HESI A2
HESI A2 Biology 2024
1. What are saturated fats saturated with?
- A. Hydrogen atoms
- B. Carbon atoms
- C. Oxygen atoms
- D. Nitrogen atoms
Correct answer: A
Rationale: Saturated fats are saturated with hydrogen atoms. This means that each carbon atom in the fatty acid chains forming saturated fats is bonded to as many hydrogen atoms as possible. This saturation results in the fatty acid chains being straight and closely packed together, making saturated fats solid at room temperature. Choice B (Carbon atoms), C (Oxygen atoms), and D (Nitrogen atoms) are incorrect because saturated fats are specifically saturated with hydrogen atoms, not carbon, oxygen, or nitrogen atoms.
2. How should a researcher test the hypothesis that radiation from cell phones is significant enough to raise the temperature of water in a test tube?
- A. Dial a cell phone that rests beside a test tube of water, let it ring for two minutes, and record the temperature of the water before and after the two-minute interval.
- B. Dial a cell phone that rests beside a test tube of water; let it ring for two, three, and four minutes; and record the temperature of the water before and after each interval.
- C. Use three different brands of cell phone; dial each as it rests beside its own test tube of water, let it ring for two minutes, and record the temperature of the water before and after the two-minute interval.
- D. Use three different brands of cell phone, dial each and let one ring for two minutes, one for three minutes, and one for four minutes; record the temperature of the water before and after each interval.
Correct answer: A
Rationale: To test the hypothesis that radiation from cell phones raises the temperature of water in a test tube, the most appropriate method is to dial a cell phone next to a test tube of water, let it ring for a consistent two-minute interval, and record the temperature before and after. Choice A is correct because it provides a controlled approach to isolate the impact of the phone's radiation on the water temperature. Choices B, C, and D introduce additional variables that could confound the results. Choice B varies the duration of exposure, making it difficult to attribute temperature changes specifically to the radiation. Choice C introduces the factor of different cell phone brands, which could introduce variability not related to radiation. Choice D also varies exposure times and introduces the factor of multiple phone brands, making it harder to determine the direct impact of cell phone radiation on water temperature. Therefore, choice A is the most suitable option for this experiment.
3. Which names a final step in protein synthesis?
- A. DNA unzips.
- B. Amino acids bond.
- C. Transfer RNA bonds to messenger RNA.
- D. Messenger RNA moves to ribosomes.
Correct answer: B
Rationale: The final step in protein synthesis is when amino acids bond together to form a protein chain. This process occurs during translation, where transfer RNA (tRNA) brings specific amino acids to the ribosome, and the ribosome catalyzes the formation of peptide bonds between the amino acids. This step ultimately leads to the synthesis of a complete protein based on the instructions from messenger RNA (mRNA). Choice A ('DNA unzips') is incorrect as it refers to the initiation of transcription, not the final step of protein synthesis. Choice C ('Transfer RNA bonds to messenger RNA') is incorrect as it describes the process of translation initiation rather than the final step. Choice D ('Messenger RNA moves to ribosomes') is also incorrect as mRNA is already present at the ribosomes throughout the translation process, not just in the final step.
4. Which color of light is least effective at driving photosynthesis?
- A. Violet
- B. Green
- C. Orange
- D. Red
Correct answer: B
Rationale: Green light is the least effective at driving photosynthesis because chlorophyll, the primary pigment responsible for absorbing light in plants, does not absorb green light well. Instead, chlorophyll absorbs more effectively in the blue and red regions of the light spectrum. Therefore, green light is relatively less efficient in promoting photosynthesis compared to violet, orange, and red light. Violet light, although at the shorter wavelength end of the spectrum, can still drive photosynthesis better than green light. Orange and red light are more efficiently absorbed by chlorophyll, making them more effective in driving the process of photosynthesis.
5. Which is a byproduct of fermentation in muscle cells?
- A. Ethanol
- B. Pyruvic acid
- C. Lactic acid
- D. Oxygen
Correct answer: C
Rationale: Lactic acid is a byproduct of fermentation in muscle cells. During intense exercise or when oxygen is limited, muscle cells use anaerobic respiration to generate energy. This process breaks down glucose into lactic acid, which can cause muscle fatigue and soreness. Choice A, Ethanol, is not produced in muscle cells during fermentation. Choice B, Pyruvic acid, is an intermediate product in glucose metabolism but is not a byproduct of fermentation in muscle cells. Choice D, Oxygen, is not a byproduct of fermentation but a reactant in aerobic respiration.
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