HESI A2
HESI A2 Biology 2024
1. A student was asked to count birds in a given location over a 24-hour period. Which count would make their data most valid?
- A. Count birds at one feeder every 6 hours.
- B. Count birds at three feeders at noon and 6:00 P.M.
- C. Count birds at one feeder at noon and 6:00 P.M.
- D. Count birds at three feeders every 6 hours.
Correct answer: C
Rationale: Counting birds at one feeder at consistent time intervals (noon and 6:00 P.M.) over a 24-hour period ensures that the data collected are evenly distributed and provide a more accurate representation of the bird population in that location throughout the day. This method allows for observations during different times of the day, capturing potential variations in bird activity and distribution. Choice A is not as effective as it lacks observations at different times of the day, potentially missing variations in bird behavior. Choice B involves multiple locations and times, which could introduce more variables and make it harder to analyze the data accurately. Choice D, counting birds at three feeders every 6 hours, may provide too frequent data points and not cover all significant time intervals for observing bird activity.
2. What organelle in the cell produces energy through the process of respiration?
- A. Nucleus
- B. Mitochondria
- C. Golgi Apparatus
- D. Chloroplasts
Correct answer: B
Rationale: The correct answer is B: Mitochondria. The mitochondria are known as the powerhouse of the cell and are responsible for producing energy through respiration in eukaryotic cells. Choice A, the Nucleus, is not involved in energy production but rather houses the cell's genetic material. Choice C, the Golgi Apparatus, is responsible for packaging and processing proteins, not energy production. Choice D, Chloroplasts, are responsible for photosynthesis in plant cells, not respiration for energy production.
3. Which of the following describes how a bacterium reproduces?
- A. Mitosis
- B. Meiosis
- C. Binary fission
- D. Cytokinesis
Correct answer: C
Rationale: Bacteria reproduce through a process called 'binary fission.' During binary fission, a bacterium duplicates its DNA and then divides into two identical daughter cells. This method is the primary way bacteria replicate. Choice A, 'Mitosis,' is incorrect because mitosis is a process specific to eukaryotic cells, where the nucleus divides to produce two identical nuclei. Choice B, 'Meiosis,' is incorrect as meiosis is a specialized type of cell division that produces gametes with half the chromosome number. Choice D, 'Cytokinesis,' is not the correct answer as cytokinesis is the physical process of cell division, which occurs after the genetic material has been divided in mitosis or meiosis.
4. Which of the following organelles is responsible for producing ATP in cells?
- A. Nucleus
- B. Mitochondrion
- C. Chloroplast
- D. Lysosome
Correct answer: B
Rationale: The correct answer is 'Mitochondrion.' Mitochondria are known as the powerhouse of the cell and are responsible for producing ATP, the energy currency of the cell. The nucleus is responsible for storing genetic material and controlling cell activities, not for ATP production. Chloroplasts are found in plant cells and are responsible for photosynthesis, not ATP production. Lysosomes are involved in digestion and waste removal, not ATP production.
5. Which type of passive transport uses proteins that change shape to move a target molecule through the membrane?
- A. Diffusion
- B. Carrier proteins
- C. Channel proteins
- D. None of the above
Correct answer: B
Rationale: The correct answer is B: Carrier proteins. Carrier proteins are involved in facilitated diffusion, a type of passive transport where specific target molecules are moved across the membrane with the help of proteins that change shape. These carrier proteins bind to the target molecule on one side of the membrane, undergo a conformational change, and then release the molecule on the other side. This process is crucial for the selective transport of certain molecules that cannot pass through the membrane by simple diffusion. Choices A and C are incorrect because diffusion and channel proteins do not involve proteins that change shape to transport target molecules selectively. Choice D is incorrect as carrier proteins fit the description provided in the question.
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