Which of the following enzymes functions at the lowest pH?
Trypsin
Pancreatic amylase
Pepsin
Salivary amylase
The Correct Answer is C
A. Trypsin functions in the small intestine, where the environment is slightly alkaline. Therefore, this enzyme does not function at a low pH.
B. Pancreatic amylase also functions in the small intestine, where the pH is neutral to slightly alkaline.
C. Pepsin functions in the stomach, where the environment is highly acidic (pH 1.5 to 2). Pepsin is the correct answer because it works optimally at this low pH.
D. Salivary amylase functions in the mouth, where the pH is neutral or slightly alkaline.
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Correct Answer is A
Explanation
A. Diuretics increase urine output by inhibiting the reabsorption of water and sodium in the kidneys, which leads to increased water loss. This action is opposite to water conservation, making this the correct answer.
B. The counter current exchange system in the kidneys helps conserve water by maintaining a high osmolarity in the medulla, which facilitates the reabsorption of water in the collecting ducts. This system contributes to water conservation.
C. The collecting duct plays a crucial role in water reabsorption. Antidiuretic hormone (ADH) increases the permeability of the collecting duct to water, allowing more water to be reabsorbed back into the bloodstream, contributing to water conservation.
D. The counter current multiplier is a mechanism in the loop of Henle that creates a concentration gradient in the kidney medulla, which is essential for water reabsorption in the collecting ducts. It contributes to water conservation
Correct Answer is D
Explanation
A. Ca2+: prevents the entrance of any more sperm- While calcium ions play a role in the slow block to polyspermy, the fast block involves sodium ions.
B. Na+: prevents the entrance of more Na- The fast block to polyspermy involves sodium ions (Na+), but the depolarization of the egg membrane prevents the entrance of more sperm, not just more Na+.
C. Na+: prevents the entrance of Ca2+. The fast block prevents additional sperm from entering, not calcium ions.
D. Na+: prevents the entrance of any more sperm: The fast block to polyspermy involves the opening of sodium ion channels, leading to depolarization of the egg membrane. This depolarization prevents other sperm from binding to and penetrating the egg.