HESI A2
Biology HESI A2 2024
1. Why is yeast used to make bread rise?
- A. It engages in photosynthesis, which produces oxygen gas.
- B. Carbon dioxide forms while yeast carries out photosynthesis.
- C. Yeast carries out fermentation, producing ethanol and carbon dioxide.
- D. Yeast breathes in oxygen and produces carbon dioxide through aerobic respiration.
Correct answer: C
Rationale: Yeast is used to make bread rise because it carries out fermentation, producing carbon dioxide gas. The carbon dioxide gas gets trapped in the dough, causing it to rise and create a fluffy texture in the bread. Choices A, B, and D are incorrect because yeast does not engage in photosynthesis, so it does not produce oxygen gas, does not carry out photosynthesis to form carbon dioxide, and does not produce carbon dioxide through aerobic respiration. Yeast's fermentation process is essential for bread rising.
2. What does the passage on Bridge imply about playing the game?
- A. Playing bridge requires concentration.
- B. Bridge is only for older people.
- C. Bridge is extremely easy to learn.
- D. Bridge is too hard for beginners to learn.
Correct answer: A
Rationale: The passage implies that playing bridge requires concentration, focus, and mental effort. It mentions that Bridge can be complicated for beginners but with time, effort, and a good teacher, even novices can become proficient. The description of the game's components, such as bidding and playing, highlights the need for the player's undivided attention. The passage doesn't suggest that Bridge is exclusively for older people (B), extremely easy to learn (C), or too hard for beginners to learn (D).
3. How does an enzyme work on a chemical reaction that occurs in a substrate?
- A. An enzyme slows down the chemical reaction.
- B. An enzyme speeds up the chemical reaction.
- C. An enzyme has no effect on the chemical reaction.
- D. An enzyme stops most chemical reactions.
Correct answer: B
Rationale: Enzymes are biological catalysts that facilitate chemical reactions by lowering the activation energy required for the reaction to occur. This allows the reaction to proceed more quickly and efficiently. Enzymes do not change the overall outcome of the reaction, but they significantly increase the rate at which it takes place. Therefore, choice B, 'An enzyme speeds up the chemical reaction,' is the correct answer. Choices A, C, and D are incorrect because enzymes do not slow down, have no effect, or stop chemical reactions; instead, they accelerate the process by lowering the activation energy.
4. What is the crystalline compound that is a product of protein metabolism known as?
- A. uracil
- B. urine
- C. ureter
- D. urea
Correct answer: D
Rationale: Urea is the correct answer. It is the crystalline compound formed in the liver from the breakdown of proteins, a byproduct of protein metabolism. Urea is excreted by the kidneys in the form of urine, aiding in the elimination of nitrogenous waste from the body. Uracil (Choice A) is a nitrogenous base found in RNA, not a product of protein metabolism. Urine (Choice B) is the liquid waste excreted by the kidneys but not the crystalline compound resulting from protein metabolism. Ureter (Choice C) is a duct that carries urine from the kidneys to the bladder, not the compound produced from protein metabolism.
5. Which conclusion can be drawn from Ohm’s law?
- A. Voltage and current are inversely proportional when resistance is constant.
- B. The ratio of the potential difference between the ends of a conductor to current is a constant, R.
- C. Voltage is the amount of charge that passes through a point per second.
- D. Power (P) can be calculated by multiplying current (I) by voltage (V).
Correct answer: B
Rationale: Ohm's law states that the ratio of the potential difference (voltage) between the ends of a conductor to the current flowing through it is a constant. Mathematically, this is represented as V = I x R, where V is voltage, I is current, and R is the constant resistance. Therefore, the correct conclusion that can be drawn from Ohm's law is that the ratio of the potential difference between the ends of a conductor to current is a constant, denoted as R. This relationship is fundamental to understanding the behavior of electrical circuits and the effect of resistance on voltage and current. Choice A is incorrect because Ohm's law actually states that voltage and current are directly proportional when resistance is constant. Choice C is incorrect because voltage is not the amount of charge that passes through a point per second; rather, it is the electric potential energy per unit charge. Choice D is incorrect because although power (P) can be calculated by multiplying current (I) by voltage (V), this is not a conclusion directly drawn from Ohm's law.
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