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HESI A2 Biology practice questions

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These are original practice items written to the HESI A2 blueprint (4 options, no penalty for wrong answers), not actual exam questions. Try each one before you open the answer.

What this topic covers

Biology sits inside the Biology section of the HESI A2. Our bank holds 38 verified items tagged to it, and the 4 below are a fixed sample so the page stays the same every time you open it. Each one shows the reasoning, not just the letter.

The topic tag comes from our own items rather than from a published syllabus, so treat it as a map of what we cover. For the official section breakdown see the HESI A2 page.

Biology sample questions

Question 1

In a species of flower, red petal color (R) is incompletely dominant over white (r). A heterozygous plant (Rr) produces pink flowers. If a pink-flowered plant is crossed with a white-flowered plant, what percentage of the offspring will have pink flowers?

  1. A 25%
  2. B 50%
  3. C 0%
  4. D 100%
Show the answer and explanation

Correct answer: B

Cross Rr (pink) × rr (white). The pink parent passes R or r with equal chance, and the white parent always passes r, so the offspring are 50% Rr (pink) and 50% rr (white).

Why the other options are wrong:
A: 25% is the share of red (RR) or white (rr) offspring in an Rr × Rr cross; this cross makes half Rr.
C: 0% pink would require that no offspring receive R, as in rr × rr; the pink parent carries R.
D: 100% pink would require every offspring to be Rr, as in RR × rr; here half the offspring are rr.

Question 2

Which organelle is primarily responsible for producing ATP through oxidative phosphorylation?

  1. A Mitochondrion
  2. B Golgi apparatus
  3. C Ribosome
  4. D Nucleus
Show the answer and explanation

Correct answer: A

Mitochondria are known as the powerhouses of the cell because they generate most of the cell's ATP via oxidative phosphorylation in the inner membrane.

Why the other options are wrong:
B: The Golgi apparatus modifies, sorts, and packages proteins, but does not produce ATP.
C: Ribosomes synthesize proteins, not ATP.
D: The nucleus stores genetic material and directs cell activities, but does not produce ATP.

Question 3

Which of the following is the primary function of the mitochondria?

  1. A ATP production.
  2. B Lipid storage.
  3. C Protein synthesis.
  4. D DNA replication.
Show the answer and explanation

Correct answer: A

Mitochondria are known as the powerhouses of the cell because they generate most of the cell's supply of adenosine triphosphate (ATP), the main energy currency. This is their primary function.

Why the other options are wrong:
B: Lipid storage is associated with organelles like lipid droplets or adipose tissue, not mitochondria.
C: Protein synthesis occurs primarily on ribosomes, not in mitochondria.
D: DNA replication occurs in the nucleus (and mitochondria have their own DNA, but replication is not their primary cellular function).

Question 4

Which organelle is responsible for modifying, sorting, and packaging proteins for secretion?

  1. A Golgi apparatus
  2. B rough ER
  3. C ribosome
  4. D lysosome
Show the answer and explanation

Correct answer: A

The Golgi apparatus modifies, sorts, and packages proteins from the ER into vesicles for transport to other destinations, including secretion.

Why the other options are wrong:
B: The rough ER has ribosomes and synthesizes proteins, but modification and packaging occur in the Golgi.
C: Ribosomes synthesize proteins but do not modify or package them.
D: Lysosomes contain digestive enzymes and break down materials; they are not involved in packaging for secretion.

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