HESI A2
Biology HESI A2 Practice Exam
1. Which of the following are found both in open and closed circulatory systems?
- A. Arteries
 - B. Red blood cells
 - C. Capillaries
 - D. Immune cells
 
Correct answer: C
Rationale: The correct answer is C, Capillaries. Capillaries are found in both open and closed circulatory systems. Capillaries are small blood vessels that connect arteries and veins, allowing for the exchange of nutrients and wastes between the blood and tissues. They are essential components of circulatory systems regardless of whether they are open or closed. Arteries (Choice A) are not found in open circulatory systems, as these systems lack distinct arteries and veins. Red blood cells (Choice B) are present in the blood but are not exclusive to either open or closed circulatory systems. Immune cells (Choice D) are not specific components of circulatory systems, as they are part of the immune system.
2. How are molecules of water bonded to each other?
- A. Ionic
 - B. Covalent
 - C. Hydrogen
 - D. Molecular
 
Correct answer: C
Rationale: Water molecules are bonded to each other by 'hydrogen' bonds. These bonds are not as strong as covalent bonds, which hold the atoms within each water molecule together (Choice B). Ionic bonds (Choice A) involve the transfer of electrons between atoms, which is not the case in water molecules. The term 'molecular' (Choice D) is too general and doesn't specifically describe the type of bond between water molecules.
3. Which of the following is not true about enzymes?
- A. They catalyze reactions
 - B. They lower the activation energy needed
 - C. They have an active site
 - D. They are typically proteins
 
Correct answer: B
Rationale: Enzymes lower the activation energy needed for a reaction to occur, not raise it. By lowering the activation energy, enzymes facilitate reactions, making them occur more easily and rapidly. Choice A is correct as enzymes indeed catalyze reactions. Choice C is correct as enzymes have specific active sites where substrates bind. Choice D is correct as enzymes are commonly proteins, although some RNA molecules also exhibit catalytic properties.
4. How does asexual reproduction differ from sexual reproduction?
- A. asexual reproduction results in all cells being identical to the original cell; sexual reproduction results in half of the cells being identical to the original cell
 - B. asexual reproduction results in two cells that contribute genetic material to daughter cells, resulting in significantly greater variation
 - C. sexual reproduction involves two cells that contribute genetic material to daughter cells, resulting in significantly greater variation
 - D. sexual reproduction involves one cell that yields all cells produced to be identical
 
Correct answer: C
Rationale: Sexual reproduction involves two cells (gametes) that contribute genetic material to daughter cells, resulting in significantly greater genetic variation in the offspring. This genetic variation is essential for evolution and adaptation to environmental changes. In contrast, asexual reproduction involves one cell dividing to produce offspring that are genetically identical to the parent cell. Choice A is incorrect because sexual reproduction does not result in half of the cells being identical to the original cell; it involves two cells contributing genetic material. Choice B is incorrect because asexual reproduction does not result in significantly greater variation; it produces genetically identical offspring. Choice D is incorrect because sexual reproduction involves two cells contributing genetic material, not one cell yielding all identical cells.
5. During which phase of cell division do the chromosomes replicate?
- A. Prophase
 - B. Interphase
 - C. Anaphase
 - D. Telophase
 
Correct answer: B
Rationale: Chromosomes replicate during the interphase of the cell cycle. Interphase is the phase where the cell prepares for division by undergoing various activities such as growth, DNA replication, and protein synthesis. During DNA replication in interphase, each chromosome in the cell is duplicated to form two sister chromatids, which are then separated during cell division. Prophase is the phase where the chromosomes condense, and the nuclear envelope breaks down. Anaphase is the phase where sister chromatids are pulled apart towards opposite poles of the cell. Telophase is the phase where the nuclear envelope reforms, and chromosomes begin to decondense.
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