HESI A2
Biology HESI A2 Practice Test
1. Which is true of gametes?
- A. They are diploid cells
- B. They are haploid cells
- C. They are somatic
- D. A & C are true
Correct answer: B
Rationale: Gametes are sex cells (sperm and eggs) that are involved in sexual reproduction. They are haploid cells, meaning they have half the number of chromosomes (n) compared to diploid cells. This is necessary for the formation of a diploid zygote when two gametes unite during fertilization. Somatic cells are non-reproductive cells in the body, so they are not gametes. Choice A is incorrect because gametes are not diploid but haploid. Choice C is incorrect because gametes are not somatic cells.
2. What type of cells are involved in meiosis (sex cells)?
- A. Somatic Cells
- B. Gametes
- C. Zygote
- D. Diploid Cells
Correct answer: B
Rationale: The correct answer is B, Gametes. Gametes are the specialized sex cells involved in meiosis, such as sperm and eggs. Somatic cells (A) are non-reproductive cells found in the body, not involved in meiosis. Zygote (C) is the result of fertilization, formed when gametes unite. Diploid cells (D) have two sets of chromosomes, but in meiosis, gametes are produced through a process of cell division that reduces the chromosome number by half to haploid.
3. Which one of the following best describes the function of a cell membrane?
- A. It controls the substances entering and leaving the cell.
- B. It maintains the cell's shape.
- C. It controls the substances entering the cell.
- D. It supports the cell's structures.
Correct answer: A
Rationale: The correct answer is A. The function of a cell membrane is to control the substances entering and leaving the cell. The cell membrane is selectively permeable, allowing it to regulate the movement of ions and molecules in and out of the cell to maintain internal balance and proper function. Choice B is incorrect because while the cell membrane does provide some structural support, its primary function is not to maintain the cell's shape. Choice C is incorrect because the cell membrane controls both the substances entering and leaving the cell, not just those entering. Choice D is incorrect as the primary function of the cell membrane is not to support the cell's structures but to regulate the movement of substances.
4. Which of the following organelles is responsible for producing ATP in cells?
- A. Nucleus
- B. Mitochondrion
- C. Chloroplast
- D. Lysosome
Correct answer: B
Rationale: The correct answer is 'Mitochondrion.' Mitochondria are known as the powerhouse of the cell and are responsible for producing ATP, the energy currency of the cell. The nucleus is responsible for storing genetic material and controlling cell activities, not for ATP production. Chloroplasts are found in plant cells and are responsible for photosynthesis, not ATP production. Lysosomes are involved in digestion and waste removal, not ATP production.
5. Which two bases are purines?
- A. Adenine (A)
- B. Cytosine (C)
- C. Thymine (T)
- D. Guanine (G)
Correct answer: A
Rationale: Adenine (A) and guanine (G) are the two bases that are purines. Purines are characterized by a double-ring structure containing two carbon rings, distinguishing them from pyrimidines. Adenine and guanine are purines because they possess this unique double-ring structure. Therefore, choices A and D, adenine and guanine, respectively, are the correct answers. Choices B and C, cytosine and thymine, are pyrimidines and do not exhibit the double-ring structure characteristic of purines.
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