HESI A2
HESI A2 Biology 2024
1. Which structure might be described as a core of nucleic acid surrounded by a protein coat?
- A. RNA
- B. Virus
- C. Blue-green alga
- D. Saprophyte
Correct answer: B
Rationale: A virus can be described as a core of nucleic acid (either RNA or DNA) surrounded by a protein coat, known as a capsid. This structure distinguishes viruses from other microorganisms such as blue-green algae (Cyanobacteria), fungi known as saprophytes, or individual RNA molecules. Viruses depend on a host cell to replicate and are considered non-living entities due to their inability to carry out metabolic functions independently.
2. Which color of light is least effective at driving photosynthesis?
- A. Violet
- B. Green
- C. Orange
- D. Red
Correct answer: B
Rationale: Green light is the least effective at driving photosynthesis because chlorophyll, the primary pigment responsible for absorbing light in plants, does not absorb green light well. Instead, chlorophyll absorbs more effectively in the blue and red regions of the light spectrum. Therefore, green light is relatively less efficient in promoting photosynthesis compared to violet, orange, and red light. Violet light, although at the shorter wavelength end of the spectrum, can still drive photosynthesis better than green light. Orange and red light are more efficiently absorbed by chlorophyll, making them more effective in driving the process of photosynthesis.
3. Which cellular structure is found in animal cells but not in plant cells?
- A. Centriole
- B. Cytoplasm
- C. Vacuole
- D. Golgi apparatus
Correct answer: A
Rationale: The correct answer is A, Centriole. Centrioles are found in animal cells but not in plant cells. They play a crucial role in organizing microtubules during cell division, aiding in the formation of the mitotic spindle. Plant cells lack centrioles; instead, they utilize microtubule organizing centers to perform similar functions during cell division. Choices B, C, and D are incorrect because cytoplasm is a part of both animal and plant cells, vacuoles are found in plant cells and some animal cells, and the Golgi apparatus is present in both types of cells.
4. Tonicity refers to the movement of:
- A. Water
- B. Solute
- C. Cells
- D. None of the above
Correct answer: A
Rationale: Tonicity refers to the movement of water across a membrane in response to differences in solute concentration. In a hypertonic solution, where there is a higher concentration of solutes outside the cell, water will move out of the cell to try to reach equilibrium. In a hypotonic solution, where there is a lower concentration of solutes outside the cell, water will move into the cell to balance the concentrations. Cells and solutes themselves do not actively move in response to tonicity; it is the movement of water that helps achieve equilibrium. Therefore, the correct answer is water (Choice A). Choices B, C, and D are incorrect as tonicity specifically refers to water movement and not the movement of solutes, cells, or none of the above.
5. The apical side of an epithelial cell:
- A. Is exposed to fluid or air
- B. Is on the bottom side of the cell
- C. Does not allow any substances to pass through
- D. None of the above
Correct answer: A
Rationale: The apical side of an epithelial cell is the top side, which is typically exposed to fluids, air, or the inside of an organ. This side allows substances to pass through it, facilitating the absorption, secretion, or excretion of various substances. Choice B is incorrect as the apical side is not on the bottom but the top side. Choice C is incorrect as the apical side does allow substances to pass through. Choice D is incorrect as there are characteristics associated with the apical side.
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