Question

Q.The cells lining the proximal convoluted tubule have numerous microvilli and mitochondria.  What is the implication of the presence of such structures and organelles?

a. Rapid osmosis occurs in the proximal convoluted tubule.

b. Energy-dependent active transport occurs in the proximal convoluted tubule.

c. The proximal convoluted tubule is the site of water conservation.

d. The proximal convoluted tubule is important in the storage of salts.

e. The production of urea requires a large amount of ATP.

Q. Which part of the kidney is the major site of glucose, amino acids, and vitamins resorption?

a. Bowman’s capsule.

b. The vasa recta.

c. The distal convoluted tubule.

d. The loop of Henle.

e. The proximal convoluted tubule.

Q. Two brine-filled compartments are separated by a water-permeable membrane (similar to the dialysis tubing we used in the laboratory).  The solution in compartment A has a higher osmotic pressure than compartment B.  This means that:

a. water will move from compartment B to compartment A.

b. water will move from compartment A to compartment B.

c. compartment A has a higher volume than compartment B.

d. the molecules in compartment A are larger than those in compartment B.

Answer 1

Q1. Energy dependent active transport occurs in the proximal convoluted tubule.

The proximal convoluted tubule is used for selective reabsorption of glucose, water, peptides and other tubular fluid nutrients back into the bloodstream. To ensure optimum surface area for reabsorption the cells lining this tubule are ciliated. One hand of the cell's membrane faces the tubule, and another faces the bloodstream. Sodium is pumped out into the bloodstream by active sodium / potassium pumps within the cell. This resulting lack of sodium induces a gradient of diffusion within the cell. Sodium within the tubule fluid will diffuse along this gradient into the cell, acting as a cotransporter for other important molecules such as glucose or water. Along with sodium, these molecules are carried into the cell. When inside, sodium is pumped out, while glucose and water, along their gradients, flow into the blood. Selective reabsorption ensures that essential molecules such as water and respiratory glucose are stored instead of excreted for immediate storage or use.

Q2. The proximal convoluted tubule.

Q3. water will move from compartment B to compartment A.

Osmosis is the movement of a solvent through a semipermeable membrane to a higher solute concentration (lower solvent concentration)