Dark phase is slower than light phase. In this phase CO2 is reduced to carbohydrates. Discovery of Calvin Cycle: This pathway was proposed by Malvin Calvin who got Nobel prize in1961. He experimented using radio isotop of Carbon (C14) in Chlorella (an unicellular alga) to trace the path of Carbon in Photosynthesis. This pathway operates in a cyclic manner and called Calvin cycle or C3 pathway. To synthesize on molecule of glucose Calvin cycle requires 6CO2, 18ATP and 12NADPH2. Mechanism: The Calvin cycle or C3 pathway has three steps. Carboxylative phase Reductive phase Regeneration Phase. A] Carboxylative Phase: 1. The first accepter of CO2 is Ribulose 1,5- biphosphate (5C) and first product is Phosphoglyceric acid(3C). Ribulose 1,5- biphosphate + CO2 -------------------------- 2 PGA (Phosphoglyceric acid) B] Reductive Phase: i) PGA + ATP + NADPH2 ------------------------------ Glyceraldehyde 3 P ii) Glyceraldehyde 3 P -------------------------------- Dihydroxy acetone 3 p. Glyceraldehyde 3P+ Dihydroxy acetone 3 p --------------------- Fructose-1.6 biphosphate . Fructose 1.6 biphosphate ----------------------- Fructose 6 P + H3PO4 Fructose 6 Phosphate is converted into fructose, glucose, sucrose and starch. C] Regenerative Phase: Ribulose 1.5 biphosphate is regenerated in following steps. Fructose 6 p + Gleceraldehyde 3p ----------------Xylulose 5P+ Erythrose 4P Erythrose 4P+ Dihydroxy acetone P ------------------------Sedoheptulose 1.7 diphosphate 4C 3C 7C Sedoheptulose 1.7 diphosphate -------------------------Sedoheptulose 7 P + H3PO4 Sedoheptulose 7P + Gleceraldehyde 3P --------------------Ribose 5P + Xylulose 5P Ribose 5P ---------------------Ribulose 5P Xylulose 5 P --------------------Ribulose 5P Ribulose 5 P + ATP ------------------------Ribulose 1.5biphosphate . Significance of Calvin Cycle: This cycle was first discovered to know the path of carbon in Photosynthesis. The living organisms depend on plants for food which produced through Calvin cycle. Various activities of plant and animal body directly or indirectly depend upon Calvin cycle. Q. What is Photosynthesis? Discuss C4 Pathway and write its significance. Answer: Definition: Same as above with equation. C4 Path way : Kortschak in 1954 reported in sugarcane that CO2 first enter into a 4 carbon compound called Oxaloacetic acid (OAA). Later Hatch & Slack reported it in maize and few grasses. As the first product of these plants is a 4 carbon compound, these plants are called C4 plants and the cycle of CO2 fixation called C4 Cycle. This is also called HSK path way after name of 3 scientists who reported it such as Hatch, Slack & Kortschak. AIR Mesophyll Cell Bundle Sheath Cell Vascular Bundle Aspertic Acid Calvin Cycle Oxaloacetic Acid CO2 PEP CO2 Malic Acid Sugar ATP Malic Acid Pyruvic Acid Pyruvic Acid Fig. : C4 Pathway Kranz Anatomy The C4 plants have peculiar leaf anatomy called Kranz anatomy. The vascular bundles are surrounded by Bundle sheath of Parenchyma cells which in turn surrounded by mesophyll cells. These cells bear two types of chloroplasts. Mesophyll Cells :Smaller chloroplast with grana . Bundle sheath Cells :Larger chloroplast without grana . Mechanism The mechanism involves the pathways taking place in Mesophyll Cells & in Bundle Sheath Cells. Reaction in Mesophyll Cells. CO 2 enters into leaf and first combines with Phosphoenol Pyruvic Acid (PEP) to form 4 carbon organic acid such as Oxaloacetic Acid (OAA) in presence of enzyme PEPCO ( PEP Carboxylase ). OAA reduced to Malic acid and also some aspartic Acid. Reaction in Bundle Sheath Cells . Malic Acid transfer to Bundle Sheath Cells through Plasmodesmata. Malic Acid dissociates into Pyruvic Acid & CO2. Malic Acid + NADP -------------------------------- Pyruvic Acid + NADPH + CO2 This CO2 enters into C3 Cycle or Calvin Cycle. Reaction in Mesophyll Cell . C4 Pathway developed as alternate pathway forCO 2 fixation. These plants are more efficient in CO 2 fixation then C 3 plants. XXX Difference between: C3 PLANTS C4 PLANTS Carbon Pathway is Calvin Cycle. Carbon Pathway is HSK Pathway. Primary acceptor of CO Primary acceptor of CO 2 is 2 is PEP. Ribulose The enzyme for 1 carboxylation ,5 is PEPCO The first product of biphosphate photosynthsis . is The enzyme for Oxaloacetic carboxylation acid (OAA). is RUBISCO. These have The first product of photosynthesis is Kranz phosphoglyceric anatomy. acid (PGA). These have two types of chloroplasts. These have normal anatomy in leaves. No photorespi These have only one type of chloroplast. ration occurs. Photorespiration occurs. Photosynthetically Photosynthetically more efficient. less efficient Ex- Sugarcane, Maize, Amaranthus and tropical grasses etc. Ex- Wheat, Rice , Cotton, Beans, sunflower etc. Photorespiration: Photorespiration is also called Glycolate metabolism or C 2 Cycle. It occurs in green cells of C 3 plants that contain Chloroplast, Mitochondria and Peroxisome . Under bright light & high temperature the enzyme Rubisco acts as Rubp oxygenase that accept O 2 to form 1 molecule of Phosphoglyceric acid and phosphoglycolic acid. Phosphoglycolic acid through Peroxisome and Mitochondria get oxidized to release CO 2 , It is a wasteful process in which about 50% of photosynthetic product is oxidized without release of energy. CHLOROPLAST PEROXISOME MITOCHONDRIA Glycolic acid Glycine Glycine Phosphoglyceric acid Calvin Cycle CO2 ATP NH3 Hydroxy Pyruvic acid Serine Glyceric acid Difference between: PHOTORESPIRATION DARK RESPIRATION Oxidation takes place by help of light. This process is independent of light. It occurs in cell containing chloroplast, Mitochondria and It occurs in cytoplasm and mitochondria. peroxisome It is a continuous process in which stored food . like glucose is oxidized. 50% of photosynthetic product is oxidized. Energy is released Energy is not released. It is an essential process. It is a wasteful process. CAM PLANTS: [Crassulacean acid metabolism plants] It is a special type of metabolism seen in some succulents (Fleshy xerophytes). These plants have both PEPCO and Rubisco enzymes. During night stomata open, CO 2 enters into the leaf and produces large amount of organic acids ( Oxaloacetic acid and malic acid). During day time these organic acid are decarboxylated to form CO 2 and Pyruvic acid. This CO 2 enters into Calvin Cycle and produce sugar. Blackman’s Law of Limiting Factor:F.F. Blackman 1905 formulated this law which was based on law of minimum by Lebig . This law is defined as when a process is conditioned as to its rapidity by a number of separate factors, the rate of the process become limited by the pace of the slowest factor. CO 2 , Temperature, Light may be the limiting factor as in the figure. Optimum Minimum Maximum Rate of Photosynthesis Temperature - Rate of Photosynthesis Light Intensity The external morphology of a frog includes: Body : Frogs have a stout body that's divided into a head and trunk, with no neck or tail. Skin : Frogs have smooth, moist, and slippery skin that's highly permeable and glandular. The skin can be brown, green, or vivid colors, and it absorbs water and helps frogs breathe. Eyes : Frogs have large, protruding eyes with a nictitating membrane that protects their eyes when they're in water. Ears : Frogs have a membranous tympanum, or ear, on the sides of their eyes that receives sound signals. Limbs : Frogs have strong, webbed hind feet and two forelimbs. They use their limbs to walk, swim, leap, and burrow. Nostrils : Frogs have a pair of nostrils. Vocal sacs : Male frogs have vocal sacs under their head. Copulatory pad : Male frogs have a copulatory pad on their forelimbs. Cloacal opening : Frogs have a cloacal opening at the posterior end of their trunk. Frogs are unisexual, meaning they exhibit sexual dimorphism. Size. Rana tigrina measures 12-20 cm in length. Shape. Roughly it is on triangular plane and adapted for swimming. Texture. Skin is smooth, moist and slippery. Colouration. The dorsal skin is green or olive coloured with dark patches, while ventral is whitish. Symmetry. It is bilaterally symmetrical. Division. Body is divided into two regions head and trunk. Neck and tail are absent. (a) Head It is conical and having blunt snout. Head has following parts : (i) External nares. These are two small openings lying near the anterior tip of snout. (ii) Eyes. They are the most distinct part of the head. Each eye is large, bright, protuberant, having golden iris and black rounded pupil. Each eye has an upper large and stationary eyelid.and a lower small mobile eyelid. (iii) Nictitating membrane. The upper part of lower eyelid forms a transparent nictitating membrane. (iv) Tympanum or tympanic membrane. It is in the form of a circular area found posterior to each eye. It forms external boundary of the middle ear. The external ear is absent in frog. (b) Trunk. It forms major portion of the body. It has characteristics raised hump. Trunk contains anterior forelimbs and posterior hindlimbs. (i) Forelimbs. Each comprises of upper arm, forearm and hand containing wrist, palm and four digits provided with copulatory or articular pads on inner finger of each hand in male frog. It helps in copulation. (ii) Hindlimbs. These are folded at rest and each. comprises of thigh, shank and foot. Foot is made up of ankle, sole and five digits. The web is present among toes which helps in swimming. (iii) Middorsal lines. There is a median longitudinal dorsal line surrounded by number of folds cailed plicae. (iv) Cloacal aperture. It lies at posterior end of trunk between two hind limbs. Respiratory system of Frog The respiratory system of a frog includes the following: Skin Frogs breathe through their skin, which is permeable to gases and has a rich blood supply. This is called cutaneous respiration. Lungs Frogs breathe through their lungs on land. Buccal cavity Frogs use their buccal cavity to breathe. To breathe in, a frog lowers the floor of its mouth, which expands the neck and nostrils. The air then enters the mouth, and when the nostrils close, the air is forced into the lungs. To breathe out, the frog lowers the floor of its mouth again, which sucks air out of the lungs and into the mouth. Gills Tadpoles and larvae use external gills to breathe, which is called branchial respiration. Frogs can breathe in a variety of ways, depending on whether they are on land or in water: On land : Frogs breathe through their lungs, buccal cavity, and skin. In water : Frogs breathe through their skin, which acts as an aquatic respiratory organ. Blood Vascular System of Frog The circulatory system of a frog is very well developed. In fact, just like humans, frogs also have a lymphatic system. A closed circulatory system is seen in frogs. The different organs present in this organ system are the heart, blood vessels, and blood. Lymph, lymph nodes and channels make up the lymphatic system. The heart has three chambers and is made up of muscle tissue. It is present in the upper part of the body. The three chambers of the heart consist of two atria and one ventricle. The pericardium covers the heart. Blood is opaque and sticky and is red in color due to the presence of haemoglobin. It has the blood cells and plasma. From the heart, the blood goes to all part of the body the arteries, which makes up the arterial system. The venous system comprising of all the veins carries blood from all organs to the heart. In frogs, there is also a hepatic portal system and renal portal system, where there is a venous connection present in the organs of liver, intestine, and kidneys.