HESI A2
HESI A2 Biology Practice Test 2024
1. Where is the genetic code for each person stored?
- A. RNA
- B. DNA
- C. Nucleus
- D. Chromosomes
Correct answer: B
Rationale: The genetic code for each person is stored in DNA. DNA carries all the hereditary information, including unique traits and characteristics. RNA (Choice A) is involved in protein synthesis but does not hold the complete genetic code. The nucleus (Choice C) is a cellular organelle that houses the DNA, but it is not the genetic code itself. Chromosomes (Choice D) are structures made of DNA and proteins, but the genetic code is specifically encoded in the DNA molecule.
2. Three students measured the mass of a product of combustion. They recorded measurements of 14 g, 16 g, and 17 g. If the known mass of the product is 30 g, how would you describe the students’ measurements?
- A. Accurate
- B. Precise
- C. Both accurate and precise
- D. Neither accurate nor precise
Correct answer: B
Rationale: The students' measurements are precise because they are consistently close to each other. However, they are not accurate because all the measurements deviate from the known mass of the product (30 g). Accuracy refers to how close a measurement is to the true or accepted value, while precision refers to the level of agreement among repeated measurements. Since the students' measurements are consistent but do not align with the true value, they can be considered precise but not accurate. Choice A is incorrect because accuracy relates to the proximity of the measurements to the true value, which is not the case here. Choice C is incorrect because although the measurements are precise, they are not accurate. Choice D is incorrect because the measurements are precise as they show good agreement with each other, even though they are not accurate.
3. Which structure controls the passage of substances into and out of the cell?
- A. Vacuole
- B. Cell Membrane
- C. Nuclear Membrane
- D. Cytoplasm
Correct answer: B
Rationale: The correct answer is the Cell Membrane. The cell membrane acts as a barrier that controls the passage of substances into and out of the cell. It is selectively permeable, allowing only certain molecules to pass through. Vacuole (Choice A), Nuclear Membrane (Choice C), and Cytoplasm (Choice D) do not primarily regulate the passage of substances in and out of the cell. Vacuoles are responsible for storage, the nuclear membrane surrounds the nucleus providing protection, and the cytoplasm is the fluid where organelles are suspended.
4. Which of the following are considered the most important molecules in biology?
- A. Carbohydrates, lipids, protein, and nucleic acids
- B. Carbohydrates, lipids, protein, and calcium
- C. Carbohydrates, lipids, protein, and sulfur
- D. Carbohydrates, lipids, protein, and iron
Correct answer: A
Rationale: The correct answer is A: Carbohydrates, lipids, protein, and nucleic acids are considered the most important molecules in biology. Carbohydrates are essential for providing energy, lipids for storing energy and forming cell membranes, proteins for various structural and functional roles, and nucleic acids (DNA and RNA) for storing genetic information. Choices B, C, and D are incorrect because while carbohydrates, lipids, and proteins are crucial biomolecules, calcium, sulfur, and iron are not considered among the most important molecules in biology.
5. 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.
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