a child is sick they have a body temperature that exceeds 37c the body senses this and begins to sweat in order to lower the temperature what is this

HESI A2

HESI A2 Biology Practice Test

1. A child is sick. They have a body temperature that exceeds 37ºC. 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 of the following organelles are responsible for producing cell energy?

A. Mitochondrion and chloroplast
B. Mitochondrion and nucleus
C. Chloroplast and nucleus
D. Chloroplast and lysosome

Correct answer: A

Rationale: The correct answer is A: Mitochondrion and chloroplast. Mitochondria and chloroplasts are the organelles responsible for producing cell energy through cellular respiration and photosynthesis, respectively. Choice B is incorrect because the nucleus is not involved in energy production. Choice C is incorrect as the nucleus is not an organelle that produces energy. Choice D is incorrect as lysosomes function in digesting waste materials, not in energy production.

3. Which of the following is true of the Krebs cycle?

A. It is a redox reaction involving proteins produced during glycolysis
B. It is a redox reaction involving sugars produced during glycolysis
C. Protons are passed along a gradient to produce ATP
D. It is also known as the glycolic acid cycle

Correct answer: B

Rationale: The Krebs cycle, also known as the citric acid cycle, involves a series of redox reactions that occur in the mitochondria. The cycle begins with the oxidation of acetyl CoA, which is derived from the breakdown of sugars produced during glycolysis. These sugars are broken down further in the Krebs cycle to produce ATP and reduce electron carriers such as NADH and FADH2. The cycle does not involve proteins produced during glycolysis. Protons are not passed along a gradient to produce ATP directly in the Krebs cycle; rather, they are used in the electron transport chain to generate ATP. The Krebs cycle is not known as the glycolic acid cycle; glycolysis is the metabolic pathway that produces pyruvate from glucose.

4. 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.

5. In a phospholipid molecule, the head:

A. Is hydrophilic
B. Is hydrophobic
C. Is on the inner side of the layer
D. Both A and C

Correct answer: D

Rationale: The head of a phospholipid is hydrophilic (water-loving) and is located on the outer side of the lipid bilayer, interacting with water molecules. This arrangement positions the hydrophobic tails inward, away from water. Therefore, the correct answer is D. Choice A is incorrect because the head is hydrophilic, not hydrophobic. Choice B is incorrect as the head is on the outer side, not the inner side of the layer.