HESI RN
Biology Test
1. During which stage of photosynthesis is solar energy converted to chemical energy?
- A. During phosphate synthesis
- B. During light reactions
- C. During the Krebs cycle
- D. During the Calvin cycle
Correct answer: B
Rationale: The correct answer is B, during the light reactions. During the light reactions of photosynthesis, solar energy is absorbed by chlorophyll and converted into chemical energy in the form of ATP and NADPH. Choice A is incorrect as phosphate synthesis does not involve the conversion of solar energy. Choice C, the Krebs cycle, is a part of cellular respiration, not photosynthesis. Choice D, the Calvin cycle, is responsible for fixing carbon dioxide into carbohydrates and does not involve the direct conversion of solar energy to chemical energy.
2. In DNA, the nucleotide base adenine always binds with which of the following?
- A. Guanine
- B. Uracil
- C. Thymine
- D. Cytosine
Correct answer: C
Rationale: The correct answer is C: Thymine. In DNA, adenine always pairs with thymine, forming a base pair held together by hydrogen bonds. Guanine pairs with cytosine. Uracil is found in RNA, not DNA. Cytosine pairs with guanine. Therefore, option C is the correct pairing for adenine in DNA.
3. What percentage of the offspring of the parents is predicted to have a cleft chin?
- A. 25%
- B. 50%
- C. 0%
- D. 75%
Correct answer: A
Rationale: When one parent carries the recessive gene for a cleft chin and the other does not, there is a 25% chance of the offspring inheriting the cleft chin. This is due to the fact that the trait follows a simple Mendelian inheritance pattern, where the offspring would need to inherit the recessive gene from both parents to express the trait. Therefore, 25% of the offspring are predicted to have a cleft chin. Choices B, C, and D are incorrect because the likelihood of inheriting a cleft chin in this specific scenario is 25%, not 50%, 0%, or 75%.
4. What is the most significant contributor to cellular function?
- A. Proteins
- B. Phospholipids
- C. Carbohydrates
- D. Fatty acids
Correct answer: A
Rationale: The correct answer is A: Proteins. Proteins are the most significant contributor to cellular function as they play crucial roles in almost all biological processes. They act as enzymes that catalyze reactions, are involved in cell signaling pathways, and provide structural support to cells. Phospholipids (Choice B), while important for cell membrane structure, do not have the same diverse functions as proteins in cellular processes. Carbohydrates (Choice C) primarily serve as an energy source and structural components but are not as versatile in cellular functions as proteins. Fatty acids (Choice D) are essential components of cell membranes and energy storage molecules but do not have the same broad range of functions as proteins in cellular processes.
5. What must first occur before a cell can be divided to grow, develop, and reproduce organisms?
- A. RNA replication
- B. DNA replication
- C. Gene replication
- D. Chromosome replication
Correct answer: B
Rationale: The correct answer is B: DNA replication. Before a cell can divide to grow, develop, and reproduce organisms, DNA replication must occur. This process ensures that each daughter cell receives an identical set of genetic information. Choices A, C, and D are incorrect because while RNA, genes, and chromosomes are essential components of cell division, DNA replication is the specific process that must first occur to ensure accurate transmission of genetic material.
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