HESI A2
HESI A2 Biology Practice Test
1. A child is sick. They have a body temperature that exceeds 37ÂșC. The body senses this and begins to sweat in order to lower the temperature. What is this an example of?
- A. Positive feedback loop
- B. Negative feedback loop
- C. Both
- D. None of the above
Correct answer: B
Rationale: This is an example of a negative feedback loop. In a negative feedback loop, the body's response (sweating) works to counteract the initial stimulus of a high body temperature by cooling the body down. The goal is to return the body to homeostasis, maintaining a stable internal environment. Positive feedback loops amplify the initial stimulus rather than counteracting it, which is not the case here. Therefore, choices A and C are incorrect. Choice D is also incorrect as the situation described fits the characteristics of a negative feedback loop.
2. Which component of the cell contributes to the protection, communication, and passage of substances into and out of the cell?
- A. Nucleus
- B. Cell membrane
- C. Endoplasmic reticulum
- D. Cytoplasm
Correct answer: B
Rationale: The correct answer is the cell membrane. The cell membrane is responsible for protecting the cell, facilitating communication with the external environment, and regulating the passage of substances into and out of the cell. The nucleus (Choice A) is the control center of the cell and houses the genetic material but is not primarily involved in these functions. The endoplasmic reticulum (Choice C) is involved in protein synthesis and lipid metabolism, not primarily in protection or communication. The cytoplasm (Choice D) is the gel-like substance that fills the cell but does not specifically contribute to protection, communication, or substance passage.
3. What kind of symbiosis exists between a pneumonia bacterium and a human?
- A. Mutualism
- B. Parasitism
- C. Commensalism
- D. Competition
Correct answer: B
Rationale: In the case of a pneumonia bacterium and a human, the relationship is best described as parasitism. The bacterium benefits by causing harm to the human host, while the human is negatively affected by the presence of the bacterium, leading to illness or infection. This is a classic example of a parasitic relationship where one organism benefits at the expense of the other. Mutualism (Choice A) is a type of symbiotic relationship where both organisms benefit from each other. Commensalism (Choice C) is a symbiotic relationship where one organism benefits, and the other is neither helped nor harmed. Competition (Choice D) refers to a relationship where both organisms are negatively affected by each other as they compete for resources.
4. How are lipids different from other organic molecules?
- A. They are indivisible.
- B. They are not water soluble.
- C. They contain zinc.
- D. They form long proteins.
Correct answer: B
Rationale: The correct answer is B: 'They are not water soluble.' Lipids are not water-soluble, which distinguishes them from other organic molecules. Choice A is incorrect because lipids are not indivisible; they can be broken down into fatty acids and glycerol. Choice C is incorrect as lipids do not necessarily contain zinc; they are a diverse group of molecules. Choice D is incorrect because lipids do not form long proteins; proteins are made up of amino acids, not lipids.
5. Where is the genetic information of a eukaryotic cell stored?
- A. Mitochondria
- B. Nucleus
- C. Golgi Apparatus
- D. Cytoplasm
Correct answer: B
Rationale: The correct answer is B: Nucleus. In eukaryotic cells, genetic information (DNA) is stored in the nucleus. This organelle acts as the control center of the cell, housing the DNA and regulating gene expression. Choices A, C, and D are incorrect because the genetic information is not stored in the mitochondria, Golgi Apparatus, or cytoplasm. The mitochondria are responsible for energy production, the Golgi Apparatus is involved in protein processing and packaging, and the cytoplasm is where various cellular activities take place, but none of these organelles store the genetic information.
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