HESI A2
HESI A2 Biology Practice Test
1. The procedure to focus an image using a compound microscope involves
- A. Adjusting the coarse adjustment each time a new magnification is selected
- B. Adjusting the fine adjustment each time a new magnification is selected
- C. Adjusting the stage each time a new magnification is selected
- D. All of the above
Correct answer: B
Rationale: When using a compound microscope, it is essential to adjust the fine adjustment knob each time you switch to a new magnification level. The fine adjustment knob allows for precise focusing on the specimen at different magnifications, ensuring a clear and sharp image. The coarse adjustment knob is typically used only at the lower magnification settings to bring the image into view roughly. Adjusting the stage may be necessary based on the size and thickness of the specimen, but it does not need to be done every time a new magnification is selected. Therefore, option B is the correct choice as it focuses on the key aspect of precise focusing during magnification changes.
2. Which one of the following best describes the function of a cell membrane?
- A. It controls the substances entering and leaving the cell.
- B. It maintains the cell's shape.
- C. It controls the substances entering the cell.
- D. It supports the cell's structures.
Correct answer: A
Rationale: The correct answer is A. The function of a cell membrane is to control the substances entering and leaving the cell. The cell membrane is selectively permeable, allowing it to regulate the movement of ions and molecules in and out of the cell to maintain internal balance and proper function. Choice B is incorrect because while the cell membrane does provide some structural support, its primary function is not to maintain the cell's shape. Choice C is incorrect because the cell membrane controls both the substances entering and leaving the cell, not just those entering. Choice D is incorrect as the primary function of the cell membrane is not to support the cell's structures but to regulate the movement of substances.
3. What is the binding membrane of an animal cell called?
- A. Biological membrane
- B. Cell coat
- C. Unit membrane
- D. Plasma membrane
Correct answer: D
Rationale: The correct answer is D: Plasma membrane. The plasma membrane surrounds the cell and acts as an interface between the living interior of the cell and the nonliving exterior. It plays a vital role in maintaining the cell's integrity, regulating the passage of substances in and out of the cell, and facilitating communication with other cells. Choices A, B, and C are incorrect because the term 'plasma membrane' specifically refers to the binding membrane of an animal cell, distinguishing it from other types of membranes or coatings found in cells.
4. During which phase of mitosis does the nuclear envelope disintegrate?
- A. Prophase
- B. Prophase
- C. Prometaphase
- D. Metaphase
Correct answer: C
Rationale: During the prometaphase stage of mitosis, the nuclear envelope disintegrates. This allows the condensed chromosomes to move towards the center of the cell, preparing for their alignment along the metaphase plate. The breakdown of the nuclear envelope is a crucial step in mitosis to ensure the proper segregation of genetic material into daughter cells. Choices A, B, and D are incorrect as the nuclear envelope disintegration specifically occurs during the prometaphase stage, not in prophase or metaphase.
5. Prokaryotic cells:
- A. Have a nucleus
- B. Have a capsule
- C. Have membrane-bound organelles
- D. Cannot move on their own
Correct answer: B
Rationale: Prokaryotic cells do not have a nucleus or membrane-bound organelles. One characteristic feature of prokaryotic cells is the presence of a capsule, which is a protective layer outside the cell wall. This capsule helps the prokaryotic cell adhere to surfaces, evade the host immune system, and protect against desiccation. Choice A is incorrect because prokaryotic cells lack a nucleus. Choice C is incorrect as prokaryotic cells do not have membrane-bound organelles. Choice D is incorrect as prokaryotic cells can move using structures like flagella or pili.
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