HESI A2 Biology Practice Test

Try our free HESI A2 Biology practice test. This is an interactive exam with instant scoring and detailed explanations. There are 40 HESI Biology practice questions to work through. These are challenging questions that cover all of the key concepts that you must know for this exam. Read each question and then choose the best answer. Click on the arrow in the lower right corner to move on to the next question.

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Question 1
Which of the following is a correct description of metaphase during mitosis?

A
The nuclear envelope disappears and the chromosomes begin to attach to the spindle that forms along the axis of the cell.
B
Chromosomes gather on either side of the now separating cell.
C
Chromosomes start to separate.
D
Chromosomes align along the center of the cell.
Question 1 Explanation: 
During metaphase, the chromosomes align along the center of the cell. During prometaphase the nuclear envelope disappears and the chromosomes start to attach to the spindle. Anaphase is when the chromosomes start to separate. Telophase is when the chromosomes gather on either side of the now separating cell; it leads into cytokinesis in animal cells.
Question 2
Where can ribosomes be found inside a cell?

A
Attached to the endoplasmic reticulum and in the cytoplasm.
B
Only in the cytoplasm.
C
Only attached to the endoplasmic reticulum.
D
None of the above.
Question 2 Explanation: 
Ribosomes can be found in two places: attached to the endoplasmic reticulum (Rough ER) or free floating in the cytoplasm.
Question 3
What is the role of the Golgi apparatus in the cell?

A
To provide intracellular digestion.
B
To provide transportation of materials throughout the cell.
C
To uptake food through the cell membrane.
D
To produce cellular respiration.
Question 3 Explanation: 
The Golgi apparatus is responsible for transport of materials throughout the cell. Intracellular digestion occurs within lysosomes, while food uptake is the job of vacuoles. Cellular respiration is the function of mitochondria.
Question 4
What characteristic of water allows for hydrogen bonding between molecules?

A
Its high specific heat.
B
Its cohesive properties.
C
Its covalent bonds.
D
Its polar nature.
Question 4 Explanation: 
Although all the other characteristics about water are true, water’s polar nature is what allows for hydrogen bonding between molecules.
Question 5
Which of the following is the MOST inclusive in the hierarchic system of organization?

A
Kingdom.
B
Class.
C
Genus.
D
Species.
Question 5 Explanation: 
The most inclusive classification is Kingdom, which includes all forms of life on earth. The most EXCLUSIVE would be Species. The mnemonic “King Philip Came Over For Great Spaghetti,” can be used to recall the order of the system from most inclusive to least inclusive.
Question 6
In which phase of the cell cycle is DNA replicated?

A
G1
B
S
C
G2
D
D1
Question 6 Explanation: 
The G1, S, and G2 phases are called interphase. S phase is when DNA is replicated. (G1 = growth phase, G2 = second growth phase and preparation for division). There is no such thing as the D1 phase.
Question 7
Which of the following processes reduces cells originally classified as diploid to haploid?

A
Meiosis.
B
Mitosis.
C
Both meiosis and mitosis.
D
Neither meiosis and mitosis.
Question 7 Explanation: 
Meiosis is a process of cellular division where cells begin as diploid and end as haploid.
Question 8
Which of the following is an example of a cell created by meiosis?

A
Kidney cell.
B
Sperm cell.
C
Brain cell.
D
Skin cell.
Question 8 Explanation: 
Sperm contain 23 chromosomes that are combined with another 23 from an egg to produce a diploid combination. Meiosis replicates sex, or sperm, cells and mitosis replicates somatic, or body, cells.
Question 9
The Krebs cycle is a process described as:

A
the creation of ATP and Pyruvate.
B
the creation of GTP and NADH.
C
the process by which plants take in carbon dioxide and produce oxygen.
D
a linear method of creating energy.
Question 9 Explanation: 
This description is the most correct. The Krebs cycle involves creating energy in the form of 2 GTPs (which convert to ATP) and NADH (and FAHD2 which donate the electrons to the ETC), not harvesting it, and it is not only used by plants. In addition, it is cyclical, not linear. ATP and Pyruvate are created by glycolysis.
Question 10
The plasma membranes of cells are composed of:

A
a single layer of phospholipid molecules.
B
a bilayer of phospholipid molecules.
C
proteins that act as transport highways.
D
mitochondria.
Question 10 Explanation: 
Plasma membranes are composed of a bilayer of phospholipid molecules.
Question 11
Which of the following activities does NOT lead to cellular energy production?

A
Glycolysis.
B
Gluconeogenesis.
C
Oxidative Phosphorylation.
D
Cellular Respiration.
Question 11 Explanation: 
Cellular respiration leads to glycolysis while Oxidative Phosphorylation (a type of cellular respiration), and both create energy by catabolism. Gluconeogenesis is the creation of sugar using energy.
Question 12
Using garden peas, which of the following scientists discovered the basic principles of genetics?

A
Galileo.
B
Mendel.
C
Curie.
D
Hawking.
Question 12 Explanation: 
Gregor Mendel discovered, through careful experimentation with garden peas, that there existed genetic properties to account for certain characteristics.
Question 13
The alternative versions of a single gene are known as:

A
traits.
B
characteristics.
C
RNA.
D
alleles.
Question 13 Explanation: 
Alleles are alternative versions of a single gene that codes for a certain trait.
Question 14
What device makes it possible to predict the genotype and phenotype of the offspring of sexual reproduction?

A
Punnett square.
B
Chi square.
C
PCR.
D
Microscope.
Question 14 Explanation: 
A Punnett square makes it possible to predict the genotype/phenotype by listing alleles and their various possible combinations and likelihoods.
Question 15
The traits which an organism shows (as opposed to what its genes code for), is known by which of the following terms?

A
Phenotype.
B
Genotype.
C
Stereotype.
D
Classification.
Question 15 Explanation: 
The phenotype of an organism is a demonstration of the genes expressed, rather than what they actually code for (genotype). Phenotype can be remembered as the physical characteristics of an organism.
Question 16
An organism that has a genotype of two dominant alleles for one gene is:

A
Heterozygous.
B
Homozygous.
C
Multiparous.
D
Nulliparous.
Question 16 Explanation: 
When an organism possesses the same type of alleles for one gene, it is homozygous. The prefix homo- indicates same, and the prefix hetero- indicates different.
Question 17
The method by which mRNA is created is begun by which of the following processes?

A
Replication.
B
Translation.
C
Splitting.
D
Transcription.
Question 17 Explanation: 
Transcription is the first step in the creation of mRNA from a strand of DNA.
Question 18
Which scientists are responsible for describing the structure of DNA?

A
Watson and Crick.
B
Watson and Holmes.
C
Holmes and Croiger.
D
Brown and Curie.
Question 18 Explanation: 
Francis Crick and James D. Watson are the scientists responsible for describing the double helix structure of DNA.
Question 19
All genes can be described using the Punnett Square method. True or False?

A
True
B
False
Question 19 Explanation: 
False. There are many more complicated forms of genetic expression available than the simple genetics represented by the Punnett Square.
Question 20
The term pleiotropy is best defined as:

A
A condition in which multiple genes are missing.
B
A situation in which one gene remains unexpressed.
C
One gene influencing multiple, seemingly unrelated phenotypic traits.
D
Two genes affected by a single allele.
Question 20 Explanation: 
Pleiotropy describes conditions where one gene has multiple effects on phenotypic traits. The prefix pleio- means “many,” or “more,” and –tropy means “way.”
Question 21
Which molecules are responsible for the base pairing action in DNA?

A
Phosphate groups.
B
Sugar molecules.
C
Nitrogenous bases.
D
Codons.
Question 21 Explanation: 
Base pairs are formed by hydrogen bonds between the nitrogenous bases (ATGC) while the sugar and phosphate make up the ‘back bone’.
Question 22
Glycolysis is the conversion of _______ to ______ in the process of cellular respiration.

A
Glucose, pyruvate.
B
Pyruvate, glucose.
C
NADH, pyruvate.
D
NADH, ATP.
Question 22 Explanation: 
Glycolysis is the conversion of glucose to pyruvate and is the first step in the process of cellular respiration.
Question 23
The oxidation of the NADH molecules to produce oxygen and water in cellular respiration takes place in a series of steps defined as:

A
Cellular inspiration.
B
Krebs cycle.
C
Electron transport chain.
D
Cellular conversion.
Question 23 Explanation: 
The electron transport chain oxidizes NADH molecules to produce oxygen and finally to produce water.
Question 24
For every glucose molecule utilized during cellular respiration, approximately how many ATP molecules can be produced?

A
14 to 18.
B
18 to 25.
C
32 to 36.
D
68 to 70.
Question 24 Explanation: 
Cellular respiration can generate from 32 to 36 molecules of ATP for every single glucose molecule broken down. The number of ATP is described as a range because the reaction is not perfect and will sometimes yield more or less ATP.
Question 25
Cells with a high rate of protein synthesis generally have a large number of which of the following cellular structures?

A
Mitochondria.
B
Ribosomes.
C
Lysosomes.
D
Golgi apparati.
Question 25 Explanation: 
Ribosomes aid in protein synthesis. Therefore, cells with a high rate of protein synthesis tend to have a large number of ribosomes.
Question 26
A scientist is proposing an experiment to study the effect of a certain chemical on rat brain development. The scientist believes that this chemical will enhance the rats’ brain development. Which of the following terms describes this step of the scientific process?

A
Hypothesis.
B
Experiment.
C
Analysis.
D
Conclusion.
Question 26 Explanation: 
The scientist has formed a hypothesis, a statement of certain events or happenings, and is ready to conduct his experiment. Analysis is not a step in the scientific method.
Question 27
Which of the following is a correct description of the shape of frozen water molecules?

A
Ladder.
B
Block.
C
Parallel.
D
Lattice.
Question 27 Explanation: 
When frozen, water molecules form a lattice structure. This is the reason that ice appears to “expand” in comparison to water.
Question 28
What is the difference between saturated and unsaturated fatty acids?

A
Saturated fatty acids contain double bonds, unlike unsaturated fatty acids.
B
Saturated fatty acids contain no double bonds, unlike unsaturated fatty acids.
C
Saturated fatty acids often contain two or more pairs of double bonds, unlike unsaturated fatty acids.
D
There is no difference between saturated and unsaturated fatty acids.
Question 28 Explanation: 
Saturated fatty acids contain no double bonds, while unsaturated fatty acids do contain double bonds.
Question 29
Diets that contain high amounts of saturated fatty acids are linked to what disease type?

A
Renal.
B
Coronal.
C
Cardiovascular.
D
Pleural.
Question 29 Explanation: 
Diets containing high amounts of saturated fatty acids have been linked to cardiovascular problems. Cardiovascular refers to the heart and blood vessels.
Question 30
Based on the inherent properties of water molecules, what effect would a large body of water have on the temperature of a climate?

A
Increase.
B
Decrease.
C
Stabilize.
D
Destabilize.
Question 30 Explanation: 
A large body of water will have a stabilizing effect on a climate due to its high specific heat property.
Question 31
Which of the following descriptions relates to water’s property of cohesion?

A
Water beading together on top of a freshly waxed car.
B
An ocean stabilizing the temperature of a region.
C
Water dissolving salt to become salt water.
D
A bottle of water cracking when left in the freezer.
Question 31 Explanation: 
Cohesion describes the tendency of molecules of the same substance to bond together, as is demonstrated in water beading. An ocean stabilizing local temperature refers to water’s high specific heat. Water dissolving salt to become saltwater refers to its potent solvent ability. The bottle of water that cracks after being left in the freezer is an example of the expansion of water during freezing due to its lattice structure.
Question 32
In DNA, adenosine will only bond with which of the following base pairs?

A
Adenosine.
B
Thymine.
C
Guanine.
D
Uracil.
Question 32 Explanation: 
Adenosine will only bond with thymine, and guanine will only bond with cytosine. Adenosine will bind to Uracil only in RNA. Cardiovascular refers to the heart and blood vessels. A useful mnemonic device for recalling not only the base pairings, but also whether the nucleotide is a purine or a pyrimidine is “GCAT PuPy PuPy” for DNA, and “GCAU PuPy PuPy” for RNA. This method links G to C, and A to T or U, while G and A are described as purines and C, T, and U are described as pyrimidines.
Question 33
A pea plant has alleles for the dominant tall gene (T) and the recessive short gene (t). Therefore, it appears as Tt. Which of the following will correctly describe its phenotype if there is complete dominance? And which describes incomplete dominance? (complete, incomplete)

A
Tall, Tall
B
Average. Tall
C
Tall, Average
D
Tall, Short
Question 33 Explanation: 
Because the dominant allele is present, this pea plant will be tall despite its recessive gene in complete dominance. In Incomplete dominance however, the gene must be homozygous to show one trait. Otherwise the phenotype will be a mixture of the two alleles.
Question 34
What is the function of tRNA during DNA transcription?

A
tRNA bonds together amino acids and then releases them to create an elongated chain of amino acids.
B
tRNA contains codons during DNA transcription.
C
tRNA is the piece of DNA produced during transcription.
D
tRNA brings the amino acids to the site of synthesis.
Question 34 Explanation: 
tRNA brings the amino acids to the site of protein synthesis. Ribosomes bond together amino acids and then release them to create an elongated chain of amino acids. tRNA contains anticodons, not codons, and mRNA is the new piece of DNA produced.
Question 35
The liver is an organ responsible for detoxifying the body of many harmful substances. Therefore, you might expect the liver to contain a high amount of:

A
Rough endoplasmic reticulum.
B
Lysosomes.
C
Mitochondria.
D
Smooth endoplasmic reticulum.
Question 35 Explanation: 
Smooth endoplasmic reticulum has a large function in detoxifying and metabolizing many molecules.
Question 36
A scientist conducts an experiment to discover the effect of music on plant growth. He hypothesizes that the music will help plants grow at a faster rate than plants without music. By the end of the experiment, plants grown with music playing grew to an average height of 5.6 inches, while plants grown without music playing grew to an average height of 2.3 inches. Which of the following is the scientist’s correct conclusion?

A
All plants grow better with music.
B
In the experiment, plants grown with music grew better than those grown without it.
C
In the experiment, plants grown without music grew better than those grown without it.
D
All plants grow better without music.
Question 36 Explanation: 
This is the correct conclusion to draw from this experiment. “All plants” is too general a term. The data supports the conclusion that music aided growth.
Question 37
It is known that the gene that codes for male pattern baldness depends on the gene for red hair. This type of interaction between alleles is known as:

A
Interplay.
B
Affectation.
C
Genotype.
D
Epistasis.
Question 37 Explanation: 
Epistasis is the interaction between two alleles which have different effects in combination than individually.
Question 38
What is the function of the stomach?

A
Absorption of nutrients
B
Digestion of Nutrients
C
Digestion and Absorption of nutrients
D
None of the above.
Question 38 Explanation: 
The stomach is the site of storage and digestion. It does NOT absorb any nutrients. Absorption occurs mostly in the small intestine.
Question 39
What is the largest type of biological molecule?

A
Lipid.
B
Protein.
C
Carbohydrate.
D
Steroid.
Question 39 Explanation: 
Protein molecules are the largest type of biological molecules.
Question 40
Phagocytes in the immune system are responsible for the biological action of:

A
Secreting.
B
Consuming.
C
Altering.
D
Building.
Question 40 Explanation: 
Phagocytes consume smaller biological organisms. 'Phagocytosis' is the act of surrounding or consuming. For example, in the immune system, phagocytes surround and digest invaders.
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