Excretory Products and their Elimination Test 7

Correct Option: B

Explanation:

• “Active Transport is defined as a process that involves the movement of molecules from a region of lower concentration to a region of higher concentration against a gradient or an obstacle with the use of external energy.” -NCERT
• Example: The absorption of glucose in the human gut, as well as the uptake of minerals or ions into plant root hair cells, are both instances of active transport.

Hence, active transport is the process wherein molecules (ions, compounds etc.) travel from a region of their lower concentration to the region of their higher concentration (i.e., against the gradient using ATP) using energy.

 

 

The water and salts that are forced out of the glomerular capillaries, pass into the Bowman's capsule and is called the glomerular filtrate. The total filtrate passed out of the glomerulus in a normal kidney is about 170-180 liters per day.

The diameter of the afferent (incoming) arteriole is greater than the diameter of the efferent arteriole (by which blood leaves the glomerulus). The pressure of the blood inside the glomerulus is increased due to the difference in diameter of the incoming and outgoing arterioles. This increased blood pressure helps to force the components of the blood out of the glomerular capillaries. If the diameter of efferent arteriole becomes greater than the afferent arteriole, the process of glomerular filtration is hampered and it becomes very slow. The filtration of all the components is also not possible without the actual pressure gradient. 

Correct Option: D

Explanation:

• Osmoregulators use physiological mechanisms to maintain a more or less constant internal osmolarity.
• Terrestrial animals must osmoregulate since evaporation and excretion are unavoidable sources of water loss, and replacement water is not always readily accessible.

Hence, the terrestrial animals must conserve water in order to maintain the osmolarity of their body fluids.

Urea is the major excretory product. Its accumulation may cause toxicity so it needs to be thrown out of the body by deamination. Deamination is the removal of an amine group from a molecule. Enzymes that catalyse this reaction are called deaminases. In the human body, deamination takes place in the liver. The amino group is removed from the amino acid and converted to ammonia. Ammonia is toxic to the human system and enzymes convert it to urea or uric acid by addition of carbon dioxide molecules in the urea cycle, which also takes place in the liver. Urea and uric acid is excreted in urine.

The urea cycle converts two amino groups, one from ammonium ion and one from aspartate, and a carbon atom from bicarbonate, to the relatively nontoxic excretion product urea. Ornithine is the carrier of these carbon and nitrogen atoms. Glucose is completely reabsorbed by the capillaries. Thus, urea is finally the main product of urine.

The thick ascending limb is the more distal portion of the ascending limb of the loop of Henle, which continues as the last coiled segment of the renal tubule known as distal convoluted tubule (DCT). 

The glomerular filtrate contains all the materials present in the blood except blood cells and most proteins, which are too large to cross the basement membrane of the glomerulus. Hence, the filtrate is isotonic to blood plasma in the proximal convoluted tubule. 

• Generally, the urine of a man under normal conditions does not contain] any glucose because the kidneys are able to reabsorb all of the filtered glucose from the tubular fluid back into the bloodstream. 
• The glomerulus filters blood and produces the glomerular filtrate. This filtrate contains water, glucose, salts and urea. Large molecules such as protein are too large to fit through the blood capillary walls.
• The bowman's capsule collects the filtrate and enters the tubules. 
• All glucose is reabsorbed immediately into the blood capillaries. As the rest of the filtrate travels through the tubules water and salts needed by the body are reabsorbed into the blood capillaries.

Ureotelism is defined as the elimination of nitrogen mainly as urea. Aquatic mammals like whales and seals are said to be ureotelic animals because their major nitrogenous waste product is urea. As a matter of fact, ammonia is the basic nitrogenous metabolite of protein but since ammonia is highly toxic to the animals, therefore, its concentration must be kept very low in the blood and requires a large amount of water to be eliminated. So, the correct answer is 'If both the assertion and the reason are true and the reason is a correct explanation of the assertion'