Question 1

Which of the following best explains why small organisms, such as bacteria and hydra, can rely on direct diffusion for gas exchange?

Accepted Answer

They have a large surface area to volume ratio, allowing efficient exchange of gases across their body surface.

Question 2

A cube with a side length of 1 cm has a surface area to volume ratio of 6:1. If the side length increases to 3 cm, what happens to the surface area to volume ratio, and why is this significant for biological exchange?

Accepted Answer

The ratio decreases to 2:1, making exchange less efficient for larger organisms.

Question 3

Which of the following is a key structural adaptation in capillaries that maximizes their function in gas, nutrient, and waste exchange?

Accepted Answer

Microscopic diameter and single layer of endothelial cells.

Question 4

In mammals, which blood vessel carries oxygenated blood away from the heart to the body, and what is the significance of its structure?

Accepted Answer

Aorta; its thick, elastic walls withstand high pressure.

Question 5

Which equation best describes the relationship between pressure and volume in the thoracic cavity during inhalation, according to Boyle’s Law?

Accepted Answer

$$P 	imes V = k$$

Question 6

During exercise, the partial pressure of oxygen ($$PPO_2) in $$tissues decreases. What effect does this have on hemoglobin’s oxygen saturation and why?

Accepted Answer

Hemoglobin’s oxygen saturation decreases because more oxygen is unloaded to the tissues.

Question 7

Which of the following is true about the pulmonary circuit in mammals?

Accepted Answer

Pulmonary arteries carry deoxygenated blood to the lungs.

Question 8

A patient has a blood pressure reading of 150 mmHg over 95 mmHg. What condition does this indicate, and what risks are associated with it?

Accepted Answer

Hypertension; risk of atherosclerosis, heart attack, and stroke.

Question 9

Which of the following best describes the Bohr shift in hemoglobin function?

Accepted Answer

Decreased pH (more acidic) causes hemoglobin to release oxygen more readily.

Question 10

Which of the following is a function of precapillary sphincters in the circulatory system?

Accepted Answer

They regulate blood flow into capillary beds based on tissue needs.

Question 11

Which of the following statements about open and closed circulatory systems is correct?

Accepted Answer

Closed circulatory systems possess capillaries for exchange.

Question 12

What is the primary reason that veins have valves, while arteries do not?

Accepted Answer

Valves in veins prevent backflow due to low pressure and aid unidirectional flow toward the heart.

Question 13

Which of the following best describes the role of surfactant in the alveoli of the lungs?

Accepted Answer

Surfactant decreases surface tension, preventing alveolar collapse during exhalation.

Question 14

Which equation represents the conversion of carbon dioxide to bicarbonate in red blood cells, catalyzed by carbonic anhydrase?

Accepted Answer

$$CO_2 + H_2O$$ \rightarrow H_2CO_3 \rightarrow H^+ + $$HCO_3$$^-$$

Question 15

Which of the following is a consequence of atherosclerosis in arteries?

Accepted Answer

Formation of plaques that narrow the lumen and increase risk of heart attack or stroke.

Question 16

Which of the following best describes the function of hemolymph in organisms with open circulatory systems?

Accepted Answer

Hemolymph bathes organs directly in a hemocoel, transporting nutrients and gases.

Question 17

Which of the following is true regarding the direction of blood flow in the systemic circuit?

Accepted Answer

Blood flows from aorta to arteries to arterioles to capillaries to venules to veins to vena cava.

Question 18

Which of the following is a major function of blood plasma?

Accepted Answer

Transport of nutrients, wastes, hormones, and ions.

Question 19

Which of the following best explains why amphibians rely on their skin for gas exchange?

Accepted Answer

Their lungs have a small surface area, so their moist, highly vasculated skin provides a larger area for gas exchange.

Circulation and Gas Exchange: Structure and Function of Circulatory and Respiratory Systems

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