why is polarity the most important characteristic of water
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HESI A2

HESI A2 Biology Practice Test

1. Why is polarity the most important characteristic of water?

Correct answer: A

Rationale: Polarity is the most important characteristic of water because it results in hydrogen bonding, a high specific heat value, and its versatile solvent properties. These unique properties enable water to form hydrogen bonds with other substances, resist temperature changes, and dissolve a wide variety of solutes, making it essential for life processes. Choice B is incorrect because water exhibits hydrogen bonding, not covalent bonding. Choice C is incorrect as water does not form ionic bonds. Choice D is incorrect because water has a high, not low, specific heat value, which is vital for its role in temperature regulation.

2. Which, if any, of the following statements are true?

Correct answer: D

Rationale: Both statements A and C are true. Water indeed boils at approximately 100°C (212°F) at standard atmospheric pressure. However, water boils at a lower temperature in areas of lower pressure due to the decreased atmospheric pressure, which affects the vapor pressure and boiling point of water. Statement B is incorrect because the boiling point is the temperature at which the vapor pressure equals the external pressure (atmospheric pressure in this case), not when it is higher.

3. How many chromosomes do sperm and egg produce in meiosis?

Correct answer: B

Rationale: Sperm and egg cells undergo meiosis to form gametes with half the number of chromosomes found in somatic cells. Each sperm and egg cell produces 23 chromosomes through meiosis. Choice A is incorrect because 46 chromosomes represent the diploid number found in somatic cells. Choice C is incorrect as it is an uncommon number for chromosome production in human gametes. Choice D is incorrect as the total number of chromosomes in sperm or egg cells is 23, not 24.

4. Which of the following is false?

Correct answer: B

Rationale: The statement "B. Animal cells use chloroplasts to gain energy" is false. Chloroplasts are only present in plant cells and certain algae, where they are responsible for photosynthesis to generate energy from sunlight. Animal cells rely on other organelles, such as mitochondria, for energy production. Choice A is true because animal cells use lysosomes to break down old cells and cellular waste. Choice C is true as plant cells have a cell wall composed of cellulose that provides structural support and protection.

5. Which of the following is not true about enzymes?

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.

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