HESI A2
HESI A2 Biology 2024
1. 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.
2. Whose energy efficiency is greater?
- A. Herbivore
- B. Carnivore
- C. Omnivore
- D. Decomposer
Correct answer: D
Rationale: Decomposers have the greatest efficiency of energy among the given options. Decomposers break down organic matter, such as dead plants and animals, into simpler substances through the process of decomposition. This breakdown process results in the release of nutrients back into the ecosystem, making energy more readily available for other organisms to use. In contrast, herbivores, carnivores, and omnivores all derive their energy from the consumption of other living organisms, making their energy efficiency lower than that of decomposers. Herbivores consume plants for energy, which involves energy loss due to inefficiencies in converting plant matter into usable energy. Carnivores consume herbivores or other carnivores, leading to further energy loss through each trophic level. Omnivores consume both plant and animal matter, but their energy efficiency is still lower than decomposers because of the energy loss associated with consuming living organisms. Decomposers play a crucial role in recycling nutrients and energy in ecosystems, making them highly efficient in the utilization of energy.
3. What provides the cell with the ability to move and propel?
- A. Microfilaments
- B. Microtubules
- C. Flagella
- D. Cilia
Correct answer: B
Rationale: Microtubules are the cellular structures responsible for cell movement and propulsion. Microtubules are part of the cytoskeleton and play a crucial role in various cellular processes, including cell motility and intracellular transport. While microfilaments also contribute to cell movement by enabling muscle contraction and cell shape changes, they are not primarily responsible for propelling the cell. Flagella and cilia are cellular appendages involved in cell movement, but they are composed of microtubules, making them the structures that move due to the actions of microtubules.
4. Which part of the plant produces pollen?
- A. Anther
- B. Style
- C. Stigma
- D. Pistil
Correct answer: A
Rationale: The anther is the part of the flower that produces pollen. It is located at the tip of the stamen, the male reproductive organ of a flower. The anther contains pollen sacs where pollen grains are produced. The style is the part of the pistil that connects the stigma to the ovary, playing a role in pollen tube growth. The stigma is the part of the pistil that receives pollen during fertilization. The pistil is the female reproductive organ of a flower, consisting of the stigma, style, and ovary, and does not produce pollen.
5. Which of these is not an example of a lipid?
- A. Butter
- B. Wax
- C. Canola oil
- D. Honey
Correct answer: D
Rationale: Honey is not an example of a lipid because lipids are fat-related molecules that are insoluble in water, while honey is a natural sweet substance made by bees and primarily consists of sugars such as glucose and fructose. Butter, wax, and canola oil are examples of lipids as they are all composed of fat-related molecules that do not dissolve in water.
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