HESI A2
HESI A2 Biology Practice Test 2024
1. How many pairs of chromosomes do all humans have?
- A. 24 pairs
- B. 23 pairs
- C. 22 pairs
- D. 20 pairs
Correct answer: B
Rationale: All humans have 23 pairs of chromosomes, totaling 46 chromosomes. Choice A is incorrect because humans do not have 24 pairs. Choice C is incorrect as humans have 23 pairs, not 22 pairs. Choice D is incorrect as humans have 23 pairs of chromosomes, not 20 pairs.
2. How many chromosomes do sperm and egg produce in meiosis?
- A. 23
- B. 46
- C. 25
- D. 50
Correct answer: A
Rationale: During meiosis, sperm and egg cells produce half the number of chromosomes found in somatic cells. Each contributes 23 chromosomes, which combine to form a zygote with a total of 46 chromosomes. Choice B (46) is incorrect because this is the number of chromosomes produced in mitosis, not meiosis. Choices C (25) and D (50) are also incorrect as they do not align with the chromosome count in sex cells during meiosis.
3. Which organelle is involved in the synthesis of proteins?
- A. Endoplasmic Reticulum
- B. Ribosomes
- C. Lysosomes
- D. Vacuoles
Correct answer: B
Rationale: Ribosomes are the organelles involved in the synthesis of proteins. They are the cellular machinery responsible for translating mRNA into proteins, making them essential for cell function and structure. The other organelles listed, such as the Endoplasmic Reticulum, Lysosomes, and Vacuoles, have different functions unrelated to protein synthesis. The Endoplasmic Reticulum plays a role in protein processing and transport, Lysosomes are involved in digestion and waste removal, and Vacuoles are responsible for storage and maintaining cell turgor pressure.
4. What is the magnification of an ocular lens on a microscope?
- A. 4x
- B. 10x
- C. 40x
- D. 100x
Correct answer: B
Rationale: The magnification of an ocular lens on a microscope is typically 10x, which is considered standard for most microscopes. Ocular lenses are designed to magnify the image produced by the objective lens further. Choices A, C, and D are incorrect because they do not represent the standard magnification of an ocular lens. A magnification of 4x, 40x, or 100x would not be typical for an ocular lens in a microscope.
5. Which organelle is the site of photosynthesis in plant cells?
- A. Mitochondria
- B. Chloroplasts
- C. Ribosomes
- D. Endoplasmic Reticulum
Correct answer: B
Rationale: The correct answer is B: Chloroplasts. Chloroplasts are responsible for conducting photosynthesis in plant cells. They contain chlorophyll, a pigment that captures light energy and converts it into chemical energy through the process of photosynthesis. Mitochondria (choice A) are known as the powerhouse of the cell and are involved in cellular respiration, not photosynthesis. Ribosomes (choice C) are responsible for protein synthesis. The endoplasmic reticulum (choice D) is involved in protein and lipid synthesis and transport within the cell, not photosynthesis.
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