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. In contrast with triglycerides, phospholipids are lacking one of which of the following components?
- A. Monosaccharide
- B. Glycerol
- C. Phosphates
- D. Fatty acid
Correct answer: B
Rationale: Phospholipids are structurally similar to triglycerides but lack one of the fatty acid chains that triglycerides possess. Triglycerides consist of three fatty acid chains attached to a glycerol molecule, while phospholipids have two fatty acid chains and a phosphate group attached to a glycerol backbone. Therefore, phospholipids are lacking the third fatty acid chain found in triglycerides. Choice A (Monosaccharide) is incorrect because neither triglycerides nor phospholipids contain monosaccharides in their structure. Choice C (Phosphates) is incorrect because phospholipids actually contain phosphates, unlike triglycerides. Choice D (Fatty acid) is incorrect as both triglycerides and phospholipids contain fatty acids, but the number of fatty acid chains differs between the two.
3. How is mitosis different from meiosis?
- A. Mitosis is the process by which body cells are formed.
- B. Meiosis creates cells with half the chromosomes of the parent cell.
- C. Telophase occurs in both mitosis and meiosis.
- D. Spermatogenesis and oogenesis occur via meiosis.
Correct answer: B
Rationale: Meiosis is the type of cell division that creates cells with half the number of chromosomes compared to the parent cell. This is essential for sexual reproduction as it ensures that when the sex cells (sperm and egg) combine during fertilization, the resulting offspring has the correct number of chromosomes. In contrast, mitosis results in two identical daughter cells with the same number of chromosomes as the parent cell. Choice A is incorrect because mitosis is responsible for the division of body cells, not sex cells. Choice C is incorrect because telophase is a phase that occurs in both mitosis and meiosis. Choice D is incorrect because spermatogenesis and oogenesis involve meiosis, not mitosis.
4. What are the three types of muscle tissue?
- A. Cardiac, spinal, stomach
- B. Smooth, skeletal, cardiac
- C. Neuron, epithelial, collagen
- D. None of the above
Correct answer: B
Rationale: The correct answer is B: Smooth, skeletal, cardiac. Smooth muscle is found in organs like the stomach and is involuntarily controlled. Skeletal muscle is found in voluntary muscles, like the bicep or quadriceps. Cardiac muscle is found only in the heart walls and works involuntarily to make the heart beat and pump blood. Choices A, C, and D are incorrect because they do not represent the three types of muscle tissue.
5. What are saturated fats saturated with?
- A. Hydrogen atoms
- B. Carbon atoms
- C. Oxygen atoms
- D. Nitrogen atoms
Correct answer: A
Rationale: Saturated fats are saturated with hydrogen atoms. This means that each carbon atom in the fatty acid chains forming saturated fats is bonded to as many hydrogen atoms as possible. This saturation results in the fatty acid chains being straight and closely packed together, making saturated fats solid at room temperature. Choice B (Carbon atoms), C (Oxygen atoms), and D (Nitrogen atoms) are incorrect because saturated fats are specifically saturated with hydrogen atoms, not carbon, oxygen, or nitrogen atoms.
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