HESI A2
HESI A2 Biology 2024
1. If bacteria are placed in a strong solution of salt water, they will shrink as water moves out of the bacteria. What is this process called?
- A. Dehydration synthesis
- B. Hydrolysis
- C. Osmosis
- D. Isotonic transport
Correct answer: C
Rationale: Osmosis is the process by which water molecules move across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration. In this case, when bacteria are placed in a strong solution of salt water, the high concentration of solutes outside the bacteria causes water to move out of the bacteria, leading to shrinkage. This process is known as osmosis. Dehydration synthesis (Choice A) is a process where molecules combine by removing water. Hydrolysis (Choice B) is the breakdown of molecules by the addition of water. Isotonic transport (Choice D) does not accurately describe the specific movement of water in or out of bacterial cells in a hypertonic solution.
2. 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.
3. In nature, water vapor becomes liquid water through the process of ___________.
- A. condensation
- B. sublimation
- C. precipitation
- D. absorption
Correct answer: A
Rationale: In nature, water vapor becomes liquid water through the process of condensation. Condensation occurs when water vapor cools and changes its state from a gas to a liquid, forming droplets that we commonly see as water droplets on surfaces or clouds in the sky. Sublimation refers to the transition from a solid to a gas without passing through the liquid phase. Precipitation is the process where water in the atmosphere falls to the ground as rain, snow, sleet, or hail. Absorption is the process of one substance being taken in by another.
4. Which of the following is always true about molecules?
- A. They cannot travel through all cell membranes
- B. They move from low concentration to high concentration without using energy
- C. They move from high concentration to low concentration without using energy
- D. They cannot move
Correct answer: C
Rationale: The statement that molecules move from high concentration to low concentration without using energy is always true due to the natural process of diffusion. This movement occurs to reach equilibrium and does not require any additional energy input directly from the molecule itself. Choice A is incorrect because not all molecules can travel through all cell membranes. Choice B is incorrect as molecules typically move from high concentration to low concentration in a process known as passive transport. Choice D is incorrect as molecules are in constant motion due to factors like temperature and kinetic energy.
5. What type of cell is an animal cell?
- A. Prokaryotic
- B. Eukaryotic
- C. Plant Cell
- D. Bacterial Cell
Correct answer: B
Rationale: The correct answer is B, eukaryotic. Animal cells are classified as eukaryotic cells because they contain membrane-bound organelles such as the nucleus, mitochondria, and endoplasmic reticulum. Choice A, prokaryotic, is incorrect as prokaryotic cells lack membrane-bound organelles. Choice C, Plant Cell, is incorrect as the question specifically asks about animal cells. Choice D, Bacterial Cell, is incorrect as bacteria are prokaryotic cells.
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