Nursing Elites

1. As cattle graze, cattle egrets consume the insects they stir up. This is an example of ___________.

• A. Mutualism
• B. Parasitism
• C. Commensalism
• D. Competition

Correct answer: C

Rationale: Commensalism is a relationship between two species in which one benefits without affecting the other species. In this scenario, the cattle egrets benefit from the insects stirred up by cattle while the cattle are not significantly impacted by the presence of the egrets. The egrets obtain food easily, and the cattle are neither harmed nor helped by the egrets' presence, making it an example of commensalism. Mutualism involves both species benefiting, parasitism involves one species benefiting at the expense of the other, and competition involves both species being negatively affected by their interactions, none of which apply to the relationship between cattle and cattle egrets in this context.

2. How do animal cells divide?

• A. Through a contractile ring
• B. Via a cell plate
• C. Both methods
• D. None of the above

Correct answer: A

Rationale: Animal cells divide through a contractile ring made of actin and myosin filaments. The ring contracts, pinching the cell membrane in the middle to form two daughter cells. Plant cells use a cell plate due to their rigid cell walls, making choices B and C incorrect. Choice D is incorrect as animal cells do use the contractile ring method for division.

3. Which component of the cell contributes to the protection, communication, and passage of substances into and out of the cell?

• A. Nucleus
• B. Cell membrane
• C. Endoplasmic reticulum
• D. Cytoplasm

Correct answer: B

Rationale: The correct answer is the cell membrane. The cell membrane is responsible for protecting the cell, facilitating communication with the external environment, and regulating the passage of substances into and out of the cell. The nucleus (Choice A) is the control center of the cell and houses the genetic material but is not primarily involved in these functions. The endoplasmic reticulum (Choice C) is involved in protein synthesis and lipid metabolism, not primarily in protection or communication. The cytoplasm (Choice D) is the gel-like substance that fills the cell but does not specifically contribute to protection, communication, or substance passage.

4. Which of the following is not true about enzymes?

• A. They catalyze reactions
• B. They lower the activation energy needed
• C. They have an active site
• D. They are typically proteins

Correct answer: B

Rationale: Enzymes lower the activation energy needed for a reaction to occur, not raise it. By lowering the activation energy, enzymes facilitate reactions, making them occur more easily and rapidly. Choice A is correct as enzymes indeed catalyze reactions. Choice C is correct as enzymes have specific active sites where substrates bind. Choice D is correct as enzymes are commonly proteins, although some RNA molecules also exhibit catalytic properties.

5. Which organelle is responsible for organizing protein synthesis?

• A. Nucleus
• B. Ribosome
• C. Lysosome
• D. Vacuole

Correct answer: B

Rationale: The correct answer is B: Ribosome. Ribosomes are responsible for organizing protein synthesis by assembling amino acids. They are the cellular machinery where proteins are synthesized. The other choices, such as the nucleus, lysosome, and vacuole, do not directly participate in protein synthesis. The nucleus contains DNA and controls cell activities, the lysosome is involved in digestion and waste removal, and the vacuole is responsible for storage and maintaining cell turgor pressure.

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