HESI A2 › § Biology
Free HESI A2 Biology Practice Questions
The HESI A2 biology subtest asks 25 scored questions in 25 minutes, covering cell structure and function, metabolism, genetics, and body systems at a molecular level. It moves fast, one question per minute, so recognising a concept quickly matters as much as knowing it.
The seven questions below are original, written by RedRubric and mapped to the same outline as the full HESI A2 biology bank. Each one comes with a rationale explaining why the correct answer is correct and why the others are not, so you leave knowing more than your score.
A laboratory places red blood cells into a saline solution that has a higher solute concentration than the fluid inside the cells. What happens to the red blood cells as a result of osmosis?
Select an answer to reveal the explanation.
Correct answer: D, Water moves out of the cells and into the surrounding solution, causing the cells to shrink
Osmosis is the net movement of water through a membrane that lets water pass but restricts solutes, and that water always travels toward whichever side is more concentrated in solute. Because the solution surrounding the cells here is more concentrated than the fluid inside them, water exits the cells into the solution and the cells shrink. Red blood cell membranes are freely permeable to water, so option a is incorrect.
Using a codon table where AUG codes for methionine, UGC codes for cysteine, CAU codes for histidine, and UAG signals stop, what is the correct amino acid sequence produced by the mRNA strand AUG-UGC-CAU-UAG?
Select an answer to reveal the explanation.
Correct answer: D, Methionine, cysteine, histidine, then the chain ends
Reading the strand three bases at a time in order, AUG codes for methionine, UGC codes for cysteine, and CAU codes for histidine. UAG is a stop codon, not an amino acid, so the ribosome releases the finished three amino acid chain there rather than adding a fourth amino acid or reordering the sequence.
A patient's blood carbon dioxide level rises. Chemoreceptors detect the change and trigger an increase in the rate and depth of breathing. Why does this count as negative feedback?
Select an answer to reveal the explanation.
Correct answer: B, Because the response works to lower carbon dioxide back toward its set point, opposing the original rise
Negative feedback is defined by the response opposing the stimulus; increased breathing expels excess carbon dioxide, driving the level back down toward the set point.
A breeder crosses a true breeding red snapdragon with a true breeding white snapdragon, and every offspring in the next generation has pink flowers rather than red or white. Which inheritance pattern does this best illustrate?
Select an answer to reveal the explanation.
Correct answer: B, Incomplete dominance, where the heterozygote shows a blended phenotype
A single blended phenotype in every heterozygous offspring, pink rather than red or white patches, is the signature of incomplete dominance rather than codominance or simple dominance.
A researcher tests whether a new IV catheter dressing lowers infection rates. One group of patients receives the new dressing. A second group, matched for age, catheter type, and insertion site, receives the standard dressing instead. Infection rate after 72 hours is recorded for both groups. What is the second group of patients called in this experiment?
Select an answer to reveal the explanation.
Correct answer: D, The control group
The control group is treated identically to the experimental group except for the one factor being tested, which here is the dressing type, so the standard dressing group is the control. The experimental group is the one receiving the new dressing being tested, not the standard one. The independent variable is the dressing type itself, and the dependent variable is the infection rate being measured, neither of which is a group of patients.
A patient recovers fully from a viral infection. Months later, exposure to the identical virus produces no noticeable illness at all. What explains this outcome?
Select an answer to reveal the explanation.
Correct answer: D, Memory B and T cells from the first infection recognise the pathogen and mount a faster, stronger response
Memory B cells and T cells persist after an infection clears and can recognise the same antigen much faster on a later exposure, mounting a response quick and strong enough to prevent noticeable illness. The innate immune system stays non-specific and does not adapt to one particular pathogen, neutrophils are not lymphocytes and do not carry antigen-specific memory, and the virus itself does not change based on a prior host's immune response.
A human skin cell with 46 chromosomes completes mitosis and cytokinesis. How many chromosomes does each resulting daughter cell contain, and why?
Select an answer to reveal the explanation.
Correct answer: D, 46, because mitosis divides duplicated chromosomes evenly, keeping the chromosome number constant from parent to daughter cells
Mitosis splits sister chromatids evenly between two daughter nuclei, so each daughter cell finishes with a chromosome count matching the parent cell it came from, 46 in a human somatic cell. Cutting that number to 23 is meiosis's job, not mitosis's, and sister chromatids separate during anaphase rather than remaining attached, so neither 92 nor a later recombining step is correct.
That is seven of hundreds.
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Practise all HESI A2 biologyquestions →What the HESI biology subtest covers, and how many questions.
What’s on the HESI A2 biology subtest
The HESI A2 Biology subtest is 30 questions in 25 minutes, of which 25 are scored. It spans 5 content areas.
- Foundations of Biology. Start with the scientific method, the chemistry of water, and homeostasis.
- Cell Biology. Learn the organelles, how the membrane moves things, and how cells make energy.
- Cell Division and Genetics. Follow mitosis and meiosis, then predict inheritance with Punnett squares.
- Molecular Biology. See how DNA copies itself and how a gene becomes a protein.
- Microbiology and Immunity. Meet the pathogens that cause disease and the immune system that answers them.
What students ask about HESI biology.
HESI A2 biology questions, answered.
How many questions are on the HESI A2 biology subtest?
The biology subtest has 25 scored questions with a 25 minute time limit. Some test centres add a small number of unscored pilot questions that look identical to scored ones, so treat every question as counting.
Are these real HESI A2 questions?
No. Every question here is original, written by RedRubric and checked against the published HESI A2 biology outline. We do not reproduce Elsevier's questions, and Elsevier has not reviewed or endorsed this practice set.
Is seven questions enough to know if I am ready?
Not on its own. Seven questions show you the format and the rationale style, but a 25 question timed subtest and a full length mock are what actually tell you whether your pace and recall hold up under pressure. Use the free set to decide whether the full bank is worth your time, then test properly.