Exam 1

Question 1

(Q015) Table 2-14 indicates the number and arrangement of electrons in the first four atomic electron shells for selected elements. On the basis of the information in the chart and what you know about atomic structure, which elements will form ions with a net charge of +1 in solution?
A. Helium; neon
B. Magnesium; calcium
C. sodium; potassium
D. carbon; sulfur

Answer 1

C. sodium; potassium

Question 2

(Q046) Macromolecules in the cell can often interact transiently as a result of noncovalent interactions. These weak interactions also produce stable, highly specific interactions between molecules. Which of the factors below is the most significant in determining whether the interaction will be transient or stable?
A. surface complementarity between molecules
B. the concentration of each molecule
C. the rate of synthesis
D. the size of each molecule

Answer 2

A. surface complementarity between molecules

Question 3

(Q014) Table 2-14 indicates the number and arrangement of electrons in the first four atomic electron shells for selected elements. On the basis of the information in the chart and what you know about atomic structure, which elements are chemically inert?
A. helium; neon
B. magnesium; calcium
C. sodium; potassium
D. carbon; sulfur

Answer 3

A. helium; neon

Question 4

(Q012) A covalent bond between two atoms is formed as a result of the
A. loss of a proton from one atom.
B. loss of electrons from both atoms.
C. transfer of electrons from one atom to the other.
D. sharing of electrons.

Answer 4

D. sharing of electrons.

Question 5

(Q016) Table 2-14 indicates the number and arrangement of electrons in the first four atomic electron shells for selected elements. On the basis of the information in the chart and what you know about atomic structure, which elements will form ions with a net charge of +2 in solution?
A. helium; neon
B. carbon; sulfur
C. magnesium; calcium
D. sodium; potassium

Answer 5

C. magnesium; calcium

Question 6

(Q020) Polar covalent bonds are formed when the electrons in the bond are not shared equally between the two nuclei. Which one of these molecules contains polar bonds?
A. molecular oxygen
B. water
C. propane
D. methane

Answer 6

B. water

Question 7

(Q003) Which subatomic particles contribute to the atomic mass for any given element?
A. neutrons
B. protons
C. protons and neutrons
D. protons and electrons

Answer 7

C. protons and neutrons

Question 8

(Q013) An ionic bond between two atoms is formed as a result of the
A. sharing of electrons.
B. loss of a proton from one atom.
C. loss of electrons from both atoms.
D. transfer of electrons from one atom to the other.

Answer 8

D. transfer of electrons from one atom to the other.

Question 9

(Q042) Energy cannot be created or destroyed, but it can be converted into other types of energy. Cells harvest some of the potential energy in the chemical bonds of foodstuffs to generate stored chemical energy in the form of activated carrier molecules, which are often employed to join two molecules together in __________ reactions.
A. oxidation
B. dehydrogenation
C. hydrolysis
D. condensation

Answer 9

D. condensation

Question 10

(Q013) The best way to know if an organic molecule has been reduced is to see if there was an increase in the number of __________ bonds.
A. H–H
B. C–H
C. C–N
D. C–O

Answer 10

B. C–H

Question 11

(Q002) When there is an excess of nutrients available in the human body, insulin is released to stimulate the synthesis of glycogen from glucose. This is a specific example of a/an __________ process, a general process in which larger molecules are made from smaller molecules.
A. catabolic
B. biosynthetic
C. anabolic
D. metabolic

Answer 11

C. anabolic

Question 12

(Q017) ΔG° indicates the change in the standard free energy as a reactant is converted to product. Given what you know about these values, which reaction below is the most favorable?
A. glucose + fructose → sucrose ΔG° = +5.5 kcal/mole
B. ADP + P → ATP ΔG° = +7.3 kcal/mole
C. glucose → CO + H O ΔG° = -686 kcal/mole
D. glucose 1-phosphate → glucose 6-phosphate ΔG° = -1.7 kcal/mole

Answer 12

C. glucose → CO + H O ΔG° = -686 kcal/mole

Question 13

(Q015) Chemical reactions that lead to a release of free energy are referred to as “energetically favorable.” Another way to describe these reactions is
A. uncatalyzed.
B. activated.
C. spontaneous.
D. uphill.

Answer 13

C. spontaneous.

Question 14

(Q018) Catalysts are molecules that lower the activation energy for a given reaction. Cells produce their own catalysts, called
A. proteins.
B. cofactors.
C. complexes.
D. enzymes.

Answer 14

D. enzymes.

Question 15

(Q001) Chemical reactions carried out by living systems depend on the ability of some organisms to capture and use atoms from nonliving sources in the environment. The specific subset of these reactions that break down nutrients in food can be described as
A. anabolic.
B. metabolic.
C. catabolic.
D. biosynthetic.

Answer 15

C. catabolic.

Question 16

(Q004) The energy used by the cell to generate specific biological molecules and highly ordered structures is stored in the form of
A. light waves.
B. heat.
C. chemical bonds.
D. Brownian motion.

Answer 16

C. chemical bonds.

Question 17

Coiled coils are defined by all of the following EXCEPT:
A. Coiled coils are the hallmark of Alzheimer’s disease, forming the amyloid fibrils found in diseased brains.
B. they coil together due to their amphipathic nature
C. Two or even sometimes three heptad repeat coils wind together to form a superhelical bundle
D. they are comprised of “heptad repeats” where the 1st and 4th amino acids are hydrophobic

Answer 17

A. Coiled coils are the hallmark of Alzheimer’s disease, forming the amyloid fibrils found in diseased brains.

Question 18

(Q023) Which of the following statements is TRUE?
A. Disulfide bonds are more common for intracellular proteins, compared to extracellular proteins.
B. Disulfide bonds are formed mainly in proteins that are retained within the cytosol.
C. Disulfide bonds are formed by the cross-linking of methionine residues.
D. Disulfide bonds stabilize but do not change a protein’s final conformation.

Answer 18

D. Disulfide bonds stabilize but do not change a protein’s final conformation.

Question 19

Types of secondary structures found in proteins include all of the following EXCEPT:
A. alpha helix
B. beta sheet
C. phosphoryl group
D. coiled coil

Answer 19

C. phosphoryl group

Question 20

(Q001) Polypeptides are synthesized from amino acid building blocks. The condensation reaction between the growing polypeptide chain and the next amino acid to be added involves the loss of
A. a carboxylic acid group.
B. an amino group.
C. a carbon atom.
D. a water molecule.

Answer 20

D. a water molecule.

Question 21

(Q003) Complete the sentence with the best option provided below. The primary structure of a protein is the
A. lowest energy conformation.
B. amino acid composition.
C. average size of amino acid side chains.
D. amino acid sequence.

Answer 21

D. amino acid sequence.

Question 22

(Q017) Two or three α helices can sometimes wrap around each other to form coiled-coils. The stable wrapping of one helix around another is typically driven by __________ interactions.
A. hydrophilic
B. ionic
C. van der Waals
D. hydrophobic

Answer 22

D. hydrophobic

Question 23

Advantages of protein phosphorylation as a regulatory mechanism include all of the following EXCEPT:
A. It changes the chemical nature of S,T,Y, and H R-group sidechains from polar to basic in
nature.
B. it can trigger allosteric changes to alter activity
C. several different amino acids can be phosphorylated, meaning that a protein could be
regulated by different kinases and at different sites, increasing the potential complexity of
signaling
D. depending on the context, phosphorylation can be used to positively regulate or
negatively regulate a protein

Answer 23

A. It changes the chemical nature of S,T,Y, and H R-group sidechains from polar to basic in
nature.

Question 24

Regulation of a protein’s activity by the binding of a small nucleotide such as ATP or GTP has all of the advantages below EXCEPT:
A. its small size allows it to diffuse rapidly to the protein, a key advantage to speed up “multi-step” processes
B. its binding can cause allosteric changes in the protein that regulate its activity
C. it modifies a single amino acid on the protein it regulates, increasing the number of different options for regulatory complexity if it can bind more than one site
D. it can positively or negatively regulate the protein’s interaction with other proteins, depending on the context

Answer 24

C. it modifies a single amino acid on the protein it regulates, increasing the number of different options for regulatory complexity if it can bind more than one site

Question 25

Fluorescence recovery after photobleaching (FRAP) is a way to measure:
A. Mobility of a protein within the cell
B. The free energy of a protein.
C. The equilibrium constant for a given reaction
D. Change in the membrane potential.

Answer 25

A. Mobility of a protein within the cell

Question 26

(Q019) Membrane synthesis in the cell requires the regulation of growth for both halves of the bilayer and the selective retention of certain types of lipids on one side or the other. Which group of enzymes accomplishes both of these tasks?
A. phospholipases
B. flippases
C. convertases
D. glycosylases

Answer 26

B. flippases

Question 27

(Q033) Which mechanism best describes the process by which nutrients are taken up selectively at the apical surface of the epithelial cells that line the gut and released from their basal and lateral surfaces?
A. Proteins are tethered to the cell cortex.
B. Protein movement is limited by the presence of a diffusion barrier.
C. Proteins are tethered to the proteins on the surface of another cell.
D. Proteins are tethered to the extracellular matrix.

Answer 27

B. Protein movement is limited by the presence of a diffusion barrier.

Question 28

(Q001) Which of the following is most likely to occur after the lipid bilayer is pierced?
A. The membrane expands.
B. The membrane reseals.
C. The membrane collapses.
D. A tear is formed.

Answer 28

B. The membrane reseals.

Question 29

(Q017) Most animal fats form a solid at room temperature, while plant fats remain liquid at room temperature. Which of the following is a feature of lipids in plant membranes that best explains this difference?
A. higher levels of sterols
B. larger head groups
C. unsaturated hydrocarbons
D. longer hydrocarbon tails

Answer 29

C. unsaturated hydrocarbons

Question 30

(Q006) Which of the following statements is TRUE?
A. Membrane lipids diffuse within the plane of the membrane.
B. In eukaryotes, all membrane-enclosed organelles are surrounded by one lipid
bilayer.
C. In an aqueous environment, the formation of liposomes by phospholipids requires energy.
D. Membrane lipids frequently flip-flop between one monolayer and the other.

Answer 30

A. Membrane lipids diffuse within the plane of the membrane.

Question 31

(Q014) Membrane lipids are capable of many different types of movement. Which of these does not occur spontaneously in biological membranes?
A. rotation around the long axis of a fatty acid
B. moving between lipid layers
C. flexing of hydrocarbon chains
D. lateral movement

Answer 31

B. moving between lipid layers

Question 32

(Q041) We can estimate the relative mobility of a population of molecules along the surface of a living cell by fluorescently labeling the molecules of interest, bleaching the label in one small area, and then measuring the speed of signal recovery as molecules migrate back into the bleached area. What is this method called?
A. SDS
B. SPT
C. FRAP
D. GFP

Answer 32

C. FRAP

Question 33

Why does the part of the polypeptide chain that crosses the lipid bilayer of most transmembrane proteins usually exist as an alpha helix or beta barrel?
A. Because a rigid structure such as occurs with these conformations is needed to penetrate through a lipid bilayer.
B. Because in both an alpha helix or a beta barrel the polar peptide bonds of the polypeptide
backbone chain are H-bonded and completely shielded from the hydrophobic environment of the lipid bilayer by the hydrophobic amino acid side chains.
C. Because these secondary structures always form the correct length needed to traverse a lipid bilayer (20-24 amino acids)
D. Because both of these secondary structures are able to shield their polar groups away from the hydrophobic lipid bilayer due to the van der Waals forces.

Answer 33

B. Because in both an alpha helix or a beta barrel the polar peptide bonds of the polypeptide
backbone chain are H-bonded and completely shielded from the hydrophobic environment of the lipid bilayer by the hydrophobic amino acid side chains.

Question 34

A similarity between symporters and antiporters is:
A. Both transporters are responsive to the membrane potential, opening once threshold is reached.
B. Both transporters couple the movement of two different solutes across the cell membrane.
C. Both transporters operate using passive transport mechanisms.
D. Both transporters are coupled to ATP hydrolysis to drive solute transport across the membrane.

Answer 34

B. Both transporters couple the movement of two different solutes across the cell membrane.

Question 35

A transporter protein that is also described as a “pump”:
A. Always hydrolyzes ATP to function
B. Is specialized to allow ions to move through an open pore in response to a signal that triggers an allosteric change that opens the pore.
C. Operates via a passive transport mechanism to transport solutes from high concentration to low.
D. uses energy to transport a solute against its concentration or electrochemical gradient

Answer 35

D. uses energy to transport a solute against its concentration or electrochemical gradient.

Question 36

(Q013) Pumps are transporters that are able to harness energy provided by other components in the cells to drive the movement of solutes across membranes, against their concentration gradient. This type of transport is called
A. free diffusion.
B. passive transport.
C. active transport.
D. facilitated diffusion.

Answer 36

C. active transport.

Question 37

Q004) Cells use membranes to help maintain set ranges of ion concentrations inside and outside the cell. Which of the following ions is the most abundant inside a typical mammalian cell?
A. Cl-
B. K+
C. Ca 2+
D. Na+

Answer 37

B. K+

Question 38

(Q012) Transporters, in contrast to channels, work by
A. filtering solutes by size.
B. filtering solutes by charge.
C. a gating mechanism.
D. specific recognition of transport substrates.

Answer 38

D. specific recognition of transport substrates.

Question 39

The three ways that an ion channel can be gated include:
A. ligand-gated, voltage-gated, mechanically- (stress-) gated.
B. ligand-gated, ATP-gated, membrane-gated
C. temperature-gated, voltage-gated, NAD+ -gated
D. RNA-gated, diffusion-gated, osmotic pressure-gated

Answer 39

A. ligand-gated, voltage-gated, mechanically- (stress-) gated.

Question 40

(Q001) Which of the following channels would not be expected to generate a change in voltage by movement of its substrate across the membrane where it is found?
A. a sodium channel
B. a proton channel
C. a calcium channel
D. an aquaporin

Answer 40

D. an aquaporin

Question 41

Although covalent bonds are 10–100 times stronger than noncovalent interactions, many biological processes depend on the number and type of noncovalent interactions between molecules. Which of the noncovalent interactions below will contribute most to the strong and specific binding of two molecules, such as a pair of proteins?
A. van der Waals attractions
B. electrostatic attractions
C. hydrogen bonds
D. hydrophobic interactions

Answer 41

B. electrostatic attractions

Question 42

Figure 3-1 is an energy diagram for the reaction X → Y. Which equation below provides the correct calculation for the free-energy change when X is converted to Y?
Figure 3-1
A. a - c
B. a – b
C. c - a
D. a + b – c

Answer 42

C. c - a

Question 43

The potential energy stored in high-energy bonds is commonly harnessed when the bonds are split by the addition of __________ in a process called __________.
A. hydroxide; hydration
B. water; hydrolysis
C. acetate; acetylation
D. ATP; phosphorylation

Answer 43

B. water; hydrolysis

Question 44

What type of cellular energy does glucose contain?
A. biosynthetic
B. kinetic
C. heat
D. chemical

Answer 44

D. chemical

Question 45

Maintaining pH and salt concentrations is critical to keeping proteins functional. What is the molecular mechanism by which pH affects protein function?
A. The hydrogen bonds within the polypeptide backbone that form the secondary structures are completely disrupted.
B. A few of the polar R-groups can change charge, and the new attraction or repulsion can alter the shape of the protein.
C. The N- and C-terminus amino acids with their amino and carboxyl ends can change the shape of the entire protein.
D. Only the primary structure is altered, which changes the folding and function of the protein.

Answer 45

B. A few of the polar R-groups can change charge, and the new attraction or repulsion can alter the shape of the protein.

Question 46

In the polypeptide sequence shown below, which letter represents the peptide bond?
A
B
C
D

Answer 46

C

Question 47

Lysozyme is an enzyme that specifically recognizes bacterial polysaccharides, which render it an effective antibacterial agent. Into what classification of enzymes does lysozyme fall?
A. isomerase
B. hydrolase
C. nuclease
D. protease

Answer 47

B. hydrolase

Question 48

The correct folding of proteins is necessary to maintain healthy cells and tissues. The presence of unfolded proteins is associated with some neurodegenerative disorders such as Alzheimer’s disease, Huntington’s disease, and Creutzfeldt–Jakob disease (the specific faulty protein is different for each disease). What happens to these disease-causing, unfolded proteins?
A. They bind a different target protein.
B. They form structured filaments.
C. They are degraded.
D. They form protein aggregates.

Answer 48

D. They form protein aggregates.

Question 49

A lab has sequenced a novel cancer-causing gene in humans. What can we learn from the protein sequence by inputting the predicted protein sequence into a computer and conducting bioinformatic analysis?
A. the rate at which the protein will be degraded
B. the complete tertiary structure of this protein
C. how many protein-binding partners it will have, including its quaternary structure
D. how to predict the domains by matching the amino acids with another similar sequence

Answer 49

D. how to predict the domains by matching the amino acids with another similar sequence

Question 50

Proteins can assemble to form large complexes that work coordinately, like moving parts inside a single machine. Which of the following steps in modulating the activity of a complex protein machine is LEAST likely to be directly affected by ATP or GTP hydrolysis?
A. complex assembly
B. conformational change of protein components
C. translation of protein components
D. complex disassembly

Answer 50

C. translation of protein components

Question 51

The three-dimensional coordinates of atoms within a folded protein are determined experimentally. After researchers obtain a protein’s structural details, they can use different techniques to highlight particular aspects of the structure. What visual model best displays a protein’s secondary structures (α helices and β sheets)?
A. wire
B. backbone
C. space-filling
D. ribbon

Answer 51

D. ribbon

Question 52

Which of the following statements is true?
A. Nonpolar amino acids tend to be found in the interior of proteins.
B. There is free rotation around all covalent bonds in the polypeptide backbone.
C. The sequence of the atoms in the polypeptide backbone varies between different proteins.
D. Peptide bonds are the only covalent bonds that can link two amino acids in proteins.

Answer 52

A. Nonpolar amino acids tend to be found in the interior of proteins.

Question 53

Proteins bind selectively to small-molecule targets called ligands. The selection of one ligand out of a mixture of possible ligands depends on the number of weak, noncovalent interactions in the protein’s ligand-binding site. Where is the binding site typically located in the protein structure?
A. on the surface of the protein in the presence of ligand
B. on the surface of the protein
C. inside a cavity on the protein surface
D. buried in the interior of the protein

Answer 53

C. inside a cavity on the protein surface

Question 54

Cholesterol serves several essential functions in mammalian cells. Which of the following is NOT influenced by cholesterol?
A. membrane permeability
B. membrane thickness
C. membrane fluidity
D. membrane rigidity

Answer 54

B. membrane thickness

Question 55

Cells utilize several mechanisms for restricting the movement of membrane proteins within the plasma membrane. One of these mechanisms allows cells to form specialized attachment structures called focal adhesions to promote cell motility. Which of the following mechanisms describes how motile cells form focal adhesions on the plasma membrane?
A. Proteins are tethered to the proteins on the surface of another cell.
B. Proteins are tethered to the cell cortex.
C. Protein movement is limited by the presence of a diffusion barrier.
D. Proteins are tethered to the extracellular matrix.

Answer 55

D. Proteins are tethered to the extracellular matrix.

Question 56

With which of the following solvents would you expect phospholipids to be compatible?
A. hydrophobic solvents
B. hydrophilic solvents
C. both hydrophilic and hydrophobic solvents
D. neither hydrophilic nor hydrophobic solvents

Answer 56

C. both hydrophilic and hydrophobic solvents

Question 57

Which of the following membrane lipids does not contain a fatty acid tail?
A. cholesterol
B. a glycolipid
C. phosphatidylserine
D. phosphatidylcholine

Answer 57

A. cholesterol

Question 58

Which of the following statements is true regarding the behavior of lipids in cell membranes?
A. Individual lipids tumble end over end within a single monolayer.
B. The hydrocarbon tails of membrane lipids act like stiff rods.
C. Membrane lipids frequently flip-flop between one monolayer and the other.
D. Membrane lipids diffuse laterally within the plane of the membrane.

Answer 58

D. Membrane lipids diffuse laterally within the plane of the membrane.

Question 59

Which of the following was demonstrated by the cell fusion experiment depicted in the figure below?
A. redistribution of lipids via hydrocarbon tail flexion
B. lipid randomization via scramblase activity
C. lateral diffusion of membrane proteins
D. synthesis of fluorescently labeled membrane proteins

Answer 59

C. lateral diffusion of membrane proteins

Question 60

The following descriptions refer to the structures of various hydrophobic fatty acid tails in membrane phospholipids. Which one would yield the most highly mobile phospholipid?
A. 24 carbons with one double bond
B. 16 carbons with no double bonds
C. 15 carbons with two double bonds
D. 20 carbons with two double bonds

Answer 60

C. 15 carbons with two double bonds

Question 61

How does a bilayer arrangement of phospholipids result in higher entropy for the system and thus make membrane formation energetically favorable?
A. Fatty acid tails are highly saturated and flexible.
B. Hydrogen bonds form between neighboring polar head groups in the bilayer.
C. Water molecules form cagelike structures around hydrophobic molecules, thus encouraging the latter to cluster together and limit their contact with water.
D. Polar head groups form a hydrogen-bonding network at the interface with water.

Answer 61

C. Water molecules form cagelike structures around hydrophobic molecules, thus encouraging the latter to cluster together and limit their contact with water.

Question 62

Cells use membranes to help maintain set ranges of ion concentrations inside and outside the cell. Which of the negatively charged ions listed below is NOT primarily used to buffer positive charges inside the cell?
A. Cl-
B. HCO3-
C. OH-
D. PO43-

Answer 62

A. Cl-

Question 63

Voltage-gated channels contain charged protein domains, which are sensitive to changes in membrane potential. By responding to a threshold in the membrane potential, these voltage sensors trigger the opening of the channels. Which of the following best describes the behavior of a population of channels exposed to such a threshold?
A. A few channels remain closed and most open completely.
B. All channels open partly, to the same degree.
C. All channels open completely.
D. All channels open partly, each to a different degree.

Answer 63

A. A few channels remain closed and most open completely.

Question 64

Which of the following best describes the behavior of a gated channel?
A. It opens more frequently in response to a given stimulus.
B. It stays open continuously when stimulated.
C. It requires a stimulus to change from closed to open.
D. It opens more widely as the stimulus becomes stronger.

Answer 64

A. It opens more frequently in response to a given stimulus.

Question 65

Below is a list of molecules with different chemical characteristics. Knowing that all molecules will eventually diffuse across a phospholipid bilayer, select the option below that most accurately predicts the relative rates of diffusion of the following molecules (fastest to slowest):
alanine estrogen propanol sodium
A. estrogen > propanol > alanine > sodium
B. alanine > propanol > sodium > estrogen
C. sodium > propanol > alanine > estrogen
D. estrogen > propanol > sodium > alanine

Answer 65

A. estrogen > propanol > alanine > sodium

Question 66

What category of membrane transport are channels a part of?
A. diffusion
B. facilitated diffusion
C. active transport
D. secondary active transport

Answer 66

B. facilitated diffusion

Question 67

Although the extracellular environment has a high sodium ion concentration and the intracellular environment has a high potassium ion concentration, both must be neutralized by negatively charged molecules. In the extracellular case, what is the principal anion?
A. Cl-
B. PO43-
C. HCO3-
D. OH-

Answer 67

A. Cl-

Question 68

If Na+ channels are opened in a cell that was previously at rest, how will the resting membrane potential be affected?
A. Na+ does not affect the membrane potential.
B. It is permanently reset.
C. It becomes more negative.
D. It becomes more positive.

Answer 68

D. It becomes more positive.

Question 69

The amino acids glutamine and glutamic acid are shown in Figure 2-5. They differ only in the structure of part of their side chains (circled). At pH7, what type of interactions are possible for glutamic acid but not for glutamine?
A. ionic bonds
B. hydrogen bonds
C. covalent bonds
D. van der Waals interactions

Answer 69

A. ionic bonds

Question 70

To break a glycosidic bond, a(n) __________ reaction will be performed.
A. oxidation
B. isomerization
C. condensation
D. hydrolysis

Answer 70

D. hydrolysis

Question 71

Choose the combination of answers that best completes the following statement: When atoms are held together by __________, they are typically referred to as __________.
A. ionic interactions; molecules
B. double bonds; nonpolar
C. hydrogen bonds; molecules
D. ionic interactions; salts

Answer 71

D. ionic interactions; salts

Question 72

A chemical reaction is defined as spontaneous if there is a net loss of free energy during the reaction process. However, spontaneous reactions do not always occur rapidly. Favorable biological reactions require __________ to selectively speed up reactions and meet the demands of the cell.
A. ions
B. ATP
C. heat
D. enzymes

Answer 72

D. enzymes

Question 73

When elemental sodium is added to water, the sodium atoms ionize spontaneously. Uncharged Na becomes Na+. This means that the Na atoms have been
A. reduced.
B. oxidized.
C. hydrogenated.
D. protonated.

Answer 73

B. oxidized.

Question 74

The assembly of individual polypeptides into a complex tertiary structure like microtubules, intermediate filaments, or the viral capsid of the SV40 virus requires
A. a specific ATP-dependent chaperone protein used to bind other proteins of a similar size and shape.
B. disulfide bonds.
C. many noncovalent bonds between each subunit.
D. a few covalent bonds at strategic locations in the protein.

Answer 74

D. a few covalent bonds at strategic locations in the protein.

Question 75

Which of the following is NOT a feature commonly observed in β sheets?
A. antiparallel regions
B. parallel regions
C. coiled-coil patterns
D. extended polypeptide backbone

Answer 75

C. coiled-coil patterns

Question 76

Cyclic AMP (cAMP) is a small molecule that associates with its binding site with a high degree of specificity. Which types of noncovalent interactions are the most important for providing the “hand in a glove” binding of cAMP?
A. hydrophobic interactions
B. hydrogen bonds
C. van der Waals interactions
D. electrostatic interactions

Answer 76

B. hydrogen bonds

Question 77

The variations in the physical characteristics between different proteins are influenced by the overall amino acid compositions, but even more important is the unique amino acid
A. number.
B. orientation.
C. bond.
D. sequence.

Answer 77

D. sequence.

Question 78

Some proteins have α helices, some have β sheets, and still others have a combination of both. What makes it possible for proteins to have these common structural elements?
A. side-chain interactions
B. hydrogen bonds along or between strands of the protein backbone
C. specific amino acid sequences
D. the hydrophobic-core interactions

Answer 78

B. hydrogen bonds along or between strands of the protein backbone

Question 79

Consider the apical location of protein A expressed in epithelial cells, as illustrated in part A of Figure 11-3 below. When a molecule that chelates calcium is added to the cell culture medium, you observe a redistribution of protein A around the entire cell, as shown in part B. Which is most likely to be true about the role of calcium in maintaining an apical distribution of protein A?
A. Calcium is required to maintain the structural integrity of the junctional complex.
B. Calcium is a structural component of protein A.
C. Calcium is required for the binding of the junctional proteins to the cell cortex.
D. Calcium inhibits the intracellular transport of protein A.

Answer 79

A. Calcium is required to maintain the structural integrity of the junctional complex.

Question 80

Where does most new membrane synthesis take place in a eukaryotic cell?
A. on ribosomes
B. in the endoplasmic reticulum
C. in the plasma membrane
D. in the Golgi apparatus

Answer 80

B. in the endoplasmic reticulum

Question 81

Cells utilize several mechanisms for restricting the movement of membrane proteins within the plasma membrane. One of these mechanisms allows cells to present antigens to other cells to trigger the adaptive immune response. Which of the following mechanisms describes how antigen-presenting cells perform this function?
A. Proteins are tethered to the cell cortex.
B. Protein movement is limited by the presence of a diffusion barrier.
C. Proteins are tethered to the extracellular matrix.
D. Proteins interact with the proteins on the surface of another cell.

Answer 81

D. Proteins interact with the proteins on the surface of another cell.

Question 82

Three phospholipids, X, Y, and Z, are distributed in the plasma membrane as indicated in Figure 11-1. The composition of the extracellular (noncytosolic) layer is different from that of the cytosolic layer. Which of the following factors is responsible for establishing this compositional asymmetry?
A. lipase
B. hydrolase
C. flippase
D. lipoyl transferase

Answer 82

C. flippase

Question 83

Consider a transport vesicle containing a membrane glycoprotein. The glycoprotein and the vesicle’s phospholipids are delivered to the plasma membrane, as shown in the figure below. Which of the following is an accurate description of the outcome of this process?
A. The phospholipids that are delivered to the noncytosolic face of the plasma membrane used to be in the interior (luminal) face of the vesicle.
B. The portion of the glycoprotein that was inside of the vesicle ends up in the cytosol after it is delivered to the plasma membrane.
C. Some of the individual phospholipid molecules are released into the cytosol to prevent the plasma membrane, and thus the cell, from becoming too large.
D. The fusion event between the vesicle and the plasma membrane randomizes the phospholipids between the cytosolic and noncytosolic faces of the bilayer.

Answer 83

A. The phospholipids that are delivered to the noncytosolic face of the plasma membrane used to be in the interior (luminal) face of the vesicle.

Question 84

Some cells express aquaporin proteins—they are channel proteins that facilitate the flow of water molecules through the plasma membrane. What regulates the rate and direction of water diffusion across the membrane?
A. availability of ATP
B. aquaporin conformation
C. the concentration of water on either side of the membrane
D. resting membrane potential

Answer 84

C. the concentration of water on either side of the membrane

Question 85

Figure 12-1 illustrates changes in membrane potential during the formation of an action potential. What membrane characteristic or measurement used to study action potentials is indicated by the arrow?
A. effect of a depolarizing stimulus
B. threshold potential
C. action potential
D. resting membrane potential

Answer 85

B. threshold potential

Question 86

Active transport requires the input of energy into a system so as to move solutes against their electrochemical and concentration gradients. Which of the following is NOT one of the common ways to perform active transport?
A. Na+-coupled
B. K+-coupled
C. ATP-driven
D. light-driven

Answer 86

B. K+-coupled

Question 87

Which of the following occur without coupling transport of the solute to the movement of a second solute?
A. export of H+ from animal cells for pH regulation
B. export of Ca2+ from the cytosol
C. export of glucose out of gut epithelial cells
D. the export of Na+ from cells to maintain resting membrane potential

Answer 87

B. export of Ca2+ from the cytosol

Question 88

Which of the following statements about resting membrane potential is true?
A. The resting membrane potential for most animal cells is positive, because Na+ ions are so plentiful inside cells.
B. At the resting membrane potential, no ions enter or exit the cell.
C. The resting membrane potential for most animal cells is zero mV, because the positive and negative ions are in balance.
D. The resting membrane potential for most animal cells is negative, because the inside of the cell is more negatively charged than the outside of the cell.

Answer 88

A. The resting membrane potential for most animal cells is positive, because Na+ ions are so plentiful inside cells.

Question 89

Cells in the stem of a seedling that is grown in the dark orient their microtubules horizontally. How would you expect this to affect the growth of the plant?
A. The horizontal orientation of the microtubules will be associated with a horizontal orientation of cellulose microfibrils deposited in the cell walls. The growth of the cells will therefore be in a horizontal direction
B. The stem will develop a spiral growth pattern, optimizing resource utilization.
C. Horizontal microtubule orientation will promote efficient water absorption, leading to accelerated growth.
D. The horizontal orientation of the microtubules will be associated with a horizontal orientation of cellulose microfibrils deposited in the cell walls. The growth of the cells will therefore be in a vertical direction

Answer 89

D. The horizontal orientation of the microtubules will be associated with a horizontal orientation of cellulose microfibrils deposited in the cell walls. The growth of the cells will therefore be in a vertical direction

Question 90

Would you expect collagen mutations to be detrimental if only one of the two copies of a collagen gene is defective?
A. A single defective polypeptide chain will impair assembly, even if normal chains are present at the same time.
B. No, because the unaffected copy can compensate for the defective one, leading to improved collagen function.
C. Yes, but only if the defective copy is in a non-coding region of the collagen gene, making it inconsequential.
D. Yes, but only if the defective copy is inherited from both parents, as a single defective copy is harmless.

Answer 90

A. A single defective polypeptide chain will impair assembly, even if normal chains are present at the same time.

Question 91

Which of the following determines the direction in which cellulose microfibrils are laid down in the extracellular space of a plant cell?
A. amount of turgor pressure within a cell
B. availability of sugar monomers for cellulose microfibril elongation
C. orientation of microtubules in the cell wall
D. orientation of microtubules on the cytoplasmic side of the plasma membrane

Answer 91

D. orientation of microtubules on the cytoplasmic side of the plasma membrane

Question 92

Fibroblasts are the major cellular component in which tissues?
A. epithelial
B. nervous
C. muscle
D. connective

Answer 92

D. connective