BIO 151 – General Biology I Practice Exam
2026/2027 Practice Questions & Study Guide |
Complete Exam-Style Questions with Correct
Detailed Answers & Rationales (Reliable
Answers)
Question 1
Which property of water is most directly responsible for the ability of water to moderate changes in
temperature in living organisms?
A. Its low density as a solid
B. Its ability to dissolve nonpolar molecules
C. Its high specific heat capacity
D. Its tendency to form ionic bonds
Correct Answer: C. Its high specific heat capacity
Water has a high specific heat capacity because hydrogen bonding between water molecules requires
substantial energy to disrupt. As a result, water can absorb or release considerable amounts of heat
while undergoing relatively small changes in temperature. This property helps organisms maintain
relatively stable internal temperatures and also contributes to the temperature stability of aquatic
environments. Water's low density as a solid and its solvent properties are important biological
characteristics, but they do not directly explain its resistance to temperature change.
Question 2
A scientist observes a cell containing a nucleus, mitochondria, endoplasmic reticulum, and Golgi
apparatus. Which conclusion is most appropriate?
A. The cell is definitely prokaryotic.
B. The cell is eukaryotic.
C. The cell must be a bacterial cell.
D. The cell cannot contain DNA.
,Correct Answer: B. The cell is eukaryotic.
The presence of a membrane-bound nucleus and membrane-bound organelles such as mitochondria,
endoplasmic reticulum, and the Golgi apparatus identifies the cell as eukaryotic. Prokaryotic cells do not
possess a membrane-bound nucleus or the extensive membrane-bound organelle system characteristic
of eukaryotic cells. Both prokaryotes and eukaryotes contain DNA, so the presence of DNA does not
distinguish the two groups.
Question 3
Which interaction is primarily responsible for stabilizing the secondary structure of a protein?
A. Peptide bonds between amino acids
B. Hydrogen bonds along the polypeptide backbone
C. Ionic bonds between phosphate groups
D. Glycosidic bonds between amino acids
Correct Answer: B. Hydrogen bonds along the polypeptide backbone
Protein secondary structures, particularly alpha helices and beta-pleated sheets, are stabilized primarily
by hydrogen bonds between atoms in the polypeptide backbone. Peptide bonds link amino acids together
and therefore establish the primary structure. Interactions involving side chains contribute substantially
to tertiary and quaternary structure, but they are not the primary force responsible for secondary
structure.
Question 4
A red blood cell is placed in a solution that has a lower solute concentration than the cell's cytoplasm.
What is most likely to happen?
A. Water will leave the cell, causing it to shrink.
B. Water will enter the cell, causing it to swell.
C. Solutes will move out until the cell becomes isotonic.
D. No net movement of water will occur.
Correct Answer: B. Water will enter the cell, causing it to swell.
The external solution is hypotonic relative to the cell because it has a lower solute concentration. Water
moves across a selectively permeable membrane toward the region with the higher effective solute
concentration. Therefore, water enters the red blood cell. Because animal cells lack a rigid cell wall,
excessive water entry can cause the cell to swell and potentially lyse.
,Question 5
Which organelle is primarily responsible for modifying, sorting, and packaging proteins that have been
synthesized in the rough endoplasmic reticulum?
A. Lysosome
B. Nucleolus
C. Golgi apparatus
D. Peroxisome
Correct Answer: C. Golgi apparatus
The Golgi apparatus receives proteins and lipids from the endoplasmic reticulum and modifies, sorts, and
packages them for delivery to various cellular destinations. Lysosomes contain digestive enzymes, the
nucleolus is involved in ribosome production, and peroxisomes participate in processes such as fatty acid
oxidation and detoxification.
Question 6
Which statement best describes an enzyme's role in a biochemical reaction?
A. It changes the equilibrium constant of the reaction.
B. It increases the activation energy required for the reaction.
C. It lowers the activation energy required for the reaction.
D. It permanently changes into the product of the reaction.
Correct Answer: C. It lowers the activation energy required for the reaction.
Enzymes function as biological catalysts by lowering the activation energy required for a reaction. They
do not change the overall free-energy difference between reactants and products or alter the equilibrium
position of a reaction. Enzymes participate in reactions without being permanently consumed, allowing
them to be reused.
Question 7
A competitive inhibitor reduces enzyme activity by binding to the enzyme's active site. Which change
would most directly reduce the inhibitor's effect?
A. Increasing the concentration of substrate
B. Decreasing the concentration of enzyme
C. Removing all cofactors
D. Lowering the temperature to near freezing
, Correct Answer: A. Increasing the concentration of substrate
Competitive inhibitors compete with the substrate for access to the enzyme's active site. Increasing
substrate concentration makes it more likely that substrate molecules will bind to the active site instead
of inhibitor molecules. This type of inhibition can therefore often be reduced by increasing substrate
concentration. Noncompetitive inhibition behaves differently because the inhibitor binds at a site other
than the active site.
Question 8
Which molecule is the immediate energy currency most commonly used to power cellular work?
A. DNA
B. ATP
C. Glucose
D. NADPH
Correct Answer: B. ATP
ATP, or adenosine triphosphate, is the primary immediate energy-transfer molecule used by cells.
Hydrolysis of ATP can release usable free energy that drives processes such as active transport,
mechanical work, and biosynthetic reactions. Glucose stores substantial chemical energy, but it is not the
cell's immediate energy currency in the same sense as ATP.
Question 9
During cellular respiration, most ATP generated from one molecule of glucose is produced during which
process?
A. Glycolysis
B. The citric acid cycle
C. Oxidative phosphorylation
D. Fermentation
Correct Answer: C. Oxidative phosphorylation
Most ATP produced during aerobic cellular respiration is generated by oxidative phosphorylation.
Electrons carried by NADH and FADH2 move through the electron transport chain, allowing energy to
pump protons across the inner mitochondrial membrane. The resulting proton gradient drives ATP
synthase to produce ATP. Glycolysis and the citric acid cycle generate ATP directly, but their direct ATP
yields are much smaller.
2026/2027 Practice Questions & Study Guide |
Complete Exam-Style Questions with Correct
Detailed Answers & Rationales (Reliable
Answers)
Question 1
Which property of water is most directly responsible for the ability of water to moderate changes in
temperature in living organisms?
A. Its low density as a solid
B. Its ability to dissolve nonpolar molecules
C. Its high specific heat capacity
D. Its tendency to form ionic bonds
Correct Answer: C. Its high specific heat capacity
Water has a high specific heat capacity because hydrogen bonding between water molecules requires
substantial energy to disrupt. As a result, water can absorb or release considerable amounts of heat
while undergoing relatively small changes in temperature. This property helps organisms maintain
relatively stable internal temperatures and also contributes to the temperature stability of aquatic
environments. Water's low density as a solid and its solvent properties are important biological
characteristics, but they do not directly explain its resistance to temperature change.
Question 2
A scientist observes a cell containing a nucleus, mitochondria, endoplasmic reticulum, and Golgi
apparatus. Which conclusion is most appropriate?
A. The cell is definitely prokaryotic.
B. The cell is eukaryotic.
C. The cell must be a bacterial cell.
D. The cell cannot contain DNA.
,Correct Answer: B. The cell is eukaryotic.
The presence of a membrane-bound nucleus and membrane-bound organelles such as mitochondria,
endoplasmic reticulum, and the Golgi apparatus identifies the cell as eukaryotic. Prokaryotic cells do not
possess a membrane-bound nucleus or the extensive membrane-bound organelle system characteristic
of eukaryotic cells. Both prokaryotes and eukaryotes contain DNA, so the presence of DNA does not
distinguish the two groups.
Question 3
Which interaction is primarily responsible for stabilizing the secondary structure of a protein?
A. Peptide bonds between amino acids
B. Hydrogen bonds along the polypeptide backbone
C. Ionic bonds between phosphate groups
D. Glycosidic bonds between amino acids
Correct Answer: B. Hydrogen bonds along the polypeptide backbone
Protein secondary structures, particularly alpha helices and beta-pleated sheets, are stabilized primarily
by hydrogen bonds between atoms in the polypeptide backbone. Peptide bonds link amino acids together
and therefore establish the primary structure. Interactions involving side chains contribute substantially
to tertiary and quaternary structure, but they are not the primary force responsible for secondary
structure.
Question 4
A red blood cell is placed in a solution that has a lower solute concentration than the cell's cytoplasm.
What is most likely to happen?
A. Water will leave the cell, causing it to shrink.
B. Water will enter the cell, causing it to swell.
C. Solutes will move out until the cell becomes isotonic.
D. No net movement of water will occur.
Correct Answer: B. Water will enter the cell, causing it to swell.
The external solution is hypotonic relative to the cell because it has a lower solute concentration. Water
moves across a selectively permeable membrane toward the region with the higher effective solute
concentration. Therefore, water enters the red blood cell. Because animal cells lack a rigid cell wall,
excessive water entry can cause the cell to swell and potentially lyse.
,Question 5
Which organelle is primarily responsible for modifying, sorting, and packaging proteins that have been
synthesized in the rough endoplasmic reticulum?
A. Lysosome
B. Nucleolus
C. Golgi apparatus
D. Peroxisome
Correct Answer: C. Golgi apparatus
The Golgi apparatus receives proteins and lipids from the endoplasmic reticulum and modifies, sorts, and
packages them for delivery to various cellular destinations. Lysosomes contain digestive enzymes, the
nucleolus is involved in ribosome production, and peroxisomes participate in processes such as fatty acid
oxidation and detoxification.
Question 6
Which statement best describes an enzyme's role in a biochemical reaction?
A. It changes the equilibrium constant of the reaction.
B. It increases the activation energy required for the reaction.
C. It lowers the activation energy required for the reaction.
D. It permanently changes into the product of the reaction.
Correct Answer: C. It lowers the activation energy required for the reaction.
Enzymes function as biological catalysts by lowering the activation energy required for a reaction. They
do not change the overall free-energy difference between reactants and products or alter the equilibrium
position of a reaction. Enzymes participate in reactions without being permanently consumed, allowing
them to be reused.
Question 7
A competitive inhibitor reduces enzyme activity by binding to the enzyme's active site. Which change
would most directly reduce the inhibitor's effect?
A. Increasing the concentration of substrate
B. Decreasing the concentration of enzyme
C. Removing all cofactors
D. Lowering the temperature to near freezing
, Correct Answer: A. Increasing the concentration of substrate
Competitive inhibitors compete with the substrate for access to the enzyme's active site. Increasing
substrate concentration makes it more likely that substrate molecules will bind to the active site instead
of inhibitor molecules. This type of inhibition can therefore often be reduced by increasing substrate
concentration. Noncompetitive inhibition behaves differently because the inhibitor binds at a site other
than the active site.
Question 8
Which molecule is the immediate energy currency most commonly used to power cellular work?
A. DNA
B. ATP
C. Glucose
D. NADPH
Correct Answer: B. ATP
ATP, or adenosine triphosphate, is the primary immediate energy-transfer molecule used by cells.
Hydrolysis of ATP can release usable free energy that drives processes such as active transport,
mechanical work, and biosynthetic reactions. Glucose stores substantial chemical energy, but it is not the
cell's immediate energy currency in the same sense as ATP.
Question 9
During cellular respiration, most ATP generated from one molecule of glucose is produced during which
process?
A. Glycolysis
B. The citric acid cycle
C. Oxidative phosphorylation
D. Fermentation
Correct Answer: C. Oxidative phosphorylation
Most ATP produced during aerobic cellular respiration is generated by oxidative phosphorylation.
Electrons carried by NADH and FADH2 move through the electron transport chain, allowing energy to
pump protons across the inner mitochondrial membrane. The resulting proton gradient drives ATP
synthase to produce ATP. Glycolysis and the citric acid cycle generate ATP directly, but their direct ATP
yields are much smaller.
