HESI A2
Biology HESI A2 2024
1. What takes place in a lysosome?
- A. Ribosomes are made.
- B. Food is produced.
- C. Water is stored.
- D. Food is digested.
Correct answer: D
Rationale: In a lysosome, food particles are digested through the action of enzymes. Lysosomes are membrane-bound organelles containing digestive enzymes that break down large molecules into smaller ones, allowing the cell to utilize the nutrients for energy and other processes. Choices A, B, and C are incorrect because ribosomes are not made in lysosomes, food is not produced in lysosomes, and lysosomes do not store water.
2. If both parents have polydactylism, what percentage of their offspring is predicted to manifest the anomaly?
- A. 25%
- B. 50%
- C. 75%
- D. 100%
Correct answer: B
Rationale: When both parents have polydactylism, they each possess at least one dominant allele for polydactylism. Through a Punnett square analysis, it can be determined that 50% of their offspring will inherit the dominant allele from both parents. This results in a 100% chance of manifesting the anomaly (2 out of 4 possibilities). Therefore, 50% of the offspring are predicted to manifest the anomaly. Choices A, C, and D are incorrect as they do not align with the principles of Mendelian genetics and Punnett square analysis.
3. How is the plasma membrane arranged?
- A. In a single layer made of proteins
- B. In a double layer made of proteins
- C. In a single layer of phospholipids
- D. In a double layer of phospholipids
Correct answer: D
Rationale: The plasma membrane is arranged in a double layer of phospholipids, known as a phospholipid bilayer. This structure consists of two layers of phospholipid molecules with hydrophilic heads facing the exterior and hydrophobic tails facing the interior, providing a semipermeable barrier for the cell. Choice A is incorrect because the plasma membrane is not made of a single layer of proteins. Choice B is incorrect as the double layer is composed of phospholipids, not proteins. Choice C is incorrect as the plasma membrane is not made of a single layer of phospholipids but rather a double layer.
4. In a strand of DNA, you would expect to see adenine paired with ___________.
- A. cytosine
- B. uracil
- C. thymine
- D. guanine
Correct answer: C
Rationale: In a strand of DNA, adenine always pairs with thymine through two hydrogen bonds. This pairing is a fundamental aspect of DNA structure, where adenine and thymine complement each other in the double helix. Choice A (cytosine) is incorrect because adenine does not pair with cytosine in DNA. Choice B (uracil) is incorrect as uracil is found in RNA, not DNA. Choice D (guanine) is incorrect as guanine pairs with cytosine, not adenine, in DNA.
5. Select the cell parts that are present in plant cells but not animal cells (there may be more than one answer):
- A. Cell membrane
- B. Cell wall
- C. Ribosome
- D. Chloroplast
Correct answer: B
Rationale: Plant cells have a cell wall (B) which provides structural support and protection for the cell, a feature that is not present in animal cells. The cell membrane (A) is found in both plant and animal cells. Ribosomes (C) are present in both types of cells and are responsible for protein synthesis. Chloroplasts (D) are unique to plant cells and are responsible for carrying out photosynthesis. Therefore, the correct answers are B and D because the cell wall and chloroplast are specific to plant cells, while the cell membrane and ribosomes are found in both plant and animal cells.
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