HESI A2 Biology Practice Test

Correct Answer: A

Rationale: The correct answer is A: fat-soluble hormones. Fat-soluble hormones can diffuse through the cell membrane due to their lipophilic nature. Once inside the cell, they can bind to receptors located in the cytoplasm or nucleus to initiate a chemical response. This process allows fat-soluble hormones to directly affect gene expression and protein synthesis within the target cell. In contrast, choices B, C, and D (amino acid derivatives, hydrophilic, and water-soluble hormones) cannot diffuse through the cell membrane and typically bind to receptors on the cell surface to trigger a signaling cascade.

Correct Answer: C

Rationale: Anaerobic respiration occurs in bacteria because they live in environments with low oxygen levels. Bacteria adapt to anaerobic conditions by utilizing alternative pathways to generate energy without oxygen. This process allows them to survive and thrive in oxygen-deprived environments. The other choices are incorrect because animals require oxygen for aerobic respiration, plants use sunlight for photosynthesis, and option D is incorrect as bacteria indeed undergo anaerobic respiration in low oxygen environments.

Correct Answer: A

Rationale: To convert cm to mm, you multiply by 10 since 1 cm = 10 mm. Therefore, to convert 8 cm to mm, you multiply 8 by 10 which equals 80 mm. Choice A (80 mm) is correct. Option B (800 mm) is incorrect as it is 10 times the correct answer, making it too large. Option C (8 mm) is incorrect as it represents the original measurement in cm, not the conversion to mm. Option D (0.8 mm) is incorrect as it is one-tenth of the correct answer, making it too small.

Correct Answer: B

Rationale: Enzymes are typically proteins because they are biological catalysts made up of amino acids. Proteins have specific structures that allow them to bind to substrates and speed up chemical reactions. Fats, sugars, and neurons do not possess the specific structural properties required for enzyme function. Therefore, the correct answer is B (Proteins).

Correct Answer: D

Rationale: The correct answer is D because phenotype is the observable characteristics resulting from the interaction between genotype, epigenetic factors, and environmental factors. Genotype (genetic makeup) provides the foundation, epigenetic factors can modify gene expression, and environmental factors play a crucial role in shaping the final phenotype. Explanation: A: Incorrect. Phenotype is not the genetic code itself but the physical expression of genetic traits. B: Incorrect. Phenotype does not determine genotype; genotype determines phenotype. C: Incorrect. Genotype determines phenotype, not the other way around. D: Correct. Genotype, epigenetic factors, and environmental factors collectively determine the phenotype, making it the most comprehensive and accurate choice.