HESI RN
Biology Practice Test
1. Which of the following is responsible for the synthesis of carbohydrates, lipids, and steroid hormones?
- A. Smooth endoplasmic reticulum (ER)
- B. Rough endoplasmic reticulum (ER)
- C. Golgi apparatus
- D. Ribosomes
Correct answer: A
Rationale: The smooth endoplasmic reticulum (ER) is the correct answer. It is responsible for the synthesis of lipids, including steroids, and also plays a role in carbohydrate metabolism. The rough endoplasmic reticulum (ER) is involved in protein synthesis and processing, not lipid or carbohydrate synthesis. The Golgi apparatus is responsible for modifying, sorting, and packaging of proteins and lipids, but not for their synthesis. Ribosomes are the cellular organelles responsible for protein synthesis, not lipid or carbohydrate synthesis.
2. What is the composition of the cellular membrane?
- A. A bilayer of phospholipid molecules
- B. A single layer of phospholipid molecules
- C. Proteins that act as transport highways
- D. Carbohydrates
Correct answer: A
Rationale: The cellular membrane is primarily composed of a phospholipid bilayer, which consists of two layers of phospholipid molecules. These molecules have a hydrophilic (water-attracting) head and hydrophobic (water-repelling) tail, creating a barrier that separates the internal cellular environment from the external surroundings. While proteins are embedded within this bilayer and act as transport channels, receptors, and structural support, carbohydrates are found on the outer surface of the membrane for cell recognition and signaling purposes. Therefore, the correct answer is a bilayer of phospholipid molecules.
3. What is the difference between saturated and unsaturated fatty acids?
- A. There is no difference between saturated and unsaturated fatty acids.
- B. Saturated fatty acids contain double bonds, unlike unsaturated fatty acids.
- C. Saturated fatty acids often contain two or more pairs of double bonds, unlike unsaturated fatty acids.
- D. Saturated fatty acids contain no double bonds, unlike unsaturated fatty acids.
Correct answer: D
Rationale: The correct answer is D. Saturated fatty acids contain no double bonds between the carbon atoms in their hydrocarbon chains, making them more solid at room temperature. Choice A is incorrect because there is a significant difference between saturated and unsaturated fatty acids. Choice B is incorrect as it inaccurately states that saturated fatty acids contain double bonds, which is a property of unsaturated fatty acids. Choice C is also incorrect as saturated fatty acids do not contain double bonds, let alone two or more pairs of double bonds.
4. What percentage of the parents' offspring is predicted to have a cleft chin if one parent carries the recessive gene for a cleft chin (c) while the other parent does not?
- A. 25%
- B. 50%
- C. 0%
- D. 75%
Correct answer: C
Rationale: The correct answer is C (0%). If one parent carries the recessive gene for a cleft chin while the other parent does not carry it, none of their offspring is predicted to have a cleft chin. This is because the cleft chin trait is recessive, so for an offspring to express this trait, they would need to inherit the gene from both parents. In this scenario, none of the offspring will inherit the recessive gene from both parents, so the percentage of offspring predicted to have a cleft chin is 0%. Choices A, B, and D are incorrect because in this situation, the offspring will not express the cleft chin phenotype, although they could be carriers of the recessive gene.
5. Which of the following organelles is known as the cell's digestion center?
- A. Chloroplasts
- B. Mitochondria
- C. Lysosomes
- D. Ribosomes
Correct answer: C
Rationale: The correct answer is C: Lysosomes. Lysosomes contain enzymes that break down waste materials and cellular debris within the cell, making them the cell's digestion center. Choice A, Chloroplasts, are responsible for photosynthesis. Choice B, Mitochondria, are the powerhouse of the cell, generating energy. Choice D, Ribosomes, are involved in protein synthesis. Therefore, Lysosomes are specifically known for their role in digestion within the cell.
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