OAT Biology 4

Question 1

Which blood vessel type has the thinnest walls, facilitating gas and nutrient exchange?

Accepted Answer

Capillaries

Answer

Capillaries have walls only one cell thick (endothelium), allowing efficient diffusion of gases and nutrients.

Question 2

The process by which a cell engulfs large solid particles is called:

Accepted Answer

Phagocytosis

Answer

Phagocytosis ('cell eating') involves pseudopod extension to engulf large particles such as bacteria or debris.

Question 3

Which nitrogenous base is found in RNA but NOT in DNA?

Accepted Answer

Uracil

Answer

RNA contains uracil in place of the thymine found in DNA; uracil pairs with adenine.

Question 4

In the human excretory system, the loop of Henle is critical for:

Accepted Answer

Creating a concentration gradient in the medulla

Answer

The loop of Henle establishes an osmotic gradient in the renal medulla that allows the collecting duct to concentrate urine.

Question 5

Which of the following best describes an exergonic reaction?

Accepted Answer

Releases net free energy and is thermodynamically spontaneous

Answer

Exergonic reactions have a negative ΔG, meaning they release free energy and occur spontaneously.

OAT - Optometry Admission Test Practice Test