HESI A2
HESI A2 Biology 2024
1. What is the term for the breakdown of glycogen into glucose subunits?
- A. Hydrolysis
- B. Reduction
- C. Metabolism
- D. Transpiration
Correct answer: A
Rationale: Hydrolysis is the term used to describe the breakdown of large molecules into smaller units by adding water. In the case of glycogen being broken down into glucose subunits, this process involves the addition of water molecules to break the glycosidic bonds between glucose molecules, resulting in the release of individual glucose subunits. This process is crucial for providing cells with a source of energy when needed. Choice B, Reduction, refers to a chemical reaction involving a gain of electrons or a decrease in oxidation state, not the breakdown of glycogen into glucose subunits. Choice C, Metabolism, is a broad term encompassing all biochemical processes in an organism, including anabolism and catabolism, but does not specifically describe the breakdown of glycogen into glucose subunits. Choice D, Transpiration, is the process of water movement through a plant and is not related to the breakdown of glycogen into glucose subunits.
2. Which is not a product of the Krebs cycle?
- A. ATP
- B. Carbon dioxide
- C. Glucose
- D. NADH
Correct answer: C
Rationale: Glucose is not a direct product of the Krebs cycle. Glucose is a starting molecule that undergoes glycolysis outside the mitochondria to produce pyruvate, which then enters the mitochondrial matrix to participate in the Krebs cycle. The Krebs cycle primarily generates ATP, carbon dioxide, and NADH as products. Choices A, B, and D are all products of the Krebs cycle, making them incorrect answers.
3. Which of the following molecules is an important component of the plasma membrane?
- A. Phospholipids
- B. Steroids
- C. Sugars
- D. Amino acids
Correct answer: A
Rationale: Phospholipids are indeed a crucial component of the plasma membrane. They have a unique structure with hydrophilic heads and hydrophobic tails, which allows them to form the lipid bilayer of the membrane. Steroids, sugars, and amino acids are not primary components of the plasma membrane. Steroids are a different type of lipid, sugars are often found in glycoproteins on the membrane surface, and amino acids are the building blocks of proteins, some of which are membrane proteins, but not the membrane itself.
4. Which, if any, of the following statements about the biosphere is correct?
- A. The biosphere is the part of the Earth that supports life.
- B. The biosphere encompasses the entire surface of the Earth.
- C. A and B are correct.
- D. None of these statements is correct.
Correct answer: A
Rationale: Statement A is correct. The biosphere refers to the part of the Earth where life exists, including the land, water bodies, and atmosphere. It is the zone where living organisms and ecosystems exist. Statement B is incorrect because the biosphere covers various ecosystems on Earth but does not encompass the entire surface of the planet. The biosphere includes regions such as the lithosphere (land), hydrosphere (water bodies), and atmosphere, but not every part of the Earth's surface. Therefore, option C, stating both A and B are correct, is inaccurate. The correct answer is option A, as it accurately defines the biosphere.
5. What cycle is the sequence of reactions by which most living cells generate energy during aerobic respiration?
- A. Calvin Cycle
- B. Krebs Cycle
- C. Photosynthesis
- D. Fermentation
Correct answer: B
Rationale: The Krebs Cycle is the correct answer. It is a series of reactions occurring in the mitochondria and is a crucial part of aerobic respiration. The Calvin Cycle is a part of photosynthesis, not respiration, making choice A incorrect. Photosynthesis (choice C) is the process by which plants, algae, and some bacteria convert light energy into chemical energy. Fermentation (choice D) is an anaerobic process that does not require oxygen and is not the primary energy-generating pathway during aerobic respiration, so it is incorrect.
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