HESI A2
HESI A2 Biology 2024
1. Which molecules contain only carbon, hydrogen, and oxygen?
- A. Lipids and proteins
- B. Carbohydrates and lipids
- C. Proteins and carbohydrates
- D. Nucleic acids and proteins
Correct answer: B
Rationale: Carbohydrates and lipids are the molecules that contain only carbon, hydrogen, and oxygen. Carbohydrates such as sugars and starches are made up of carbon, hydrogen, and oxygen in a ratio of 1:2:1, while lipids such as fats and oils are composed of carbon, hydrogen, and oxygen as well. Lipids typically contain more carbon and hydrogen atoms compared to oxygen atoms. Proteins contain nitrogen in addition to carbon, hydrogen, and oxygen, while nucleic acids contain phosphorus in addition to carbon, hydrogen, and oxygen. Therefore, choices A, C, and D are incorrect as they include molecules that contain elements other than carbon, hydrogen, and oxygen.
2. If a hard-boiled egg is placed in a beaker of saltwater, what will happen to the egg?
- A. Expand because water will move into the egg
- B. Shrivel because water will leave the egg
- C. Remain the same
- D. None of the above
Correct answer: B
Rationale: The correct answer is B. When a hard-boiled egg is placed in a beaker of saltwater, the egg will shrivel because water will leave the egg through osmosis. Osmosis is the movement of water from an area of lower solute concentration to an area of higher solute concentration, in this case, from the egg into the saltwater. The higher concentration of solute in the saltwater causes water to move out of the egg, leading to the egg shrinking or shriveling. Choices A, C, and D are incorrect because the egg will not expand, remain the same, or have an outcome different from shriveling when placed in a beaker of saltwater.
3. What organelle in the cell produces energy through the process of respiration?
- A. Nucleus
- B. Mitochondria
- C. Golgi Apparatus
- D. Chloroplasts
Correct answer: B
Rationale: The correct answer is B: Mitochondria. The mitochondria are known as the powerhouse of the cell and are responsible for producing energy through respiration in eukaryotic cells. Choice A, the Nucleus, is not involved in energy production but rather houses the cell's genetic material. Choice C, the Golgi Apparatus, is responsible for packaging and processing proteins, not energy production. Choice D, Chloroplasts, are responsible for photosynthesis in plant cells, not respiration for energy production.
4. How many phases are there in the process of mitosis?
- A. 2
- B. 3
- C. 4
- D. 5
Correct answer: C
Rationale: The correct answer is C: '4'. Mitosis consists of four phases: prophase, metaphase, anaphase, and telophase. These phases are crucial in the orderly division of the cell's genetic material. Choice A is incorrect because mitosis is a more complex process involving multiple phases. Choice B is incorrect as it is one phase short of the total phases in mitosis. Choice D is incorrect as mitosis does not consist of five phases.
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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