HESI A2 Biology Practice Test 2024

Correct Answer: B

Rationale: The correct answer is B: Chloroplasts. Chloroplasts are the organelles responsible for photosynthesis in plant cells. They contain chlorophyll, the pigment that captures sunlight for photosynthesis. Mitochondria (A) are involved in cellular respiration, not photosynthesis. Ribosomes (C) are responsible for protein synthesis, not photosynthesis. Endoplasmic Reticulum (D) is involved in protein and lipid synthesis, not photosynthesis. Therefore, the correct answer is B because chloroplasts are specifically designed for photosynthesis in plant cells.

Correct Answer: B

Rationale: Osmosis is the correct answer as it specifically refers to the movement of water molecules through a selectively permeable membrane. During osmosis, water moves from an area of higher concentration to an area of lower concentration to equalize the concentration on both sides of the membrane. This process does not require energy input and is crucial for maintaining the balance of water in cells. Diffusion (A) involves the movement of molecules from an area of high concentration to low concentration, but it is not specific to water molecules through a membrane. Active Transport (C) requires energy to move molecules against their concentration gradient, which is not the case in osmosis. Facilitated Diffusion (D) also involves the movement of molecules across a membrane, but it requires the assistance of specific carrier proteins, unlike the passive movement of water in osmosis.

Correct Answer: B

Rationale: The correct answer is B: Krebs Cycle. This cycle, also known as the citric acid cycle, occurs in the mitochondria of cells and plays a crucial role in generating energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins. It produces ATP, NADH, and FADH2, which are essential for cellular energy production. The Calvin Cycle (A) and Photosynthesis (C) are involved in the process of converting light energy into chemical energy in plants, not in generating energy during cellular respiration. Fermentation (D) is an anaerobic process that generates energy in the absence of oxygen, but it is not as efficient as aerobic respiration in producing ATP.

Correct Answer: C

Rationale: The correct answer is C: Mitochondria. Mitochondria are the site of cellular respiration in eukaryotic cells. Here's the rationale: 1. Mitochondria contain enzymes involved in the various stages of cellular respiration. 2. The inner membrane of mitochondria has folds called cristae, which provide a large surface area for aerobic respiration. 3. ATP, the energy currency of the cell, is produced in the mitochondria during cellular respiration. 4. Nucleus (A) houses the genetic material, not involved in cellular respiration. Chloroplasts (B) are found in plant cells and are responsible for photosynthesis, not respiration. Ribosomes (D) are involved in protein synthesis, not cellular respiration.

Correct Answer: B

Rationale: In meiosis, sperm and egg cells produce haploid gametes with half the number of chromosomes as the parent cell. Since humans have 46 chromosomes in each somatic cell, sperm and egg cells produce 23 chromosomes each in meiosis. This ensures that when fertilization occurs, the resulting zygote has the correct diploid number of chromosomes. Choice A (46) is incorrect because somatic cells have 46 chromosomes, not gametes. Choice C (45) and D (24) are incorrect because they do not represent the correct haploid number of chromosomes produced in meiosis.