HESI A2
Biology HESI A2 Practice Exam
1. RNA is made from DNA through a process called ___________.
- A. transcription
- B. synthesis
- C. translation
- D. replication
Correct answer: A
Rationale: RNA is made from DNA through a process called transcription. During transcription, an enzyme called RNA polymerase reads the DNA template and synthesizes a complementary RNA molecule. This process is essential for gene expression and allows the information encoded in DNA to be converted into functional RNA molecules. Choice B, 'synthesis,' is incorrect as it is a general term and does not specifically describe the process of RNA formation from DNA. Choice C, 'translation,' is incorrect as it refers to the process where the mRNA is used to assemble amino acids during protein synthesis, not the conversion of DNA to RNA. Choice D, 'replication,' is incorrect as it is the process of making an identical copy of DNA, not converting DNA into RNA.
2. Genes control heredity in man and other organisms. This gene is ___
- A. A segment of DNA
- B. A bead-like structure on the chromosomes
- C. A protein molecule
- D. A segment of RNA
Correct answer: A
Rationale: Genes are sections of DNA that contain instructions for building and operating living organisms. These sections of DNA contain the genetic information that is passed on from one generation to the next. Genes are composed of specific sequences of nucleotides within the DNA molecule. Therefore, genes are best described as segments of DNA. Choice A is correct. Choice B is incorrect because genes are not bead-like structures on chromosomes but specific sequences of DNA. Choice C is incorrect because genes are not protein molecules but rather sequences of nucleotides. Choice D is incorrect because genes are not segments of RNA but DNA.
3. What happens to glucose during glycolysis?
- A. Its energy is entirely lost.
- B. It splits into molecules of pyruvic acid.
- C. It is stored in NADH.
- D. It joins with molecules of citric acid.
Correct answer: B
Rationale: During glycolysis, glucose undergoes a series of enzymatic reactions in the cytoplasm of the cell, resulting in its breakdown into two molecules of pyruvic acid. This process also generates ATP and NADH as energy carriers. Choice A is incorrect because glucose is not entirely lost, but rather converted into other molecules. Choice C is incorrect because NADH is a product of glycolysis, not a storage form for glucose. Choice D is incorrect as glucose does not join with molecules of citric acid during glycolysis, but rather in subsequent stages of cellular respiration.
4. Which organelle would you expect to be present in a cell responsible for detoxifying multiple molecules?
- A. rough ER
- B. smooth ER
- C. lysosome
- D. Golgi apparatus
Correct answer: B
Rationale: The smooth endoplasmic reticulum (ER) is the organelle responsible for detoxifying multiple molecules in a cell. It contains enzymes that help break down toxins and drugs, making it an essential organelle for detoxification processes. The rough ER, lysosome, and Golgi apparatus do not play direct roles in detoxification. The rough ER is mainly involved in protein synthesis and transport. Lysosomes are responsible for digestion and recycling within the cell. The Golgi apparatus is involved in modifying, sorting, and packaging proteins for secretion or for use within the cell.
5. 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.
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