HESI A2
Biology HESI A2 Practice Exam
1. Which cells in the human body lack nuclei?
- A. Nerve cells
- B. Red blood cells
- C. Liver cells
- D. Connective tissue cells
Correct answer: B
Rationale: Red blood cells, also known as erythrocytes, lack nuclei in humans. This absence of a nucleus allows more space for hemoglobin, the protein responsible for carrying oxygen, making red blood cells efficient at their function of oxygen transport in the body. Nerve cells (Choice A), liver cells (Choice C), and connective tissue cells (Choice D) all possess nuclei as they require genetic material for their functions, such as cell signaling, protein synthesis, and structural support.
2. Which form of fermentation is used to produce beer?
- A. Lactic acid fermentation
- B. Acetic acid fermentation
- C. Propionic acid fermentation
- D. Ethyl alcohol fermentation
Correct answer: D
Rationale: The correct answer is D, Ethyl alcohol fermentation. During beer production, yeast metabolizes sugars in the wort to produce ethanol (ethyl alcohol) and carbon dioxide, which are responsible for the alcohol content and carbonation in beer. Choices A, B, and C are incorrect because lactic acid fermentation produces lactic acid, acetic acid fermentation produces acetic acid, and propionic acid fermentation produces propionic acid, none of which are used in the production of beer.
3. DNA bases include all but which of the following?
- A. Adenine
- B. Thymine
- C. Uracil
- D. Cytosine
Correct answer: C
Rationale: The correct answer is C: Uracil. Uracil is not a DNA base; it is a base found only in RNA. The four bases in DNA are Adenine, Thymine, Cytosine, and Guanine. Choice A, Adenine, is a correct DNA base. Choice B, Thymine, is a correct DNA base. Choice D, Cytosine, is a correct DNA base. Therefore, Uracil is the only incorrect choice among the options provided.
4. Which organelle would you expect to be present in a cell responsible for detoxifying multiple molecules?
- A. rough ER
- B. smooth ER
- C. lysosome
- D. Golgi apparatus
Correct answer: B
Rationale: The smooth endoplasmic reticulum (ER) is the organelle responsible for detoxifying multiple molecules in a cell. It contains enzymes that help break down toxins and drugs, making it an essential organelle for detoxification processes. The rough ER, lysosome, and Golgi apparatus do not play direct roles in detoxification. The rough ER is mainly involved in protein synthesis and transport. Lysosomes are responsible for digestion and recycling within the cell. The Golgi apparatus is involved in modifying, sorting, and packaging proteins for secretion or for use within the cell.
5. 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.
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