HESI A2
HESI A2 Biology 2024
1. Which organelle provides storage space for the cell?
- A. Mitochondrion
- B. Vacuole
- C. Cell membrane
- D. Ribosome
Correct answer: B
Rationale: The correct answer is B: Vacuole. The vacuole is the organelle responsible for providing storage space in the cell. It stores water, nutrients, waste products, and other essential materials required by the cell. Vacuoles are crucial for maintaining cell structure and regulating cellular processes. Mitochondrion (choice A) is known as the powerhouse of the cell, responsible for producing energy. The cell membrane (choice C) is a protective barrier around the cell, regulating what enters and exits the cell. Ribosomes (choice D) are involved in protein synthesis, not storage.
2. Which structure controls the passage of substances into and out of the cell?
- A. Vacuole
- B. Cell Membrane
- C. Nuclear Membrane
- D. Cytoplasm
Correct answer: B
Rationale: The correct answer is the Cell Membrane. The cell membrane acts as a barrier that controls the passage of substances into and out of the cell. It is selectively permeable, allowing only certain molecules to pass through. Vacuole (Choice A), Nuclear Membrane (Choice C), and Cytoplasm (Choice D) do not primarily regulate the passage of substances in and out of the cell. Vacuoles are responsible for storage, the nuclear membrane surrounds the nucleus providing protection, and the cytoplasm is the fluid where organelles are suspended.
3. Why is yeast used to make bread rise?
- A. It engages in photosynthesis, which produces oxygen gas.
- B. Carbon dioxide forms while yeast carries out photosynthesis.
- C. Yeast carries out fermentation, producing ethanol and carbon dioxide.
- D. Yeast breathes in oxygen and produces carbon dioxide through aerobic respiration.
Correct answer: C
Rationale: Yeast is used to make bread rise because it carries out fermentation, producing carbon dioxide gas. The carbon dioxide gas gets trapped in the dough, causing it to rise and create a fluffy texture in the bread. Choices A, B, and D are incorrect because yeast does not engage in photosynthesis, so it does not produce oxygen gas, does not carry out photosynthesis to form carbon dioxide, and does not produce carbon dioxide through aerobic respiration. Yeast's fermentation process is essential for bread rising.
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. Which organism reproduces via binary fission?
- A. Mushroom
- B. Blue whale
- C. Rainbow trout
- D. Salmonella
Correct answer: D
Rationale: The correct answer is D, Salmonella. Salmonella bacterium reproduces via binary fission, a form of asexual reproduction where the cell divides into two daughter cells with identical genetic material. This process is common among bacteria and single-celled organisms. Mushrooms reproduce through spores, blue whales and rainbow trout reproduce sexually, involving the fusion of male and female gametes. Therefore, choices A, B, and C are incorrect as they do not reproduce through binary fission.
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