HESI A2 practice test

HESI A2 Biology Practice Test

Cells, genetics, metabolism and classification. Here are 10 HESI A2 biology questions, each with the answer and the reason.

Updated 2026-11-14 by the Tigertest team. Based on the HESI A2 section outlines (math, reading, vocabulary, grammar, biology, chemistry, anatomy and physiology). Physics is not included. Not affiliated with Elsevier.

1. 1.

   A student measures how tall bean plants grow when given different amounts of fertilizer. In this experiment, plant height is which type of variable?

   • A.

     Dependent variable

   • B.

     Independent variable

   • C.

     Controlled variable

   • D.

     Control group

   Answer: A.

   Plant height is what the student measures in response to the change, so it is the dependent variable. The amount of fertilizer is the independent variable because the student changes it on purpose.

2. 2.

   Proteins such as hemoglobin and insulin are polymers built from which type of monomer?

   • A.

     Monosaccharides

   • B.

     Nucleotides

   • C.

     Amino acids

   • D.

     Fatty acids

   Answer: C.

   Proteins are chains of amino acids joined by peptide bonds. Nucleotides are the monomers of nucleic acids, and monosaccharides are the monomers of carbohydrates.

3. 3.

   Which statement is one of the basic principles of the cell theory?

   • A.

     All cells come from preexisting cells

   • B.

     All cells contain a nucleus

   • C.

     All cells contain chloroplasts

   • D.

     Cells can arise from nonliving matter

   Answer: A.

   Cell theory states that all living things are made of cells, the cell is the basic unit of life, and all cells come from preexisting cells. Bacteria have no nucleus, so not all cells contain one.

4. 4.

   Which structure is found in plant cells but not in animal cells?

   • A.

     Mitochondrion

   • B.

     Cell membrane

   • C.

     Ribosome

   • D.

     Cell wall

   Answer: D.

   Plant cells have a rigid cellulose cell wall outside the cell membrane, along with chloroplasts, while animal cells have only the membrane. Both cell types contain mitochondria, so that option is wrong.

5. 5.

   The sodium-potassium pump moves sodium ions out of a nerve cell against their concentration gradient. Which process is this?

   • A.

     Simple diffusion

   • B.

     Active transport

   • C.

     Osmosis

   • D.

     Facilitated diffusion

   Answer: B.

   Moving a substance against its concentration gradient requires energy from ATP, which defines active transport. Facilitated diffusion uses a carrier protein but only moves substances down their gradient, with no energy cost.

6. 6.

   During a sprint, a runner's muscle cells run short of oxygen. Which substance builds up as the cells switch to anaerobic respiration?

   • A.

     Lactic acid

   • B.

     Ethanol

   • C.

     Carbon dioxide

   • D.

     Oxygen

   Answer: A.

   Without enough oxygen, human muscle cells use lactic acid fermentation so glycolysis can keep making a small amount of ATP, and lactic acid accumulates. Ethanol fermentation occurs in yeast, not in human cells.

7. 7.

   A sample of double-stranded DNA is 30% adenine. What percentage of its bases are guanine?

   • A.

     30%

   • B.

     70%

   • C.

     20%

   • D.

     40%

   Answer: C.

   Adenine pairs with thymine, so thymine is also 30%, leaving 40% for guanine and cytosine together. Guanine pairs with cytosine in equal amounts, so each is 20%.

8. 8.

   When a human skin cell divides by mitosis to repair a wound, what is the result?

   • A.

     Two genetically identical diploid cells

   • B.

     Four genetically different haploid cells

   • C.

     Two haploid gametes

   • D.

     Four identical diploid cells

   Answer: A.

   Mitosis produces two daughter cells that are diploid and genetically identical to the parent, which supports growth and tissue repair. Four genetically different haploid cells are the product of meiosis.

9. 9.

   A red snapdragon is crossed with a white snapdragon, and all of the offspring have pink flowers. This inheritance pattern is called:

   • A.

     Codominance

   • B.

     Sex-linked inheritance

   • C.

     Complete dominance

   • D.

     Incomplete dominance

   Answer: D.

   In incomplete dominance, the heterozygote shows a blended, intermediate phenotype such as pink. In codominance both traits appear fully side by side, as in type AB blood.

10. 10.

    In the scientific name Homo sapiens, the word Homo identifies which level of taxonomic classification?

    • A.

      Species

    • B.

      Genus

    • C.

      Family

    • D.

      Order

    Answer: B.

    Binomial nomenclature gives the genus (capitalized) followed by the species epithet (lowercase), so Homo is the genus. The species is named by both words together, Homo sapiens, not by Homo alone.