NEET AIPMT Biology Chapter Wise Solutions – Excretory Products and Their Elimination

NEET AIPMT Biology Chapter Wise Solutions – Excretory Products and Their Elimination

NEET AIPMT Biology Chapter Wise SolutionsPhysicsChemistry

1. Human urine is usually acidic because (AIPMT 2015)
(a) potassium and sodium exchange generates acidity
(b) hydrogen ions are actively secreted into the filtrate
(c) the sodium transporter exchanges one hydrogen ion for each sodium ion, in peritubular capillaries.
(d) excreted plasma proteins are acidic.

2. Which of the following does not favour the formation of large quantities of dilute urine? (AIPMT 2015, Cancelled)
(a) Renin
(b) Atrial-natriuretic factor
(c) Alcohol .
(d) Caffeine

3. Removal of proximal convoluted tubule from the nephron will result in (AIPMT2015, Cancelled)
(a) no change in quality and quantity of urine
(b) no urine formation
(c) more diluted urine
(d) more concentrated urine.

4. Which of the following causes an increase in sodium reabsorption in the distal convoluted tubule? (AIPMT 2014)
(a) Increase in aldosterone levels.
(b) Increase in antidiuretic hormone levels.
(c) Decrease in aldosterone levels.
(d) Decrease in antidiuretic hormone levels.

5. Select the option which shows correct matching of animal with its excretory organ and excretory product. Animal Excretory Excretoryorgan product (Karnataka NEET 2013)
(a) Labeo (Rohu) Nephridial tubes Ammonia
(b) Salamander Kidneys Urea
(c) Peacock Kidneys Urea
(d) Housefly Renal tubules Uric acid

6. The maximum amount of electrolytes and water (70 – 80 percent) from the glomerular filtrate is reabsorbed in which part of the nephron? (Prelims 2012)
(a) Ascending limb of loop of Henle
(b) Distal convoluted tubule
(c) Proximal convoluted tubule
(d) Descending limb of loop of Henle.

7. Which one of the following options gives the correct categorization of six animals according to the type of nitrogenous waste they give out?

8. A fall in glomerular filtration rate (GFR) activates (Mains 2012)
(a) juxtaglomerular cells to release renin
(b) adrenal cortex to release aldosterone
(c) adrenal medulla to release adrenaline
(d) posterior pituitary to release vasopressin.

9. Which one of the following characteristics is common both in humans and adult frogs? {Mains 2012)
(a) Four chambered heart
(b) Internal fertilization
(c) Nucleated RBCs
(d) Ureotelic mode of excretion.

10. Which one of the following is not a part of a renal pyramid? (Mains 2011)
(a) peritubular capillaries
(b) convoluted tubules
(c) collecting ducts
(d) loop of Henle

11. Which one of the following correctly explains the function of a specific part of the human nephron? (Mains 2011)
(a) podocytes : create minute spaces (slit pores) for the filtration of blood into the Bowman’s capsule
(b) Henle’s loop : most reabsorption of the major substances from the glomerular filtrate
(c) distal convoluted tubule : reabsorption of K⁺ ions into the surrounding blood capillaries
(d) afferent arteriole: carries the blood away from the glomerulus towards renal vein.

12. Which one of the following statements is correct with respect to kidney function regulation? (Mains 2011)
(a) when someone drinks lot of water, ADH release is suppressed
(b) exposure to cold temperature stimulates ADH release
(c) an increase in glomerular blood flow stimulates formation of angiotensin II
(d) during summer when body loses lot of water by evaporation, the release of ADH is suppressed.

13. Uricotelic mode of excreting nitrogenous wastes is found in (Mains 2011)
(a) reptiles and birds
(b) birds and annelids
(c) amphibians and reptiles
(d) insects and amphibians

14. Which one of the following statements in regard to the excretion by the human kidneys is correct? (Prelims 2010)
(a) descending limb of loop of Henle is impermeable to water
(b) distal convoluted tubule is incapable of reabsorbing HCO₃
(c) nearly 99 per cent of the glomerular filtrate is reabsorbed by the renal tubules
(d) ascending limb of loop of Henle is impermeable to electrolytes.

15. The principal nitrogenous excretory compound in humans is synthesised (Prelims 2010)
(a) in kidneys but eliminated mostly through liver
(b) in kidneys as well as eliminated by kidneys
(c) in liver and also eliminated by the same through bile
(d) in the liver, but eliminated mostly through kidneys.

16. What will happen if the stretch receptors of the urinary bladder wall are totally removed? (Prelims 2009)
(a) micturition will continue
(b) urine will continue to collect normally in the bladder
(c) there will be no micturition
(d) urine will not collect in the bladder

17. Uric acid is the chief nitrogenous component of the excretory products of (Prelims 2009)
(a) earthworm
(b) cockroach
(c) frog
(d) man

18. A person who is on a long hunger strike and is surviving only on water, will have (2007)
(a) less amino acids in his urine
(b) more glucose in his blood
(c) less urea in his urine
(d) more sodium in his urine.

19. Angiotensinogen is a protein produced and secreted by (2006)
(a) juxtaglomerular (JG) cells
(b) macula densa cells
(c) endothelial cells (cells lining the blood vessels)
(d) liver cells

20. In ornithine cycle, which of the following wastes are removed from the blood? (2005)
(a) CO₂ and urea
(b) ammonia and urea
(c) CO₂ and ammonia
(d) urea and urine.

21. The net pressure gradient that causes the fluid to filter out of the glomeruli into the capsule is (2005)
(a) 50 mm Hg
(b) 75 mm Hg
(c) 20 mm Hg
(d) 30 mm Hg.

22. A person is undergoing prolonged fasting. His urine will be found to contain abnormal quantities of (2005)
(a) fats
(b) amino acids
(c) glucose
(d) ketones.

23. If Henle’s loop were absent from mammalian nephron, which one of the following is to be expected ? (2003)
(a) there will be no urine formation
(b) there will be hardly any change in the quality and quantity of urine formed
(c) the urine will be more concentrated
(d) the urine will be more dilute

24. Conversion of ammonia to urea is done by (2000)
(a) ornithine cycle
(b) arginine cycle
(c) fumaric cycle
(d) citrulline cycle.

25. Concentration of urine depends upon which organ? (2000)
(a) Bowman’s capsule
(b) length of Henle’s loop
(c) P.C.T.
(d) network of capillaries arising from glomerulus.

26. A condition of failure of kidney to form urine is called (1998)
(a) anuria
(b) deamination
(c) uremia
(d) none of these.

27. The basic functional unit of human kidney is (1997)
(a) nephridia
(b) Henle’s loop
(c) nephron
(d) pyramid.

28. In ureotelic animals, urea is formed by (1997)
(a) Krebs cycle
(b) EM pathway
(c) Ornithine cycle
(d) Cori’s cycle.

29. The ornithine cycle removes two waste products from the blood in liver. These products are (1996)
(a) CO₂ and ammonia
(b) ammonia and uric acid
(c) CO₂ and urea
(d) ammonia and urea.

30. A red blood cell was kept in a solution for a few minutes, where it got burst. The solution taken was (1994)
(a) hypotonic
(b) concentrated sugar solution
(c) isotonic
(d) hypertonic.

31. Which one of the four parts mentioned below does not constitute a part of single uriniferous tubule? (1994)
(a) distal convoluted tubule
(b) collecting duct
(c) Bowman’s capsule
(d) loop of Henle.

32. If excess water passes out from the tissue without being restored by the kidneys, the cells would (1994)
(a) burst open and die
(b) take water from the plasma
(c) not be affected at all
(d) shrivel and die.

33. Glucose is taken back from glomerular filtrate through (1993)
(a) active transport
(b) passive transport
(c) osmosis
(d) diffusion.

34. Nitrogenous waste products are eliminated mainly as (1991)
(a) urea in tadpole and ammonia in adult frog
(b) ammonia in tadpole and urea in adult frog
(c) urea in both tadpole and adult frog
(d) urea in tadpole and uric acid in adult frog.

35. Under normal conditions which one is completely reabsorbed in the renal tubule? (1991)
(a) urea
(b) uric acid
(c) salts
(d) glucose.

36. Proximal and distal convoluted tubules are parts of (1990)
(a) seminiferous tubules
(b) nephron
(c) oviduct
(d) vas deferens.

37. Brush border is characteristic of (1990)
(a) neck of nephron
(b) collecting tube
(c) proximal convoluted tubule
(d) all of the above.

38. Reabsorption of useful substances from glomerular filtrate occurs in (1989)
(a) collecting tube
(b) loop of Henle
(c) proximal convoluted tubule
(d) distal convoluted tubule.

EXPLANATIONS

1. (b)

2. (a)
Angiotensinogen is an a-globulin protein produced by liver. Renin serves as an enzyme in the conversion of the plasma protein angiotensinogen into angiotensin. This protein stimulates the adrenal cortex to produce aldosterone which acts on the cells of the ascending limb of the loop of Henle, and increases the rate of reabsorption of Naf Reabsorption of Na⁺ brings about the uptake of an osmotically equivalent amount of water. Absorption of sodium and water increases blood volume and pressure.

3. (d)
About 65% of the glomerular filtrate is normally reabsorbed in proximal convoluted tubule before reaching the loop of Henle. It absorbs glucose, amino acids, vitamins, hormones, Na, K, Cl, phosphates, bicarbonates, water and urea etc. If it is removed, then more concentrated urine with high osmolarity will be produced.

4. (a)
Aldosterone is a hormone secreted by the outer layer of the adrenal gland (cortex part). Decreased blood volume and interstitial fluid level, resulting in decreased blood pressure, trigger aldosterone secretion. When aldosterone is present in the blood, reabsorption of Na⁺ in the filtrate is increased by the epithelial cells of the collecting duct. Retaining Na^–, raises the osmotic pressure of the blood and reduces water loss from the body. When aldosterone is absent, some Na- remains in the filtrate and is excreted with the urine.

5. (b)
In salamander, kidneys (mesonepheric) are the excretory organs and the excretory matter is urea. In Labeo, mesonephric kidney is the excretory organ and excretion is ammonotelic.
Peacock has metanephric kidneys with excretory matter being uric acid. In housefly, excretion takes place by Malpighian tubules. Excretory waste is uric acid chiefly.

6. (c)
During glomerular filtration in kidneys, ultrafiltration of blood occurs i.e., almost all the constituents of plasma except proteins pass onto the Bowman’s capsule. Then nearly 99% of the filtrate is reabsorbed by renal tubules. Proximal convoluted tubules shows maximum reabsorption and nearly all the essential nutrients and 70-80% of electrolytes and water are reabsorbed by this segment.

7. (c)

8. (a)
The amount of the filtrate formed by the kidneys per minute is called glomerular filtration rate (GFR). GFR in a healthy individual is approximately 125 ml/ minute, i.e., 180 litres per day.
The kidneys have built-in mechanisms for the regulation of glomerular filtration rate. One such efficient mechanism is carried out by juxtaglomerular apparatus (JGA). JGA is a special sensitive region formed by cellular modifications in the distal convoluted tubule and the afferent arteriole at the location of their contact. A fall in GFR can activate the JG cells to release renin which can stimulate the glomerular blood flow and thereby the GFR come back to normal.

9. (d)
Excretion of urea is known as ureotelism and the animals which excrete urea are called ureotelic. Ureotelic animals include Ascaris, earthworm (both are ammonotelic and ureotelic), cartilaginous fishes like sharks and sting rays, semi-aquatic amphibians such as frogs and toads, aquatic or semi- aquatic reptiles like turtles, terrapins and alligators, and man and all other mammals. Urea is less toxic and less soluble in water than ammonia. Hence, it can stay for some time in the body. Amphibian tadpole (e.g., tadpole of frog) excrete ammonia but after metamorphosis frog excretes urea.

10. (b)
The medulla of kidney is divided into a number of conical areas, the medulla pyramids or renal pyramids. Peritubular capillaries, loop ofHenle and collecting ducts lie in the medulla (renal pyramids) while convoluted tubules lie in the cortex of kidney.

11. (a)
The visceral layer of Bowman’s capsule surrounds the glomerulus and is composed of special type of cells, the podocytes. The podocytes are so called because they possess foot like processes (projection), the pedicels. The space between pedicels are called slit pores (= filtration slits) through which the glomerular filtrate filters.

12. (a)
Antidiuretic hormone (ADH) or Vasopressin increases the reabsorption of water in the distal convoluted tubule, collecting tubules and collecting ducts of the nephrons of the kidneys. As a result, the reabsorption of water from the glomerular filtrate is increased. When someone drinks lot of water, requirement of absorption of water decreases, so ADH release is suppressed.

13. (a)
Reptiles, birds, land snails and insects excrete nitrogenous wastes as uric acid in the form of pellet or paste with a minimum loss of water and are called uricotelic animals.

14. (c)
Urine formation involves three main processes namely, glomerular filtration, reabsorption and secretion, that takes place in different parts of the nephron. A comparison of the volume of the fdtrate formed per day (180 litres per day) with that of the urine released (1.5 litres), suggest that nearly 99 percent of the filtrate is reabsorbed by the renal tubules. The descending limb of loop of Henle is permeable to water but almost impermeable to electrolytes. The ascending limb is impermeable to water but allows transport of electrolytes actively or passively. Conditional reabsorption ofNa+ and water takes place in distal convoluted tubule. It is also capable of reabsorption of HCO₃.

15. (d)
The principle nitrogenous excretory compound in humans is urea. Urea is produced in a series of reactions (urea cycle) which take place in the mitochondrial matrix and cytosol of liver cells. Urea cycle (ornithine cycle) is the series of biochemical reactions that converts ammonia, which is highly toxic, and carbon dioxide to the much less toxic urea during the excretion of metabolic nitrogen derived from the deamination of excess amino acids. The urea is ultimately excreted in solution in urine.

16. (a)
Sensory stretch receptors are responsible for the stretch reflex. If these are removed then autonomic nervous system control will not be there and micturition will continue. Micturition is the expulsion of urine from the urinary bladder.

17. (b)
Cockroach shows uricotelism. Excretion of uric acid is known as uricotelism and the animals which excrete uric acid are called uricotelic. Animals which live in dry conditions have to conserve water in their bodies. Therefore, they synthesize crystals of uric acid from ammonia. Uric acid crystals are non-toxic and almost insoluble in water. Hence, these can be retained in the body for a considerable time. Uricotelic animals include most insects, (e.g., cockroach), land reptiles (e.g., lizards and snakes) and birds.

18. (c)
A person who is on a long hunger strike and is surviving only on water, will have less urea in his urine. Urea, also called carbamide, is an organic chemical compound which essentially is the waste produced when the body metabolizes protein. Manufactured in the liver, by broken down protein or amino acids, and ammonia, the kidneys transfer urea from the blood to the urine. The average person excretes about 30 grams of urea a day. During total starvation with no food being eaten, the body must rely on its own tissues to provide the essential mixture of fuels to sustain life. The primary fuel is stored fat but we also need a continuous supply of glucose. The body has a very small store of glycogen that can provide glucose for about 36 hours, then the body must make its glucose. The body has three sources of glucose, one is the diet (but the person is starving), a second is glycogen (but this is all gone) and the third is a process called gluconeogenesis where the body makes glucose from amino acids. During starvation, the body must rely on body proteins for the amino acids. On high-protein diets the carbon skeletons of the amino acids are oxidized for energy or stored as fat and glycogen, but the amino nitrogen must be excreted. To facilitate this process, enzymes of the urea cycle are controlled at the gene level. When dietary proteins increase significantly, enzyme concentrations rise. On return to a balanced diet, enzyme levels decline. Under conditions of starvation, enzyme levels rise as proteins are degraded and amino acid carbon skeletons are used to provide energy, thus increasing the quantity of nitrogen that must be excreted in the form of urea.

19. (d)
Angiotensinogen is an a-globulin protein produced by liver. Renin serves as an enzyme in the conversion of the plasma protein angiotensinogen into angiotensin. This protein stimulates the adrenal cortex to produce aldosterone which acts on the cells of the ascending limb of the loop of Henle, and increases the rate of reabsorption of Na^–. Reabsorption of  Na⁺ brings about the uptake of an osmotically equivalent amount of water. Absorption of sodium and water increases blood volume and pressure.

20. (c)
Refer answer 15.

21. (c)
Walls of glomerular capillaries and Bowman’s capsule are very thin and are semipermeable due to the presence of pores in the former and slit-pores in the latter. They allow water and small molecules in the blood to pass through them. Fluid containing these materials is forced out of the glomerular capillaries into the Bowman’s capsule by the high pressure of the blood in the glomerular capillaries. This pressure is about 70 mm. Hg in man. The fluid tends to move in the reverse direction due to (i) the osmotic pressure of plasma proteins in the glomerular capillaries, and (ii) hydrostatic pressure of the fluid in the urinary tubule. These pressures in man are about 30 mm. Hg. and 20 mm. Hg. respectively. The net force moving the fluid from the glomerular capillaries, called the filtration pressure, is 70-(30+ 20) or 20 mm. Hg.

22. (d)
Under fasting conditions which are associated with high rate of fatty acid oxidation, the liver produces large amount of ketone bodies viz. – acetoacetate, (3-hydroxybutyrate and acetone. The normal level of ketone blood level is 0.2 mmol/L. Presence of excess ketone bodies in urine is termed ketonuria.

23. (d)
Reabsorption is a process by which useful constituents of glomerular filtrate are returned into the blood streams. It occurs in convoluted tubules (proximal convoluted tubule) as well as loop of Henle. Basically loop of Henle, in association with vasa rectae, plays an important role in the counter current mechanism (the process which makes urine hypertonic, i.e., more concentrated).
Therefore if Henle’s loop was absent from mammalian nephron the urine will be more dilute.

24. (a)
Refer answer 15.

25. (b)
Concentration of urine depends upon the length of Henle’s loop. Loop of Henle is the hairpin shaped section of a kidney tubule situated between the proximal and distal tubules in the nephron. It consists of a thin descending limb which is permeable to water and a thick ascending limb which is impermeable to water complex movements of ions and water across the walls of the loop enable it to function as a countercurrent multiplier, resulting in the production of concentrated urine in the collecting duct.

26. (a)
Anuria is the complete suppression of urine formation by the kidney. In this case most of the nephrons are destroyed. Uremia is the presence of an excessive amount of urea in the blood. Deamination is the removal of ammonia from amino acids.

27. (c)
A nephron is a unit of structure and function in a kidney. A kidney contains about a million nephrons, each approximately 3 cm. long.
A nephron is a long tubule differentiated into four regions having different anatomical features and physiological role
Bowman’s capsule, proximal convoluted tubule (PCT), loop of Henle, and distal convoluted tubule (DCT). The latter opens into one of the collecting ducts. Nephridia are the excretory organs of annelids.

28. (c)
Refer answer 15.

29. (a)
Urea is formed of two molecules of ammonia and one molecule of CO₂
During catabolism, proteins break up into amino acids. The amino acids are converted into keto-acids (such as a- keto-glutaric acid) with the removal of ammonia (deamination). The keto-acid enters the Krebs cycle to yield energy. Carbon dioxide is formed during decarboxylation.
Ornithine (amino acid) combines with one molecule of NH₃ and CO₂ producing citrulline (amino acid) and water. Citrulline combines with another molecule of ammonia and forms arginine (essential amino acid) and water. Arginine is broken into urea and ornithine in the presence of an enzyme arginase and water. Thus the cycle is repeated. This is called urea or ornithine or Krebs- Henseleit cycle after the names of its discoverers.

Most of the urea is produced in the liver. The liver cells continuously release urea into the blood and kidneys withdraw it from the blood to excrete it in urine.

30. (a)
A cell gains water if it is kept in hypotonic solution or pure water. The phenomenon is called endosmosis. If the red blood cells are placed in a hypotonic solution, one in which the concentration of solutes is less and concentration of water is greater than inside the cells, they will take up water by endosmosis to equalize the water concentration, swell up and may burst. The swelling cells protoplast exerts pressure on the surrounding cell membrane or wall if present. It is called hydrostatic pressure or turgor pressure. Animal cells do not have a wall, therefore high turgor pressure causes their bursting.

31. (b)
Refer answer 27.

32. (c)
Individual cells have no role to play in this process. Excess water in the blood affects the osmoreceptors present in hypothalamus and volumereceptors present in left atrium, ventricles and pulmonary veins. This causes ADH release so that body hydration is regulated by removal of excess water by kidney.

33. (a)
Glucose is taken back from the glomerular filtrate by the proximal convoluted tubule by active transport.

34. (b)
Ammonia is highly soluble in water, so in aquatic animals e.g., tadpole of frog, the nitrogenous waste products are excreted in the form of ammonia. In terrestrial animals e.g., adult frog, these wastes are excreted in the form of urea.

35. (d)
The cells lining the proximal convoluted tubule are well adapted for reabsorption of materials from the filtrate. They have abundant mitochondria and bear numerous microvilli on the free side thus giving brush border appearance. The cells reabsorb entire glucose, amino acids, most of the inorganic ions, much of the water as well as some urea from the filtrate.

36. (b)
Refer answer 27.

37. (c)
The cells lining the proximal convoluted tubule are well adapted for reabsorption of materials from the filtrate. They have abundant mitochondria and bear numerous microvilli on the free side. Mitochondria power the active transport of nutrient molecules back into the blood. The cells reabsorb entire glucose, amino acids, most of the inorganic ions (Na^– k^– Cl^–) ,much of the water as well as some urea from the filtrate.

38. (c)
Refer answer 37.