what is the primary function of the alveoli in the lungs

HESI A2

Anatomy HESI A2 Practice Test

1. What is the primary function of the alveoli in the lungs?

A. Removing carbon dioxide from the blood
B. Exchanging oxygen and carbon dioxide
C. Transporting oxygen to the bloodstream
D. Filtering blood

Correct answer: B

Rationale: The primary function of the alveoli in the lungs is to exchange oxygen and carbon dioxide. The alveoli are tiny air sacs in the lungs responsible for this gas exchange during breathing. Oxygen diffuses from the inhaled air into the blood in the capillaries surrounding the alveoli, while carbon dioxide diffuses from the blood into the alveoli to be exhaled out of the body. Choice A is incorrect because the alveoli primarily facilitate the exchange of gases, not just the removal of carbon dioxide. Choice C is incorrect as the alveoli do not transport oxygen to the bloodstream but rather facilitate the exchange of gases. Choice D is incorrect as the alveoli are not involved in filtering blood but in gas exchange to ensure proper oxygenation and removal of carbon dioxide in the respiratory process.

2. Which statement is true of enzymes?

A. They are made from lipids.
B. They are made from proteins.
C. They form double chains of DNA.
D. They bind with catalysts.

Correct answer: B

Rationale: The correct answer is B: Enzymes are made from proteins. Enzymes are biological molecules that act as catalysts to speed up chemical reactions in living organisms. While the majority of enzymes are proteins, a few are made from RNA. The statement that enzymes are made from lipids (choice A) is incorrect. Enzymes do not form double chains of DNA (choice C) as their primary function is not related to DNA structure. Additionally, enzymes themselves do not bind with catalysts (choice D); instead, they act as catalysts to facilitate reactions.

3. A key parameter in fluid selection is specific gravity (SG). For a submerged object in a reference fluid (often water), SG = ρ_object / ρ_reference. An object with SG > 1 will:

A. Experience a net buoyant force acting upwards
B. Experience a net buoyant force acting downwards
C. Remain neutrally buoyant
D. Require knowledge of the object's volume for buoyancy determination

Correct answer: A

Rationale: When the specific gravity (SG) of an object is greater than 1, it indicates that the object is denser than the reference fluid, which is often water. According to Archimedes' principle, an object with SG > 1 will experience a net buoyant force acting upwards when submerged in the fluid. This is because the buoyant force is greater than the weight of the object, causing it to float. Therefore, the correct answer is A: 'Experience a net buoyant force acting upwards.' Objects with SG < 1 would sink as they are less dense than the fluid, while objects with SG = 1 would be neutrally buoyant, neither sinking nor floating.

4. Why are bacteria and blue-green algae often classified together?

A. Both are gymnosperms.
B. Both are prokaryotes.
C. Both are autotrophs.
D. Both are pathogens.

Correct answer: B

Rationale: Bacteria and blue-green algae (cyanobacteria) are often classified together because they are both prokaryotes. Prokaryotes are unicellular organisms that lack a membrane-bound nucleus and other membrane-bound organelles. This characteristic distinguishes them from eukaryotic organisms, which have these membrane-bound structures. Choice A is incorrect because gymnosperms are seed-producing plants with naked seeds, not bacteria or blue-green algae. Choice C is incorrect because being an autotroph (able to produce its own food) is not a reason for classifying them together. Choice D is incorrect because not all bacteria and blue-green algae are pathogens; many of them are beneficial or neutral to other organisms.

5. Find x. 120:x = 40:0.5.

A. 60
B. 0
C. 1
D. 25

Correct answer: C

Rationale: To find x, set up the proportion and solve for x: 120/x = 40/0.5. Cross multiply to get 120 * 0.5 = 40x. This simplifies to 60 = 40x. Divide by 40 to isolate x, giving x = 60/40 = 1. Therefore, the correct answer is C, which is 1. Choice A (60) is incorrect because it does not match the correct calculation. Choice B (0) is incorrect as the calculation results in x = 1, not 0. Choice D (25) is incorrect as it does not match the correct calculation of x = 1.