Chapter 7
1. If a red blood cell and a plant cell were placed in seawater, what would happen to the two types of cells?
Both cells would gain water by osmosis; the red blood cell would burst, and the plant cell would increase in turgor pressure.
The red blood cell would burst, and the plant cell would shrink.
The red blood cell would shrink, and the plant cell would gain water.
Both cells would lose water; the red blood cell would shrivel, and the plant plasma membrane would pull away from the cell
wall.
Seawater is isotonic to both cells, therefore, neither cell will change as there will be no movement of water into or out of the
cells.
2. Which of the following processes and organelle(s) accounts for the replacement of lipids and proteins lost from the
plasma membrane?
Endocytosis and Golgi
Receptor-mediated endocytosis and smooth ER and Golgi
Active transport and the rough endoplasmic reticulum
Flip-flop of phospholipids from one side of the plasma membrane to the other and the Golgi
Exocytosis and smooth and rough ER
3. Which of the following statements about the role of phospholipids in the structure and function of biological membranes
is correct?
Phospholipids form a structure in which the hydrophobic portion faces outward.
They are triacylglycerols, which are commonly available in foods.
Phospholipids form a selectively permeable structure.
Phospholipids are completely insoluble in water.
Phospholipids form a single sheet in water.
4. All cells have voltages across their membranes. This voltage is called a(n) __________ and is often maintained by
__________.
membrane potential; electrogenic pumps
None of the listed responses is correct.
iotonic solution; diffusion
concentration gradient; osmosis
electrochemical gradient; diffusion
5. Which of these statements describes some aspect of facilitated diffusion?
Facilitated diffusion of solutes occurs through phospholipid pores in the membrane.
There is only one kind of protein pore for facilitated diffusion.
Facilitated diffusion is another name for osmosis.
Facilitated diffusion of solutes may occur through channel or transport proteins in the membrane.
Facilitated diffusion requires energy to drive a concentration gradient.
6. Which of the following is correct regarding peripheral proteins?
They exhibit only hydrophobic properties.
These proteins exhibit both hydrophilic and hydrophobic properties.
These proteins are found only on the surface of the plasma membrane.
They have no specific function in the plasma membrane.
They span the entire phospholipid bilayer.
7. Why is energy required for active transport?
To allow the movement of water from a hypotonic solution to a hypertonic solution
To allow the movement of water from a hypotonic solution to a hypertonic solution
To allow the movement of solutes down their concentration gradient
Because it helps maintain water balance in cells without walls
Because it moves solutes against their concentration gradient
8. Which of the following statements concerning carbohydrates associated with the plasma membrane is correct?
Membrane carbohydrates function primarily in cell-cell recognition.
The carbohydrate composition of most eukaryotic plasma membranes is quite similar.
Carbohydrates associated with the plasma membrane are located on both surfaces of the membrane.
Carbohydrates on the plasma membrane are typically short chains of between two and five monosaccharides.
Carbohydrates are only found associated with the membranes of prokaryotic cells.
9. Which of the following is a correct difference between active transport and facilitated diffusion?
Active transport can move solutes in either direction across a membrane, but facilitated diffusion can only move in one
direction.
Active transport requires energy from ATP, and facilitated diffusion does not.
Facilitated diffusion can move solutes against a concentration gradient, and active transport cannot.
Active transport involves transport proteins, and facilitated diffusion does not.
Facilitated diffusion involves transport proteins, and active transport does not.
10. What function do carbohydrates fulfill in the plasma membrane?
They contribute to its selective permeability.
They contribute to its “fluid” characteristic.
They facilitate enzymatic processes.
Cell-to-cell recognition
Transport of molecules across the membrane
11. Which of the following cell structures exhibits selective permeability between a cell and its external environment?
Lysosomes
Endoplasmic
Plasma membrane
Chloroplasts
Mitochondria
12. Which of the following is correct regarding integral proteins?
These proteins exhibit both hydrophilic and hydrophobic properties.
They exhibit only hydrophobic properties.
These proteins are found only on the surface of the plasma membrane.
They have no specific function in the plasma membrane.
They exhibit only hydrophilic properties.
13. The sodium-potassium pump __________.
transports sodium ions out of the cell
transports potassium ions into the cell
transports glucose into the cell
does not require energy to function
transports sodium ions out of the cell and transports potassium ions into the cell
14. Which of the following plant cells would exhibit the most turgor pressure?
A cell placed in an isotonic solution
All of the listed responses are correct.
A cell placed in a hypotonic solution
A cell placed in a hypertonic solution
None of the listed responses is correct.
15. Which of the following substances would be most likely to pass through the plasma membrane without the help of a
transport protein?
A negatively charged ion
Glucose
Water
A nonpolar molecule, such as a hydrocarbon
A large polar molecule
16. The plasma membrane exhibits selective permeability. This means that __________.
the structure of the plasma membrane does not affect its permeability
the plasma membrane allows some substances to flow through it more easily than others
the plasma membrane allows any substance to flow through it easily
the plasma membrane does not allow any substance to flow through it
proteins in the membrane do not affect its permeability
17. Which of the following structural arrangements of the components in biological membranes facilitates the cell
membrane's property of selective permeability?
A phospholipid bilayer with proteins scattered on the surfaces of the membranes
Proteins embedded in two layers of phospholipids
A layer of protein coating a layer of phospholipid
Phospholipids sandwiched between two layers of protein
Proteins sandwiched between two layers of phospholipids
18. A cell is placed into a solution and the cell shrinks. Which of the following is true regarding the solution?
The solution is hypertonic.
The solution has the same solute concentration as the cell.
None of the listed responses is correct.
The solution is hypotonic.
The cell is hypertonic.
19. In facilitated diffusion, channel proteins provide openings in the plasma membrane for substances to flow through
without changing structure, and carrier proteins allow passage of substances through the plasma membrane after undergoing
a subtle change in shape.
20. A nursing infant is able to obtain disease-fighting antibodies, which are large protein molecules, from its mother's milk.
These molecules probably enter the cells lining the baby's digestive tract via which process?
Passive transport
Endocytosis
Exocytosis
Active transport
Osmosis
21. How does cholesterol affect membrane fluidity?
At lower temperatures, it makes the membrane more fluid.
It has no effect on membrane fluidity.
At body temperature, it makes the membrane more fluid.
It allows phospholipids to pack tightly together.
At body temperature, it makes the membrane less fluid.
22. Which of the following molecules is most likely to passively diffuse across the plasma membrane?
Hemoglobin
Glucose
Sodium ion
Carbon dioxide
DNA
23. Red blood cells contain approximately a 2% concentration of solutes. A red blood cell is placed into a solution that
contains a 4% concentration of solutes to which the cell is not permeable. What will happen to the red blood cell?
The cell will decrease in size as water flows out of it.
The solutes will diffuse out of the cell.
The solutes will diffuse into the cell.
Nothing will happen because the solution and the cell are isotonic to each other.
The cell will increase in size as water flows into it.
24. Which of the following statements about diffusion is true?
It always requires integral proteins of the cell membrane.
It is very rapid over long distances.
It is a passive process.
It requires expenditure of energy by the cell.
It occurs when molecules move from a region of lower concentration to a region of higher concentration.
25. Which of the following molecules are most abundant in the plasma membrane?
Proteins
Phospholipids
Water
Carbohydrates
Cholesterol
26. Cells A and B are the same size, shape, and temperature, but cell A is metabolically less active than cell B; cell B is
actively converting oxygen to water in cellular respiration. Oxygen will diffuse more rapidly into cell __________ because
__________.
B; the gradient of oxygen is oriented in the opposite direction compared to cell A
A; the diffusion gradient there is shallower
B; the diffusion gradient in cell B is steeper
B; the oxygen molecules inside cell B have a higher kinetic energy
A; its membrane transport proteins will not be saturated
27. Which of the following would be least likely to diffuse through a plasma membrane without the help of a transport
protein?
A small nonpolar molecule
A large polar molecule
Any of the above would easily diffuse through the membrane.
Dissolved gases such as oxygen or carbon dioxide
A large nonpolar molecule
28. The internal solute concentration of a plant cell is about 0.8M. To demonstrate plasmolysis, it would be necessary to
suspend the cell in what solution?
0.8M
0.4M
distilled water
1.0M
150m
29. Which of the following statements about passive transport is correct?
Passive transport permits the solute to move in either direction, but the net movement of the population of solute molecules
occurs down the concentration gradient of the molecule.
In passive transport, solute movement stops when the solute concentration is the same on both sides of the membrane.
Passive transport operates independently of the concentrations of the moving solute.
Passive transport operates independently of diffusion.
Passive transport does not occur in the human body.
30. How does the “fluid mosaic model” describe the structure of the plasma membrane?
The fluid characteristic is due to the presence of carbohydrates, and the mosaic characteristic is due to the presence of
phospholipids.
Only the proteins in the membrane contribute to its fluidity.
None of the listed responses is correct.
The plasma membrane is a rigid structure that exhibits little flexibility.
Proteins in the membrane contribute to the mosaic quality of the membrane while the lateral and rotational movements of
phospholipids contribute to its fluidity.
Chapter 8
1. At low temperatures, a particular enzyme catalyzes a reaction, but at a slow rate. At high temperatures, the enzyme is
completely inactive. What statement best explains the difference in how temperature affects the function of this enzyme?
At low temperatures, there is not enough free energy for the enzyme to function at a high rate, and at high temperatures, the
enzyme is denatured, leaving it nonfunctional.
The enzyme functions best at both low and high temperatures.
Temperature has no effect on enzyme function.
High temperature provides the optimal environment in which this enzyme functions.
Low temperatures cause the enzyme to denature, and high temperatures cause the enzyme to move too fast to bind to its
substrate.
2. Cells use ATP constantly, but ATP is considered a renewable resource. What process makes this possible?
ATP can be regenerated by the addition of a phosphate group to ADP.
ADP and ATP are stored in large amounts in a cell.
ADP is generated by the addition of a phosphate group to ATP.
None of the listed responses is correct.
The hydrolysis of ATP is an irreversible reaction.
3. An exergonic (spontaneous) reaction is a chemical reaction that __________.
leads to a decrease in the entropy of the universe
releases energy when proceeding in the forward direction
is common in anabolic pathways
occurs only when an enzyme or other catalyst is present
cannot occur outside of a living cell
4. As ATP begins to build up in a cell, metabolism slows down. How does this happen?
Excess ATP causes many of the enzymes involved in metabolism to denature.
None of the listed responses is correct.
ATP acts as an allosteric inhibitor to many of the enzymes involved in metabolism, thus slowing their function.
ATP acts as an activator, increasing the rate of its production.
ATP binds to the active sites of many of the enzymes involved in metabolism, causing them to stop functioning.
5. At low pH, a particular enzyme catalyzes a reaction at a high rate. At neutral pH, the enzyme is completely inactive.
What statement best explains the difference in how pH affects the function of this enzyme?
The enzyme functions best at both low and neutral pH.
The enzyme is adapted for low pH but is denatured at neutral pH, leaving it nonfunctional.
Low pH causes the enzyme to denature, and neutral pH causes the enzyme to function normally.
pH has no effect on enzyme function.
Neutral pH provides the optimal environment in which this enzyme functions.
6. The process of stabilizing the structure of an enzyme in its active form by the binding of a molecule is an example of
allosteric regulation.
7. If the entropy of a living organism is decreasing, which of the following is most likely to be occurring simultaneously?
The first law of thermodynamics is being violated.
The entropy of the organism's environment must also be decreasing.
Heat is being used by the organism as a source of energy.
Energy input into the organism must be occurring to drive the decrease in entropy.
In this situation, the second law of thermodynamics must not apply.
8. Which of the following correctly states the relationship between anabolic and catabolic pathways?
Energy derived from catabolic pathways is used to drive the breakdown of organic molecules in anabolic pathways.
Anabolic pathways synthesize more complex organic molecules using the energy derived from catabolic pathways.
Catabolic pathways produce usable cellular energy by synthesizing more complex organic molecules.
Degradation of organic molecules by anabolic pathways provides the energy to drive catabolic pathways.
The flow of energy between catabolic and anabolic pathways is reversible.
9. What would the value of ΔS be for a chemical reaction in which a molecule is broken down into smaller components?
Positive
Neutral
Negative
Zero
10. Which of the following statements is correct regarding kinetic and potential energy?
Potential energy cannot be converted to kinetic energy.
Kinetic energy is associated with the relative motion of objects, and potential energy is the energy that matter possesses
because of its location or structure.
Chemical energy is a type of kinetic energy, and thermal energy is a type of potential energy.
None of the listed responses is correct.
Potential energy is related to the relative motion of objects, and kinetic energy is the energy that matter possesses because of
its location or structure.
11. In general, the hydrolysis of ATP drives cellular work by releasing free energy that can be coupled to other reactions
12. Which of the following statements is correct regarding ATP?
The energy in an ATP molecule is released through hydrolysis of one of the phosphate groups.
ATP molecules do not release free energy when hydrolyzed.
The energy in an ATP molecule is released from the ribose group.
The energy in an ATP molecule is released from the adenine group.
ATP cannot transfer energy to other molecules.
13. Which of these statements about enzyme inhibitors is true?
A competitive inhibitor binds to the enzyme at a place that is separate from the active site.
The action of inhibitors may be reversible or irreversible.
When the product of an enzyme or an enzyme sequence acts as its inhibitor, this is known as positive feedback.
A noncompetitive inhibitor does not change the shape of the active site.
Inhibition of enzyme function by compounds that are not substrates is something that only occurs under controlled
conditions in the laboratory.
14. Which of the following is changed by the presence of an enzyme in a reaction?
The G value for the products
The activation energy
The magnitude of ΔG
The sign of ΔG
The G value for the reactants
15. ATP allosterically inhibits enzymes in ATP-producing pathways. The result of this is called feedback inhibition.
16. Which of the following statements about enzymes is true?
Enzymes speed up the rate of the reaction without changing the ΔG for the reaction.
Enzymes increase the rate of a reaction by raising the activation energy for reactions.
The more heat that is added to a reaction, the faster the enzymes will function.
Enzymes react with their substrate (form chemical bonds), forming an enzyme-substrate complex, which irreversibly alters
the enzyme.
All of the listed responses are correct.
17. Which of the following statements about the active site of an enzyme is correct?
The active site has a fixed structure (shape).
The active site may resemble a groove or pocket in the surface of a protein into which the substrate fits.
The structure of the active site is not affected by changes in temperature.
Coenzymes are rarely found in the active site of an enzyme.
The active site allows the reaction to occur under the same environmental conditions as the reaction without the enzyme.
18. Which of the following reactions would be endergonic?
HCl → H+ + Cl
ATP → ADP + Pi
Glucose + fructose → sucrose
All of the listed responses are correct.
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O
19. If the entropy of a living organism is decreasing, which of the following is most likely to be occurring simultaneously?
The entropy of the organism's environment must also be decreasing.
The first law of thermodynamics is being violated.
In this situation, the second law of thermodynamics must not apply.
Heat is being used by the organism as a source of energy.
Energy input into the organism must be occurring to drive the decrease in entropy.
20. An exergonic reaction releases free energy, and an endergonic reaction absorbs free energy.
21. What best characterizes the role of ATP in cellular metabolism?
The free energy released by ATP hydrolysis that may be coupled to an endergonic process via the formation of a
phosphorylated intermediate.
The ΔG associated with its hydrolysis is positive.
The charge on the phosphate group of ATP tends to make the molecule very water-soluble.
The release of free energy during the hydrolysis of ATP heats the surrounding environment.
It is catabolized to carbon dioxide and water.
22. Enzyme activity is affected by pH because
the binding of hydrogen ions to the enzyme absorbs energy and thus there may not be enough energy to overcome the
activation energy barrier
low pH will denature all enzymes
most substrates don't function well at high or low pH
high or low pH may disrupt hydrogen bonding or ionic interactions and thus change the shape of the active site
changes in pH can cause loss of cofactors from the enzyme
23. ATP allosterically inhibits enzymes in ATP-producing pathways. The result of this is called feedback inhibition.
24. Which of the following is true regarding metabolic pathways?
Metabolic pathways are not important to a cell’s ability to function.
Metabolic pathways consist of a series of reactions, each catalyzed by a different enzyme.
Each reaction in the pathway is catalyzed by the same enzyme.
Metabolic pathways consist of only anabolic pathways.
Metabolic pathways consist of a single chemical reaction.
25. Which of the following states the relevance of the first law of thermodynamics to biology?
Living organisms must increase the entropy of their surroundings.
Energy is destroyed as glucose is broken down during cellular respiration.
Photosynthetic organisms produce energy in sugars from sunlight.
The total energy taken in by an organism must be greater than the total energy stored or released by the organism.
Energy can be freely transformed among different forms as long as the total energy is conserved.
26. Which of the following statements about enzyme function is correct?
None of the listed responses is correct.
Enzymes can greatly speed up reactions, but they cannot change the net energy output because they cannot change the
activation energy.
Enzymes can lower the activation energy of reactions, but they cannot change the equilibrium point because they cannot
change the net energy output.
Enzymes can greatly speed up reactions, but they cannot change the activation energy because they cannot change the net
energy output.
Enzymes can change the equilibrium point of reactions, but they cannot speed up reactions because they cannot change the
net energy output.
27. Which of the following is an example of the second law of thermodynamics as it applies to biological reactions?
The aerobic respiration of one molecule of glucose produces six molecules each of carbon dioxide and water.
All of the listed responses are correct.
Cellular respiration releases some energy as heat.
None of the listed responses is correct.
All types of cellular respiration produce ATP.
28. How does ATP drive mechanical work inside a cell?
By binding to motor proteins
By phosphorylating a transport protein
By providing free energy to facilitate the formation of polymers from monomers
By removing a phosphate from a transport protein
By removing free energy from a chemical reaction
29. Which of the following statements correctly describes cofactors and coenzymes?
Neither cofactors nor coenzymes assist enzyme function.
Both are nonprotein enzyme helpers; but most coenzymes are metal ions, and most cofactors are organic molecules.
Cofactors that are metal ions activate enzymes, but coenzymes deactivate them.
Both cofactors and coenzymes act as allosteric inhibitors to various enzymes.
Both are nonprotein enzyme helpers; but most cofactors are metal ions, and coenzymes are organic molecules that are a
specific type of cofactor.
30. The primary manner in which cells manage their energy resources in order to do work is called energy coupling. Which
of the following statements accurately defines energy coupling?
Endergonic reactions drive exergonic reactions.
Exergonic reactions drive endergonic reactions.
Anabolic reactions drive catabolic reactions.
Chemical reactions in cells are always at equilibrium.
Endergonic and exergonic reactions occur independently of each other.
31. How does ATP drive transport work inside a cell?
By removing a phosphate from a transport protein
By providing free energy to facilitate the formation of polymers from monomers
By binding to motor proteins
By removing free energy from a chemical reaction
By phosphorylating a transport protein
32. Which of the following statements is correct regarding competitive and noncompetitive enzyme inhibitors?
Only competitive inhibitors affect enzyme function.
Competitive inhibitors bind to the active site of an enzyme while noncompetitive inhibitors bind to an enzyme away from
the active site.
Neither type of inhibitor affects enzyme function.
Inhibitors always bind irreversibly to an enzyme.
Competitive inhibitors do not bind directly to the active site of an enzyme while noncompetitive inhibitors do.