HESI A2
HESI A2 Biology Practice Test
1. How many bones are included in the human skeletal system?
- A. 412
- B. 103
- C. Over 300
- D. 206
Correct answer: D
Rationale: There are 206 bones in the human skeletal system. This includes bones in the skull, spine, ribs, arms, legs, hands, and feet. The correct answer is 206 because that is the standard number of bones in an adult human body. Choices A, B, and C are incorrect as they do not reflect the accurate count of bones in the human skeletal system.
2. Why can animal cells use a contractile ring but plant cells cannot?
- A. Plant cells can use both methods to divide
- B. Animal cells divide faster, requiring them to pinch apart
- C. Plant cells are too rigid to use a contractile ring
- D. N/A
Correct answer: C
Rationale: Plant cells have a rigid cell wall surrounding them, which prevents them from using a contractile ring for cell division. The rigid cell wall requires plant cells to form a cell plate during cell division instead of pinching apart like animal cells with a contractile ring. Choice A is incorrect because plant cells cannot use a contractile ring due to their rigid cell wall. Choice B is incorrect as the speed of cell division is not the primary reason for the difference in cell division mechanisms between plant and animal cells. Choice D is not applicable as plant cells indeed have a specific limitation in using a contractile ring for cell division.
3. What happens during anaphase?
- A. Chromosomes move to opposite ends of the spindle.
- B. Nuclear membrane and nucleoli disintegrate.
- C. Chromatids line up at the center of the spindle.
- D. Nuclear membrane and nucleoli form.
Correct answer: A
Rationale: During anaphase, the sister chromatids, joined at the centromere, separate and move towards opposite ends of the spindle apparatus. This movement ensures that each daughter cell receives an identical set of chromosomes. Choice B is incorrect as the disintegration of the nuclear membrane and nucleoli occurs during prophase. Choice C is incorrect as chromatids align at the center of the spindle during metaphase, not anaphase. Choice D is incorrect as the formation of the nuclear membrane and nucleoli occurs during telophase, not anaphase.
4. How is the plasma membrane arranged?
- A. In a single layer made of proteins
- B. In a double layer made of proteins
- C. In a single layer of phospholipids
- D. In a double layer of phospholipids
Correct answer: D
Rationale: The plasma membrane is arranged in a double layer of phospholipids, known as a phospholipid bilayer. This structure consists of two layers of phospholipid molecules with hydrophilic heads facing the exterior and hydrophobic tails facing the interior, providing a semipermeable barrier for the cell. Choice A is incorrect because the plasma membrane is not made of a single layer of proteins. Choice B is incorrect as the double layer is composed of phospholipids, not proteins. Choice C is incorrect as the plasma membrane is not made of a single layer of phospholipids but rather a double layer.
5. Which organelle is responsible for organizing protein synthesis?
- A. Nucleus
- B. Ribosome
- C. Lysosome
- D. Vacuole
Correct answer: B
Rationale: The correct answer is B: Ribosome. Ribosomes are responsible for organizing protein synthesis by assembling amino acids. They are the cellular machinery where proteins are synthesized. The other choices, such as the nucleus, lysosome, and vacuole, do not directly participate in protein synthesis. The nucleus contains DNA and controls cell activities, the lysosome is involved in digestion and waste removal, and the vacuole is responsible for storage and maintaining cell turgor pressure.
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