FREE NEET Biology Practice MCQ Test: Excretory Products And Their Elimination Exercise 2 Questions Answers With Detailed Explanations [PDF]

Answer: (a)

Vasa recta are a series of straight capillaries in the medulla. They lie parallel to the loop of Henle.

Answer: (b)

Renin converts angiotensinogen in blood to angiotensin I and further to angiotensin II (a vasoconstrictor).

Answer: (a)

Answer: (c)

Answer: (d)

Ascending limb of Loop of Henle are thick walled and impermeable to water. Descending limb of loop of Henle is thin walled and permeable to water but impermeable to salt and thus indirectly contributes to the concentration of the interstitium. Distal convoluted tubule is a portion between the loop of Henle and the collecting duct system which is capable of reabsorption of $HCO_{3}^{–}$ and selective secretion of hydrogen and potassium ions and NH3 to maintain the pH and sodium-potassium balance in the blood.

Answer: (c)

Answer: (b)

Juxtaglomerular cells secrete an enzyme renin into blood. Renin changes plasma protein angiotensiongen to a peptide called angiostensin 11. It increases the blood volume : (i) by inducing proximal convoluted tubules to reabsorb more NaCl and water (ii) stimulates the adrenal glands to release a hormone called aldosterone which induces the distal convoluted tubule to absorb more $Na^{+}$ and water.

Answer: (c)

Answer: (d)

This is the correct flow of urine after it leaves the kidney.

Answer: (a)

Answer: (d)

In ureotelic animals, ammonia is converted into less toxic urea (for conservation of water).

Answer: (c)

Answer: (b)

Answer: (a)

Answer: (b)

Kangaroo rat lives in desert, therefore, it needs to conserve water in the body. In kangaroo rat, loop of Henle is significantly longer as it descends further into the medulla and produces a higher concentration gradient in the surrounding tissue so as to produce urine which is 18 times concentrated than that of their blood. This gradient allows more water to diffuse into the surrounding tissues to be reabsorbed.

Answer: (a)

Urea is formed of two molecules of ammonia and one molecule of $CO_2$. During catabolism, proteins break up into amino acids. The amino acids are converted into keto-acids (such as α-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 $NH_3$ and $CO_2$ 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.

Answer: (d)

Answer: (c)

Answer: (a)

Answer: (a)