HESI A2
Biology HESI A2 Practice Test
1. Enzymes can _ reactions.
- A. Catalyze
- B. Inhibit
- C. Stop
- D. None of the above
Correct answer: A
Rationale: Enzymes function as catalysts that promote and accelerate chemical reactions in biological systems. They do this by lowering the activation energy required for the reactions to occur, thereby speeding up the process without being consumed in the reaction. Enzymes facilitate reactions rather than inhibiting or stopping them. Therefore, the correct answer is 'Catalyze.' 'Inhibit' and 'Stop' are incorrect because enzymes do not hinder or halt reactions but rather enhance them.
2. Why is homeostasis necessary?
- A. It maintains temperature
- B. It maintains pH
- C. It maintains glucose levels
- D. All of the above
Correct answer: D
Rationale: Homeostasis is necessary because it ensures the maintenance of a stable, relatively constant internal environment. This includes regulating various factors such as temperature, pH levels, and glucose levels to support optimal bodily functions and overall health. Choices A, B, and C are all correct as they represent key aspects of homeostasis that contribute to maintaining the body's internal balance.
3. Which type of sugar is a disaccharide?
- A. Sucrose
- B. Fructose
- C. Glucose
- D. Galactose
Correct answer: A
Rationale: The correct answer is A, Sucrose. Sucrose is a disaccharide composed of one molecule of glucose and one molecule of fructose. When glucose and fructose combine, they form sucrose. Choice B, Fructose, is a monosaccharide, not a disaccharide. Choice C, Glucose, is also a monosaccharide, not a disaccharide. Choice D, Galactose, is another monosaccharide and not a disaccharide.
4. In order, from lower to upper, the layers of the atmosphere are:
- A. Exosphere, thermosphere, mesosphere, stratosphere, troposphere
- B. Troposphere, stratosphere, mesosphere, thermosphere, exosphere
- C. Mesosphere, troposphere, stratosphere, thermosphere, exosphere
- D. Thermosphere, troposphere, stratosphere, mesosphere, exosphere
Correct answer: B
Rationale: The correct order of the layers of the atmosphere, from lower to upper, is troposphere, stratosphere, mesosphere, thermosphere, exosphere. The troposphere is the lowest layer where weather phenomena occur. The stratosphere contains the ozone layer, which absorbs and scatters the solar ultraviolet radiation. The mesosphere is where most meteorites burn up upon entering the Earth's atmosphere. The thermosphere is characterized by high temperatures due to the absorption of solar radiation. The exosphere is the outermost layer where the atmosphere transitions into space. Therefore, option B is the correct sequence, as it reflects the ascending order of the Earth's atmospheric layers.
5. Which of the following is false?
- A. Animal cells use lysosomes to break down old cells
- B. Animal cells use chloroplasts to gain energy
- C. Plant cells have a cell wall to maintain structure
- D. All of the above are true
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.
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