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Multiple Choice Practice Questions
_____1. Trypsin and elastase are both enzymes that catalyze
hydrolysis of peptide bonds. But trypsin only cuts next to
lysine and elastase only cuts next to alanine. Why?
a. Trypsin is a protein, and elastase is not.
b. ΔG for the two reactions is different.
c. The shape of the active site for the two enzymes is different.
d. One of the reactions is endergonic, and the other is
exergonic.
_____2. How do competitive and noncompetitive enzyme
inhibitors differ?
a. Competitive inhibitors bind to the active site, whereas
noncompetitive inhibitors change the shape of the active site.
b. Competitive inhibitors have a higher energy of activation
than noncompetitive inhibitors have.
c. They function at different pH values.
d. Noncompetitive enzyme inhibitors are reversible, whereas
competitive inhibitors are irreversible.
_____3. This figure shows the effect of pH on the activity of
the enzymes pepsin, chymotrypsin, and arginase. Each
enzyme has a different substrate. Consider a solution (solution
1) with equal concentrations of all three substrates for the
three enzymes along with another solution (solution 2)
containing all three enzymes. The fastest way to obtain a
solution containing only pepsin substrate (removing the
substrates for chymotrypsin and arginase) from solution 1 is to
adjust the pH of solution 1 to _______ and add the enzyme
solution (solution 2).
A. 4
B. 6
C. 8
D. 10
_____4. Which of the following statements about metabolic
pathways is false?
a. They are a series of enzyme-catalyzed reactions.
b. Almost all are endergonic.
c. They are similar in all organisms.
d. Many are compartmentalized in eukaryotes.
_____5. Which statement about pyruvate is false?
a. It is the end product of glycolysis.
b. It becomes reduced during fermentation.
c. It is a precursor of acetyl CoA.
d. It is a protein.
_____6. More free energy is released during the citric acid
cycle than during glycolysis, but only 1 mole of ATP is
produced for each mole of acetyl CoA that enters the cycle.
Most of the remaining free energy produced during the citric
acid cycle is
a. used to reduce electron carriers NAD and FAD
b. lost as heat.
c. used to reduce pyruvate.
d. converted to kinetic energy.
_____7. The four large protein complexes in the electron
transport chain
a. transport electrons.
b. ensure the production of water and oxygen.
c. regulate the passage of water through the chain.
d. oxidize NADH.
_____8. According to the chemiosmotic theory, the energy for
the synthesis of ATP as electrons flow down the respiratory
chain is provided directly by the
a. reduction of NAD+.
b. diffusion of protons.
c. reduction of FAD.
d. hydrolysis of ATP.
_____9. During anaerobic respiration of one molecule of
glucose, the net production of ATP is _______ molecule(s).
a. one
b. two
c. three
d. six
_____10. Before starch can be used for respiratory ATP
production, it must be hydrolyzed to
a. fatty acids.
b. amino acids.
c. glucose.
d. oxaloacetate.
_____11. If a cell has an abundant supply of ATP, acetyl CoA
may be used
a. to enhance fermentation.
b. to enhance oxidative metabolism.
c. for fatty acid synthesis.
d. to convert glucose to glycogen.
_____12. When a suspension of algae is incubated in a flask in
the presence of light and CO2 and then transferred to the dark,
the reduction of 3-phosphoglycerate to glyceraldehyde 3phosphate is blocked. This reaction stops in the dark because
a. the reaction requires CO2.
b. the reaction is exergonic.
c. the reaction requires ATP and NADPH.
d. the reaction requires O2.
_____13. Plants are green because
a. chlorophylls reflect green light.
b. chloroplasts reflect blue light.
c. energized chlorophyll a emits green light.
d. chlorophylls absorb green light
_____14. Photosynthesis and respiration have which of the
following in common?
a. In eukaryotes, both processes reside in specialized
organelles.
b. ATP synthesis in both processes relies on the chemiosmotic
mechanism.
c. Both involve electron transport.
d. All of the above
_____15. The light reactions of photosynthesis provides the
Calvin cycle with
a. ATP and NADPH.
b. CO2 and glucose.
c. water and photons.
d. light and chlorophyll.
_____16. Refer to the diagram below. Which of the following
was proved by experiments tracing isotopes of oxygen through
the process of photosynthesis?
c. The citric acid cycle would be inhibited, but glycolysis
would not. Lactic acid accumulates.
d. The citric acid cycle and glycolysis would be stimulated.
_____20. Which statement given below best characterizes the
properties of a photosystem?
a. Photosystems do not contain proteins.
b. A photosystem consists of just reaction center chlorophylls.
c. There is only one photosystem in green plants.
d. A photosystem is a complex of pigments, proteins, and a
reaction center chlorophyll.
_____21. The main function of cellular respiration is the
a. conversion of energy stored in the chemical bonds of
glucose to an energy form that the cell can use.
b. recovery of NAD+ from NADPH.
c. conversion of kinetic to potential energy.
d. creation of energy in the cell.
_____22. The main function of photosynthesis is the
a. consumption of CO2.
b. production of ATP.
c. conversion of light energy to chemical energy.
d. production of O2.
_____23. The Calvin cycle results in the production of
a. glucose.
b. starch.
c. rubisco.
d. G3P.
a. CO2 is the source of the oxygen released during
photosynthesis.
b. All the oxygen gas produced during photosynthesis comes
from water.
c. The oxygen released by water is incorporated into glucose.
d. Oxygen is needed to made rubisco.
_____17. Activities such as amino acid synthesis and active
transport in plant cells are powered by
a. the light-dependent and light-independent reactions of
photosynthesis.
b. ATP from the light reactions of photosynthesis.
c. ATP from fermentation.
d. ATP from glycolysis and cellular respiration.
_____18. Which of the statements below about the citric acid
cycle is false?
a. The cycle releases less energy than glycolysis.
b. CO2 is released during operation of the cycle.
c. The cycle takes place in the mitochondrial matrix.
d. The cycle requires NAD+ and FAD.
_____19. Cyanide inhibits the enzyme in the mitochondrial
electron transport chain that reduces O2 to water. Suppose that
you add cyanide to a suspension of muscle cells from a rat.
Which statement given below is the most accurate with respect
to the effects of cyanide on glucose catabolism?
a. The citric acid cycle and glycolysis would be inhibited.
b. The citric acid cycle would be inhibited, but glycolysis
would not. Ethanol accumulates.
_____24. Which statement about enzymes is false?
a. They usually consist of proteins.
b. They change the rate of the catalyzed reaction.
c. They change the ΔG of the reaction.
d. They are sensitive to pH.
_____25. With the addition of the enzyme alcohol
dehydrogenase, the rate of reduction of acetaldehyde to
ethanol increases as the concentration of acetaldehyde is
increased. Eventually, the rate of the reaction reaches a
maximum, at which point further increases in the
concentration of acetaldehyde have no effect. Why?
a. All the alcohol dehydrogenase molecules are bound to
acetaldehyde molecules.
b. At high concentrations of acetaldehyde, the activation
energy of the reaction increases.
c. At high concentrations of acetaldehyde, the activation
energy of the reaction decreases.
d. The enzyme is no longer specific for acetaldehyde.
_____26. How does the second law of thermodynamics apply
to organisms?
a. As energy transformations occur, free energy increases and
unusable energy decreases.
b. To maintain order, life requires a constant input of energy.
c. The potential energy of chemical bonds can be converted to
kinetic energy.
d. Reactions occur only with an input of energy.
_____27. Which statement about oxidative phosphorylation is
false?
a. It forms ATP by the respiratory chain/ATP synthesis.
b. It is brought about by chemiosmosis.
c. It takes place in mitochondria.
d. Its functions can be served equally well by fermentation.
Graphs I-IV depict the effect of pH on the activity of four
different hydrolytic enzymes.
_____28. How does the reduction of pyruvate to lactic acid
during fermentation allow glycolysis to continue in the
absence of oxygen?
a. Water is formed during this reaction.
b. This reaction is a endergonic reaction.
c. This reaction is coupled to the oxidation of NADH to
NAD+.
d. This reaction is coupled to the formation of ATP.
_____29. Compared with fermentation, the aerobic pathways
of glucose metabolism produce
a. more ATP.
b. pyruvate.
c. fewer protons for pumping in the mitochondria.
d. less CO2.
_____30. In the light dependent reactions of photosynthesis,
electrons from _______ replenish chlorophyll molecules that
have given up electrons in photosystem II.
a. CO2
b. water
c. NADPH + H+
d. O2 gas
_____31. Which of the following statements regarding the
relationship between photosynthesis and cellular respiration in
plants is true?
a. Photosynthesis and Cellular respiration require light.
b. Cellular respiration occurs in specialized respiratory cells.
c. Cellular respiration and photosynthesis can occur in the
same cell.
d. Photosynthesis is limited to specialized plant cells and
cellular respiration does not occur in plant cells.
_____32. The enzyme sucrase increases the rate at which
sucrose is broken down into glucose and fructose. Sucrase
works by
a. increasing the amount of free energy of the reaction.
b. lowering the activation energy of the reaction.
c. decreasing the equilibrium constant of the reaction.
d. supplying energy to speed up the reaction.
_____ 33. The most likely explanation for the results shown
in Graph I is that
(A) pH affects the shape of the active site of the enzyme
(B) pH affects the temperature of the reaction
(C) the enzyme has a quaternary structure
(D) the enzyme has disulfide bonds
(E) pH affects the primary structure of the enzyme
Unit 1 Review Questions
_____ 1. If ATP breakdown (hydrolysis) is inhibited, which
of the following types of movement across cell membranes is
also inhibited?
(A) Movement of oxygen into a cell
(B) Movement of water through aquaporins
(C) Passage of a solute against its concentration gradient
(D) Facilitated diffusion of a permeable substance
_____ 2. Which of the following depicts the most probable
pathway of processing and packaging a secretory protein
within a eukaryotic cell?
(A) Secretory vesicle  rough endoplasmic reticulum 
Golgi body  cell membrane
(B) Rough endoplasmic reticulum  Golgi body 
secretory vesicles  cell membrane
(C) Golgi body  secretory vesicles  rough
endoplasmic reticulum  cell membrane
(D) Secretory vesicles  Golgi body  rough
endoplasmic reticulum  cell membrane
(E) Golgi body  rough endoplasmic reticulum 
secretory vesicles  cell membrane
_______ 3. A biologist wants to use a radioactive isotope
of nitrogen to radiolabel certain molecules in a culture of
cells she is growing. If the biologist uses 15N, which of
the following groups of macromolecules will be labeled in
the culture of cells?
(A) Phospholipids
(B) Nucleic acids
(C) Proteins
(D) Nucleic acids and proteins
The solutions in the two arms of this U-tube are separated by a
membrane that is permeable to water and glucose but not to
sucrose. Side A is half filled with a solution of 2 M sucrose
and 1 M glucose. Side B is half filled with 1 M sucrose and 2
M glucose. Initially, the liquid levels on both sides are equal.
_______4. Which of the following statements describes
what will occur in the U-tube after the solutions have
been allowed to rest for 60 minutes?
(A) The system will reach equilibrium as the net
movement of water will equal zero.
(B) Sucrose will move from Side A to Side B.
(C) Glucose will move from Side B to Side A and
the liquid level will be higher on Side A.
(D) Glucose will move from Side B to Side A and
the liquid level will be higher on Side B.
_______ 5. Muscle cells are specialized cells that carry
out a multitude of tasks. One of these tasks includes
using ATP to drive myosin’s interaction with actin.
These cells would be expected to contain a large
proportion of which organelle relative to all others?
(A) nucleolus
(B) vacuoles
(C) mitochondria
(D) lysosomes
_______ 6. The functionality of a protein is determined
by its shape when it is in its native conformation. The
native conformation of a protein is determined by the set
of amino acids that compose the protein’s sequence. A
certain protein consists of 325 amino acids. What is the
most likely result if one of the amino acids in the protein
were changed?
(A) The primary structure of the protein would not
be altered but its tertiary structure and function
would be altered.
(B) The tertiary structure would be changed but the
proteins function would not be affected.
(C) The primary structure, tertiary structure and the
biological function would all be altered.
(D) There would be no change to the structure or the
function of the protein.
_______ 7. Mammalian blood contains the equivalent of
0.15 M NaCl. Seawater contains the equivalent of 0.45 M
NaCl. What will happen if red blood cells are transferred
to seawater?
(A) Water will leave the cells, causing them to
shrivel and collapse.
(B) NaCl will be exported from the red blood cells
by facilitated diffusion.
(C) The blood cells will take up water, swell, and
eventually burst.
(D) NaCl will passively diffuse into the red blood
cells.
_______ 8. Specialized cells in the adrenal gland produce
the hormone epinephrine, made of amino acids, and store
it in vesicles. To release epinephrine these vesicles are
carried to the plasma membrane and fuse with it. Which
mode of transport is used to release epinephrine?
(A) phagocytosis
(B) simple diffusion
(C) exocytosis
(D) protein pumps
_______ 9. Polysaccharides, triglycerides and proteins
are similar in that they
(A) Are synthesized from monomers by the process
of hydrolysis.
(B) Are synthesized from subunits by dehydration
synthesis.
(C) Are synthesized as a result of peptide bond
formation between monomers.
(D) Are decomposed into their subunits by
dehydration synthesis.
Beaker 1
Beaker 2
Beaker 3
Beaker 4
_______ 10. Which of the following conclusions can the
student reach upon collecting data for this investigation?
(A) The bag in Beaker 1 will gain the most
mass.
(B) The bag in Beaker 2 will lose the most mass.
(C) The bag in Beaker 4 has a lower solute
potential than its surrounding solution.
(D) All bags will lose water.