HESI A2
HESI A2 Biology Practice Test 2024
1. How many pairs of chromosomes do all humans have?
- A. 24 pairs
- B. 23 pairs
- C. 22 pairs
- D. 20 pairs
Correct answer: B
Rationale: All humans have 23 pairs of chromosomes, totaling 46 chromosomes. Choice A is incorrect because humans do not have 24 pairs. Choice C is incorrect as humans have 23 pairs, not 22 pairs. Choice D is incorrect as humans have 23 pairs of chromosomes, not 20 pairs.
2. 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.
3. Which statement regarding energy content is true?
- A. Decomposers < secondary consumers
- B. Primary consumers < producers
- C. Producers > secondary consumers
- D. Secondary consumers < primary consumers
Correct answer: C
Rationale: The correct answer is C: "Producers > secondary consumers." Producers, like plants, are the foundation of the energy pyramid, containing the highest energy content in an ecosystem. They convert solar energy into chemical energy through photosynthesis. Secondary consumers, being organisms that feed on other organisms, have lower energy content compared to producers. This hierarchy in energy content is due to the transfer of energy through trophic levels. Choice A is incorrect because decomposers, though essential for nutrient recycling, typically have lower energy content than secondary consumers. Choice B is incorrect because primary consumers, which feed directly on producers, have lower energy content than producers. Choice D is incorrect because secondary consumers have lower energy content compared to primary consumers.
4. Which part of cellular respiration produces the greatest amount of ATP?
- A. electron transport chain
- B. glycolysis
- C. citric acid cycle
- D. fermentation
Correct answer: A
Rationale: The electron transport chain (ETC) produces the greatest amount of ATP during cellular respiration. This process occurs in the inner mitochondrial membrane and involves the transfer of electrons through a series of protein complexes, creating a proton gradient that drives the synthesis of ATP. By utilizing the energy from the electron carriers NADH and FADH2 produced in earlier stages of cellular respiration, the ETC can generate a large amount of ATP efficiently through oxidative phosphorylation. Glycolysis only produces a small amount of ATP in comparison to the ETC. The citric acid cycle generates some ATP but not as much as the ETC. Fermentation does not produce ATP through oxidative phosphorylation and yields a much smaller amount of ATP compared to the ETC.
5. In an example of a male with hemophilia and a female carrier, what ratio of the offspring are predicted neither to carry nor to manifest the disease?
- A. 0 females : 1 male
- B. 1 female : 1 male
- C. 1 female : 0 males
- D. 2 females : 1 male
Correct answer: D
Rationale: In this scenario, the male offspring will inherit the Y chromosome from the father and the X chromosome from the carrier mother. As a result, they will not have the hemophilia gene. The female offspring will inherit one X chromosome from the mother, which does not carry the hemophilia gene, and one X chromosome from the father, which does not exist due to the Y chromosome. Therefore, all female offspring will not carry or manifest hemophilia, resulting in a ratio of 2 females to 1 male. Choice A is incorrect because it does not account for the female offspring. Choices B and C are incorrect as they do not reflect the correct ratio based on the inheritance pattern of hemophilia.
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