HESI A2
HESI A2 Practice Test Biology
1. Which of the following is not found within a bacterial cell?
- A. mitochondria
- B. DNA
- C. vesicles
- D. ribosome
Correct answer: A
Rationale: The correct answer is A: mitochondria. Mitochondria are not found in bacterial cells. Bacterial cells lack membrane-bound organelles like mitochondria, which are commonly found in eukaryotic cells. Choices B, C, and D are all components that can be found within a bacterial cell. Bacterial cells contain DNA as their genetic material, vesicles for various cellular functions, and ribosomes for protein synthesis. Therefore, the presence of mitochondria is the distinguishing factor that is not found in bacterial cells, making option A the correct answer.
2. How many pairs of homologous chromosomes do humans have?
- A. 13
- B. 23
- C. 26
- D. 46
Correct answer: D
Rationale: The correct answer is D: 46. Humans have 23 pairs of chromosomes, which include 22 pairs of autosomes and 1 pair of sex chromosomes. Homologous chromosomes are pairs of chromosomes that contain the same genes, one from each parent. Therefore, humans have a total of 46 chromosomes, with 23 pairs of homologous chromosomes. Choices A, B, and C are incorrect as they do not represent the total number of chromosomes in humans or the number of pairs of homologous chromosomes.
3. What molecule is primarily responsible for providing energy to the cell?
- A. ATP
- B. DNA
- C. ADP
- D. Glycogen
Correct answer: A
Rationale: Correct! ATP (Adenosine Triphosphate) is the main molecule that stores and provides energy for cellular activities. ATP is known as the energy currency of the cell, where energy released from the breakdown of nutrients is stored in the high-energy phosphate bonds of ATP. Choices B, C, and D are incorrect because DNA carries genetic information, ADP is the precursor of ATP, and glycogen is a polysaccharide used for energy storage, not direct energy provision.
4. What event occurs during telophase?
- A. The nuclear envelope disappears.
- B. Organelles double in number.
- C. Chromosomes separate.
- D. Two nuclei are formed.
Correct answer: D
Rationale: During telophase, the final stage of mitosis, the separated chromosomes reach opposite poles of the cell. At this stage, a new nuclear envelope forms around each set of chromosomes, creating two distinct nuclei. This marks the completion of cell division. Choices A, B, and C are incorrect because the disappearance of the nuclear envelope typically occurs during prophase, organelles do not double in number during telophase, and chromosomes separate during anaphase, not telophase.
5. Phenotype refers to the _ of an individual.
- A. Genetic makeup
- B. Actual physical appearance
- C. Recessive alleles
- D. None of the above
Correct answer: B
Rationale: Phenotype refers to the actual physical appearance and characteristics of an individual, which are determined by the interaction of both genetic makeup (genotype) and environmental factors. It includes visible traits such as height, eye color, and hair type. Choice A, genetic makeup, refers to the genotype, which is the genetic constitution of an organism. Choice C, recessive alleles, is a specific type of gene variant and does not encompass the entire concept of phenotype. Choice D, none of the above, is incorrect as phenotype does refer to the actual physical appearance of an individual.
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