HESI A2
Biology HESI A2 2024
1. Physical factors such as temperature and pH can alter enzyme activity because they have an effect on the enzyme's ___________.
- A. acidity
- B. shape
- C. chemistry
- D. substrate
Correct answer: B
Rationale: Physical factors such as temperature and pH can alter enzyme activity by affecting the enzyme's shape. Enzymes rely on their specific shapes to function properly and catalyze reactions. Any changes in temperature or pH can disrupt these shapes, causing the enzyme to become denatured and lose its functionality. Therefore, alterations in temperature and pH can impact enzyme activity by directly affecting their shapes. Choices A, C, and D are incorrect because while pH can affect acidity and chemical properties of the enzyme, and temperature can influence the enzyme-substrate interaction, the primary reason for enzyme activity alteration due to temperature and pH is the change in the enzyme's shape.
2. How do animal cells divide?
- A. Through a contractile ring
- B. Via a cell plate
- C. Both methods
- D. None of the above
Correct answer: A
Rationale: Animal cells divide through a contractile ring made of actin and myosin filaments. The ring contracts, pinching the cell membrane in the middle to form two daughter cells. Plant cells use a cell plate due to their rigid cell walls, making choices B and C incorrect. Choice D is incorrect as animal cells do use the contractile ring method for division.
3. Which statement is true of enzymes?
- A. They are made from lipids.
- B. They are made from proteins.
- C. They form double chains of DNA.
- D. They bind with catalysts.
Correct answer: B
Rationale: The correct answer is B: Enzymes are made from proteins. Enzymes are biological molecules that act as catalysts to speed up chemical reactions in living organisms. While the majority of enzymes are proteins, a few are made from RNA. The statement that enzymes are made from lipids (choice A) is incorrect. Enzymes do not form double chains of DNA (choice C) as their primary function is not related to DNA structure. Additionally, enzymes themselves do not bind with catalysts (choice D); instead, they act as catalysts to facilitate reactions.
4. 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.
5. Which of the following is not a function of the skeletal system?
- A. Providing the shape and form of our bodies
- B. Supporting and protecting the body
- C. Producing blood
- D. Storing vitamins
Correct answer: C
Rationale: Producing blood is not a function of the skeletal system. Blood production primarily occurs in the bone marrow, which is found within the bones. The skeletal system provides the shape and form of our bodies, supports and protects the body, and stores minerals like calcium and phosphorus for various functions. Storing vitamins is not a primary function of the skeletal system, although some vitamins may play a role in bone health.
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