PCB 3023C / PCB3023C Exam 1: (Latest Update
2026 / 2027) Cell Biology | Questions & Answers |
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PCB 3023 Exam
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2026 / 2027 Academic Year
Q: A reaction occurs spontaneously only if the change in free energy (ΔG) is
Answer:
negative
Q: Which of the following are required for glycolysis to take place?
Answer:
NAD+, Pi, ADP, ATP
Q: The free-energy change, ΔG, for the chemical reaction A → B is 0 kJ/mole at 37°C when the
concentrations of A and B are 10 M and 0.1 M, respectively. What is the free-energy change for the
reaction when the concentrations of A and B are 0.01 M and 1 M, respectively?
Answer:
+23.76 kJ/mole
Q: Which part of the mitochondrion contains porins?
Answer:
outer membrane
Q: What is true of the organelles that produce ATP in eukaryotic animal cells?
Answer:
They evolved from bacteria engulfed by ancestral cells billions of years ago.
Q: Which of the following is true for eukaryotic cells?
Answer: - Fats are converted to acetyl CoA in the mitochondria; sugars are converted to acetyl CoA in the cytosol - Sugars are converted to acetyl CoA, but fats are not - Fats are converted to acetyl CoA, but sugars are not - Sugars and fats are both converted to acetyl CoA in the mitochondria - Sugars are converted to acetyl CoA in the mitochondria; fats are converted to acetyl CoA in the cytosol
Sugars and fats are both converted to acetyl CoA in the mitochondria.
Q: For some biosynthetic reactions, such as the synthesis of nucleic acids, the energy supplied by the
hydrolysis of ATP to ADP and Pi is insufficient to drive the reaction forward. How can such reactions
occur inside cells?
Answer:
ATP is hydrolyzed to AMP and Pi in two successive hydrolysis reactions.
Q: Which of the following statements are true of mitochondria?
Answer: - In plant cells, they are replaced by chloroplasts - Inside a cell, they are mobile, constantly changing shape and position - They contain an outer membrane, an inner membrane, and two internal compartments - They are similar in size and shape to bacteria - They contain their own DNA and RNA - Inside a cell, they are mobile, constantly changing shape and position - They contain an outer membrane, an inner membrane, and two internal compartments - They are similar in size and shape to bacteria - They contain their own DNA and RNA
Q: The synthesis of ATP in glycolysis occurs by which process?
Answer:
substrate-level phosphorylation
Q: True or false, or impossible to determine?
Answer:
Because living cells generate order by surviving, growing, and forming complex communities, they defy
the second law of thermodynamics.
false
Q: Protons are pumped across the mitochondrial inner membrane as electrons are transferred
through the mitochondrial electron transport chain. Which of the following statements about proton
pumping are correct?
Answer:
A. Protons are pumped into the matrix of the mitochondria.
B. The pH inside the mitochondrial matrix is higher than in the intermembrane space.
C. The mitochondria use the proton gradient to synthesize ATP.
D. The NADH dehydrogenase, cytochrome b-c1, and cytochrome oxidase complexes all pump protons
across the membrane.
B, C, D
Q: Antimycin A is a piscicide (fish poison) used to manage fisheries and kill invasive species.
Antimycin A blocks the transfer of electrons through the cytochrome b-c1 complex. What components
of the electron transport chain are bound to high-energy electrons after treating a mitochondrion with
antimycin A?
Answer:
NADH and the NADH dehydrogenase complex are bound to high-energy electrons while O2 and the
cytochrome c oxidase complex are not.
Q: Different molecules diffuse through the cytosol at different speeds. Which series represents the
correct order in which molecules will diffuse from the fastest to the slowest?
Answer:
tyrosine, ribosome, CO2, succinate dehydrogenase
CO2, tyrosine, succinate dehydrogenase, ribosome
Q: Which of the following can not be synthesized from intermediates formed during glycolysis and
the citric acid cycle in human cells?
Answer:
amino acids, lipids, nucleotides, cholesterol, vitamin C
vitamin C
Q: The electron-transport chain in mitochondria accepts high-energy electrons directly from which
molecule?
Answer:
NADH
Q: Is the following statement true or false based on chemical and biological reactions?
Energetically favorable reactions are those that create disorder by decreasing the free energy of the
system to which they belong.
Answer:
true, for all reactions biological and chemical
Q: Which of the following statements regarding NADPH and NADH is true?
Answer:
NADPH and NADH are used in separate biochemical pathways in cells
Q: True or false: The mass of the living cell cannot be greater than the amount of matter that is
absorbed by the cell.
Answer:
true
Q: The NADH generated during glycolysis and the citric acid cycle feeds its high-energy electrons to
which of the following?
Answer:
ADP, electron transport chain, citric acid cycle, FAD, H2O
the electron transport chain
Q: Some types of bacteria can survive under both aerobic and anaerobic conditions. Regardless of
whether oxygen is present, these cells maintain a proton gradient across the plasma membrane to drive
ATP synthesis and the import of nutrients. Under aerobic conditions, an H+ gradient across the plasma
membrane is produced by the transfer of electrons along the respiratory chain. When oxygen is present,
what would be expected to occur in the plasma membrane of these bacteria?
Answer:
Protons flow into the bacterial cell through ATP synthase, generating ATP.
Q: In the first reaction of glycolysis (the pathway that begins the oxidative breakdown of sugars), the
enzyme hexokinase uses ATP to catalyze the phosphorylation of glucose to glucose 6-phosphate and
ADP. The ΔG° of this reaction is a favorable -16.7 kJ/mole.Another sometimes active enzyme, called
glucose 6-phosphatase, effectively "reverses" this reaction, hydrolyzing glucose 6-phosphate back to
glucose and releasing a phosphate. The ΔG° of this reaction is -13.8 kJ/mole.Based on these values,
what is the ΔG° for the hydrolysis of ATP: ATP + H2O → ADP + Pi?
Answer: -30.5 kJ/mole
Q: To explore how yeast cells metabolize glucose, investigators use a DNA microarray to examine
the effect the sugar has on the expression of a variety of genes. Cultured yeast cells are supplemented
with high concentrations of glucose. mRNAs are extracted from the cells, converted into cDNAs, and
labeled with a fluorescent marker. The samples are then hybridized to a DNA microarray that includes
probes representing yeast genes.Shown here is a data set representing genes involved in ribosome
biogenesis and electron transport. Red indicates that supplementing the growth medium with glucose
has increased the expression of the genes, whereas green indicates that the added glucose has decreased
gene expression. Based on this data, what can be concluded about how yeast cells behave when grown
in the presence of high concentrations of glucose?
Answer:
Yeast cells exposed to high concentrations of glucose grow by fermentation.
Q: In the absence of oxygen, in cells that cannot carry out fermentation, glycolysis would halt at
which step?
Answer:
The oxidation of glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate
Q: Most of the energy released by oxidizing glucose is saved in the high-energy bonds of what
molecules?
Answer:
ATP and other activated carriers
Q: Consider two molecules that associate with each other through hydrogen bonds. How tightly will
the two molecules bind as the equilibrium constant, K, becomes larger for this association?
Answer:
They will bind more tightly.
Q: True or false: The free-energy change (ΔG) and the standard free-energy change (ΔG°) of a
reaction differ in that ΔG depends on the concentrations of the molecules in the reaction, whereas for
Answer:
ΔG°, these concentrations are set to fixed values.
True
Q: For many anaerobic microorganisms, which metabolic pathway is the principal source of ATP?
Answer:
glycolysis
Q: In what ways can mitochondria adapt to the changing needs of a cell?
Answer:
They can change their location.
They can change their number.
They can change their shape.
Q: Which of these glycolytic reactions is catalyzed by a kinase?
Answer:
1,3-bisphosphoglycerate → 3-phosphoglycerate
glucose → glucose 6-phosphate
fructose 6-phosphate → fructose 1,6-bisphosphate
Q: Where does the oxidative (oxygen-dependent) stage of the breakdown of food molecules occur in
a eukaryotic cell?
Answer:
mitochondrion
Q: Which statement about polymers is true?
Answer:
Polymer synthesis requires an input of free energy and involves the release of water.
Q: Which statement about enzymes is not true?
A. An enzyme can force an energetically unfavorable reaction to take place inside the cell.
B. Enzymes can speed up energetically favorable reactions.
C. Enzymes can help build large polymers.
D. Enzymes reduce the activation energy required to initiate a spontaneous reaction.
Answer:
An enzyme can force an energetically unfavorable reaction to take place inside the cell.
Q: In mitochondria, what is the final electron acceptor in the electron-transport chain?
Answer:
oxygen (O2)
Q: Which energy conversion characterizes photosynthesis?
Answer:
electromagnetic (light) energy → chemical bond energy
Q: What is true of mobile electron carriers?
Answer:
They ferry electrons between one respiratory complex and the next
Q: The movement of electrons through the electron-transport chain in mitochondria does which of
the following?
Answer:
pumps protons out of the mitochondrial matrix
Q: True or false: Activated carriers that transfer methyl, carboxyl, and glucose groups for the
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