what cycle is the sequence of reactions by which most living cells generate energy during aerobic respiration

HESI A2

HESI A2 Biology Practice Test 2024

1. 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.

2. 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.

3. Which of the following is the best example of a hypothesis?

A. Dogs like treats
B. Red is the best color
C. If I eat 100 donuts, then I will feel sick
D. If a plant is exposed to red light, then it will show less growth than natural light

Correct answer: D

Rationale: Option D is the best example of a hypothesis because it presents a clear cause-and-effect relationship that can be tested through experimentation. It follows the format of 'If [cause], then [effect]' which is characteristic of a hypothesis in scientific research. The statement is specific, testable, and does not rely on personal opinions or biases, making it a strong and valid hypothesis. Choices A, B, and C do not follow the structure of a hypothesis as they lack the cause-and-effect relationship that can be tested through experimentation. They are more like statements or opinions rather than hypotheses.

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. What is the fundamental unit of life?

A. Atom
B. Cell
C. Tissue
D. Organ

Correct answer: B

Rationale: The correct answer is 'B: Cell.' Cells are indeed the fundamental unit of life as they are responsible for all living functions, including growth, reproduction, and maintaining homeostasis. While atoms are the basic building blocks of matter, cells are the smallest structural and functional unit of living organisms. Choices C and D, tissue and organ respectively, are composed of multiple cells working together and are not considered the basic unit of life.