HESI A2
HESI A2 Practice Test Biology
1. How are lipids different from other organic molecules?
- A. They are indivisible.
 - B. They are not water soluble.
 - C. They contain zinc.
 - D. They form long proteins.
 
Correct answer: B
Rationale: The correct answer is B: 'They are not water soluble.' Lipids are not water-soluble, which distinguishes them from other organic molecules. Choice A is incorrect because lipids are not indivisible; they can be broken down into fatty acids and glycerol. Choice C is incorrect as lipids do not necessarily contain zinc; they are a diverse group of molecules. Choice D is incorrect because lipids do not form long proteins; proteins are made up of amino acids, not lipids.
2. What are saturated fats saturated with?
- A. Hydrogen atoms
 - B. Carbon atoms
 - C. Oxygen atoms
 - D. Nitrogen atoms
 
Correct answer: A
Rationale: Saturated fats are saturated with hydrogen atoms. This means that each carbon atom in the fatty acid chains forming saturated fats is bonded to as many hydrogen atoms as possible. This saturation results in the fatty acid chains being straight and closely packed together, making saturated fats solid at room temperature. Choice B (Carbon atoms), C (Oxygen atoms), and D (Nitrogen atoms) are incorrect because saturated fats are specifically saturated with hydrogen atoms, not carbon, oxygen, or nitrogen atoms.
3. As cattle graze, cattle egrets consume the insects they stir up. This is an example of ___________.
- A. Mutualism
 - B. Parasitism
 - C. Commensalism
 - D. Competition
 
Correct answer: C
Rationale: Commensalism is a relationship between two species in which one benefits without affecting the other species. In this scenario, the cattle egrets benefit from the insects stirred up by cattle while the cattle are not significantly impacted by the presence of the egrets. The egrets obtain food easily, and the cattle are neither harmed nor helped by the egrets' presence, making it an example of commensalism. Mutualism involves both species benefiting, parasitism involves one species benefiting at the expense of the other, and competition involves both species being negatively affected by their interactions, none of which apply to the relationship between cattle and cattle egrets in this context.
4. What is the magnification of an ocular lens on a microscope?
- A. 4x
 - B. 10x
 - C. 40x
 - D. 100x
 
Correct answer: B
Rationale: The magnification of an ocular lens on a microscope is typically 10x, which is considered standard for most microscopes. Ocular lenses are designed to magnify the image produced by the objective lens further. Choices A, C, and D are incorrect because they do not represent the standard magnification of an ocular lens. A magnification of 4x, 40x, or 100x would not be typical for an ocular lens in a microscope.
5. Why do we perceive chlorophyll as green?
- A. It absorbs yellow and blue light.
 - B. It primarily absorbs green light.
 - C. It fails to absorb green light.
 - D. It primarily absorbs red light.
 
Correct answer: A
Rationale: Chlorophyll appears green to us because it primarily absorbs yellow and blue light while reflecting green light. The wavelengths of yellow and blue light are absorbed by chlorophyll for photosynthesis, which results in the green color we perceive. Choice B is incorrect because chlorophyll absorbs yellow and blue light, not green light. Choice C is incorrect because chlorophyll does absorb green light, but it also absorbs other wavelengths, primarily yellow and blue. Choice D is incorrect because chlorophyll primarily absorbs yellow and blue light, not red light.
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