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Biochemistry > Exam 2 > Flashcards

Exam 2 Flashcards

1
Q

Which amino acid would most likely participate in general acid-base catalysis under basic conditions?

-Tyr
-Ala
-Gln
-Leu

A

Tyr

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2
Q

Which of the following mechanisms can affect enzymatic activity?

-substrate availability
-covalent modification
-cleavage of a zymogen
-all of the above

A

All of the above

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3
Q

Which of the following statements is FALSE about allosteric enzymes?

-They are most active in the relaxed (R) form
-They produce a sigmoidal curve
-The regulators associated with them bind only to the active site
-They work quickly and are direct

A

The regulators associated with them bind only to the active site

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4
Q

Which one of the following mechanisms is NOT known to play a role in the reversible alteration of enzyme activity?

-Alteration of the synthesis or degradation rate of an enzyme
-Allosteric response to a regulatory molecule
-Interactions between catalytic and regulatory subunits
-Activation by cleavage of an inactive zymogen
-Covalent modification of the enzyme

A

Activation by cleavage of an inactive zymogen.

(The activation of enzymes by proteolytic cleavage is irreversible.)

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5
Q

Which of the following statements regarding allosteric enzymes is true?

-They are always oligomeric
-They are generally found at regulatory sites in metabolic pathways
-They are subject to regulation by both positive and negative effectors.
-A plot of velocity vs. [substrate] often yields a sigmoidal curve
-All of the above

A

All of the above

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6
Q

Which form of protein regulation is irreversible?

A

Proteolytic cleavage

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7
Q

Which form of protein regulation occurs most quickly?

A

Allostery

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8
Q

Which form of protein regulation is most specific?

A

Allostery

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9
Q

Which form of protein regulation has broad specificity and is reversible?

A

Phosphorylation

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10
Q

The Lineweaver-Burk plot is also known as the double-_____ plot.

A

reciprocal

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11
Q

Allosterism…

-means “other shape”
-is induced by binding of another molecule to a protein
-is important to protein regulation
-leads to change in conformation and activity
-all of the above

A

All of the above

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12
Q

Proteins/enzymes that can be regulated allosterically…

i. show a hyperbolic Michaelis-Menten curve
ii. can be regulated by molecules that differ structurally from a substrate
iii. can be both activated and inhibited
iv. undergo only competitive inhibition

-i, ii, and iii
-i, iii, iv
-i and ii
-i, ii, iii, iv
-ii and iii

A

ii and iii

-Can be regulated by molecules that differ structurally from a substrate
-Can be both activated and inhibited

(Shows a sigmoidal Michaelis-Menten curve and competitive inhibition is associated with orthosteric regulation)

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13
Q

Enzymes that are allosterically regulated…

-show an activity vs. substrate concentration curve that is sigmoidal
-may be stimulated by allosteric activators
-when inhibited show an activity curve shifted to the right
-both A and B
-all of the above

A

All of the above

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14
Q

Which of the following statements about phosphorylation of enzymes is FALSE?

-The phosphorylation of an enzyme results in a change in its conformation, thereby increasing its activity.
-Phosphorylation is a reversible covalent modification
-The phosphorylation of enzymes is catalyzed by other enzymes called kinases
-The phosphorylation of enzymes is one mechanism via which hormones elicit an intracellular response.

A

The phosphorylation of an enzyme results in a change in its conformation, thereby increasing its activity.

(The phosphorylation of an enzyme does alter its conformation, but this may cause either an increase OR a decrease in activity.)

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15
Q

Zymogens are not enzymatically active because _____.

-they do not contain the cofactors required for catalysis
-they are the product of mutated genes
-their active sites are distorted and incapable of enzymatic activity
-the pH of their environment is not optimal for activity
-none of the above

A

their active sites are distorted and incapable of enzymatic activity

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16
Q

Protein kinases are involved in ______.

-the digestion of drugs to potentially toxic by-products
-the degradation of enzymes to the component amino acids
-the phosphorylation of a wide variety of proteins
-the metabolism of drugs to water soluble, excretable compounds
-all of the above

A

the phosphorylation of a wide variety of proteins

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17
Q

What is the difference between allosteric and orthosteric regulation?

-All enzymes are regulated orthosterically only.
-All enzymes are regulated allosterically only.
-Only in allosteric regulation of an enzyme does the substrate bind to the active site
-In allosteric regulation of an enzyme, the substrate binds to the allosteric site
-In allosteric regulation of an enzyme, a molecule other than the substrate binds a site other than the active site.

A

In allosteric regulation of an enzyme, a molecule other than the substrate binds a site other than the active site.

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18
Q

In the sequential model of allosterism, as regulatory molecules bind to allosteric sites,

-the active site-containing subunit shifts from T to R state
-the active site-containing subunit is activated
-the entire complex exists in the T or R state
-subunits in the T state have high affinity
-both A and B

A

Both A and B

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19
Q

Heterotropic regulation

i. occurs with a molecule other than the protein’s substrate
ii. occurs with regulator binding at a site other than the active site
iii. influences substrate binding
iv. is a type of competitive inhibition

-i and ii
-ii and iii
-ii, iii, and iv
-i, iii, and iv
-i, ii, and iii

A

i, ii, and iii

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20
Q

As associated with hemoglobin, heme is considered a ____.

-catalyst
-subunit
-coenzyme
-cofactor
-none of the above

A

cofactor

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21
Q

In its reduced form, the central ion of the heme group of hemoglobin is _____.

-Cu+
-Cu2+
-Fe2+
-Fe3+
-none of the above

A

Fe2+

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22
Q

Myoglobin is _____; hemoglobin is _____.

-monomeric; dimeric
-monomeric; trimeric
-monomeric; tetrameric
-dimeric; trimeric
-dimeric; tetrameric

A

Monomeric; tetrameric

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23
Q

The individual hemoglobin subunits and myoglobin share similar _____ structure but have rather different _____ structure.

-primary; secondary
-secondary; tertiary
-primary; tertiary
-secondary and tertiary; primary
-primary and secondary; tertiary

A

secondary and tertiary; primary

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24
Q

A plot of the binding of oxygen to myoglobin as a function of pO2 gives a ____ shape; a similar plot for hemoglobin gives a _____ shape.

-sigmoidal; sigmoidal
-sigmoidal; hyberbolic
-hyberbolic; sigmoidal
-hyperbolic; hyperbolic
-hyperbolic; exponential

A

hyperbolic; sigmoidal

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25
Q

The idea that binding of one molecule of oxygen to hemoglobin enhances further binding of oxygen to hemoglobin is called _____.

-homologous binding
-cooperativity
-fractional saturation
-allosterism
-none of the above

A

Cooperativity

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26
Q

With respect to oxygen saturation, hemoglobin is _____ saturated at the pO2 of the lungs and _____ saturated at the pO2 of the tissue.

-20%; 20%
-25%; 20%
-50%; 20%
-50%; between 30 and 70%
->90%; 10-30%

A

> 90%; 10-30%

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27
Q

The Bohr effect refers to…

-the decrease in affinity of Hb (hemoglobin) for O2 when the pH goes down
-the decrease in affinity of Hb for O2 when the pH goes up
-the increase in the affinity of Hb for O2 when the O2 concentration goes up
-the decrease in the affinity of Hb for O2 when the BPG concentration goes up
-the decrease in the affinity of Hb for O2 when the BPG concentration goes down

A

The decrease in affinity of Hb (hemoglobin) for O2 when the pH goes down

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28
Q

The sequential model of allosterism states that ligand binding induces a conformational change in the subunit to which it binds.

-True
-False

A

True

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29
Q

What are the two conformations of hemoglobin?

-The T state (the conformation of deoxyhemoglobin) and the R state (the conformation of oxyhemglobin)
-The R state (the conformation of deoxyhemoglobin) and the T state (the conformation of oxyhemglobin)
-The T state (the conformation of deoxyhemoglobin) and the R state (the conformation of myoglobin)
-The T state (the conformation of myoglobin) and the R state (the conformation of deoxyhemglobin)

A

The T state (the conformation of deoxyhemoglobin) and the R state (the conformation of oxyhemglobin)

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30
Q

Glucose and galactose are ____ of each other.

-epimers
-enantiomers
-diastereomers
-anomers
-none of the above

A

epimers

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31
Q

Monosaccharides with the OH group on the left are considered ______.

A

L-sugars

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32
Q

What carbon determines L or D stereochemistry?

A

The penultimate carbon

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33
Q

A ____ carbon is a carbon that is bonded to the ring Oxygen and the hydroxyl group in the cyclic form.

A

anomeric

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34
Q

What are the names of the 2 monosaccharides that make up the disaccharide sucrose?

A

Glucose (glucopyranose) and fructose (fructofuranose)

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35
Q

The alpha configuration is a __-membered carbon ring.

A

6

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36
Q

The beta configuration is a ___-membered carbon ring.

A

5

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37
Q

Is sucrose a reducing sugar?

A

Sucrose is a nonreducing sugar because both anomeric carbons are involved in a glycosidic bond.

(The bond is unable to be “opened up” again. The structure is an acetal which is stable and unable to be oxidized.)

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38
Q

Cellulose _____.

-is a fructose polymer in which all residues are joined by an alpha-1,4 glycosidic linkage
-is a structural polysaccharide found in all organisms other than plants
-is a glucose polymer in which all residues are joined by a beta-1,4 glycosidic linkage
-can be easily digested by humans

A

is a glucose polymer in which all residues are joined by a beta-1,4 glycosidic linkage

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39
Q

The ______ sugars are monosaccharides in which a hydroxyl group is replaced with a hydrogen atom.

A

deoxy

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40
Q

Any sugar that has a free aldehyde group is called a(n) ______.

-aldohexose
-reducing sugar
-nonreducing sugar
-alditol
-ketose

A

reducing sugar.

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41
Q

Amylopectin contains primarily ____ glycosidic bonds with ____ glycosidic bonds as branch points.

-alpha(1–> 4); beta)1 –> 6)
-beta(1–> 4); alpha)1 –> 6)
-alpha(1–> 4); alpha)1 –> 2)
-beta(1–> 4); alpha)1 –> 4)
-alpha(1–> 4); alpha)1 –> 6)

A

alpha(1–> 4); alpha)1 –> 6)

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42
Q

In glycolysis, ____ moles of ATP and ____ moles of NADH are produced per one mole of glucose consumption.

A

2, 2

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43
Q

Which of the following statements regarding gluconeogenesis is TRUE?

-Fructose-2,6-bisphosphate activates gluconeogenesis
-It occurs actively in skeletal muscle during periods of exercise
-Gluconeogenesis is reciprocally regulated with glycogen synthesis
-It is like to occur when cellular ATP levels are high
-The conversion of phosphoenolpyruvate to 2-phosphoglycerate occurs in 2 steps.

A

It is like to occur when cellular ATP levels are high

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44
Q

Match the following showing reaction products of pyruvate:

Decarboxylation by pyruvate decarboxylase

A

Acetaldehyde

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45
Q

Match the following showing reaction products of pyruvate:

Carboxylation

A

Oxaloacetate

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46
Q

Match the following showing reaction products of pyruvate:

Transamination

A

Alanine

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47
Q

Match the following showing reaction products of pyruvate:

Reduction

A

Lactate

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48
Q

Match the following showing reaction products of pyruvate:

Decarboxylation by pyruvate dehydrogenase

A

Acetyl-CoA

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49
Q

Which of the following is NOT a direct product of pyruvate metabolism?

-Acetyl-CoA
-Lactate
-Oxaloacetate
-Phosphoenolpyruvate
-Both C and D are correct

A

Phosphoenolpyruvate

(Pyruvate cannot be converted to phosphoenolpyruvate by reversal of the pyruvate kinase of glycolysis.)

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50
Q

The conversion of triacylglycerides into fatty acids for energy generation is an example of which of the following?

-catabolism
-heterotropism
-anabolism
-anaerobism
-glycolysis

A

Catabolism

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51
Q

How many enzymes of glycolysis are control points for the pathway?

A

3

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52
Q

Which of the following is FALSE for catabolic pathways?

-They generate ATP
-They generate oxidized enzyme cofactors
-They extract usable chemical energy from fuel molecules
-They are oxidative

A

They generate oxidized enzyme cofactors.

(This statement is FALSE. Catabolic pathways generate reduced enzyme cofactors such as NADH and FADH2.)

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53
Q

Which of the following statements concerning metabolic pathways is TRUE?

-All reactions in a metabolic pathway are tightly regulated.
-Opposing metabolic pathways do NOT occur
-Metabolic pathways may have either a net positive or net negative free energy
-Many of the reactions in a metabolic pathway are thermodynamically reversible.

A

Many of the reactions in a metabolic pathway are thermodynamically reversible.

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54
Q

Pyruvate kinase is activated by _____ and _____ and inhibited by ______ and ______.

A

Activated by fructose-1,6-bisphosphate and insulin.

Inhibited by ATP and acetyl-CoA

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55
Q

Pyruvate has several metabolic fates depending on the cell, under aerobic or anaerobic conditions. Which one of the following is a metabolic fate for pyruvate?

-Decarboxylation to oxaloacetate
-Reduction to lactate
-Oxidative carboxylation to acetyl-CoA
-Oxidation to ethanol

A

Reduction to lactate

(Under anaerobic conditions in muscle cells, the reduction of pyruvate to lactate regenerates NAD+, which is necessary for glycolysis to continue.)

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56
Q

The simplest of all carbohydrates has ___ carbon atoms.

A

3

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57
Q

Carbohydrates that differ at one stereocenter are called _____.

-anomers
-epimers
-enantiomers
-diasteroisomers

A

Epimers

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58
Q

Which type of bond links the monomers of a polysaccharide?

-peptide bond
-glycosidic bond
-glucosidic bond
-phosphate ester bond

A

Glycosidic bond

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59
Q

The disaccharide commonly found in dairy products is ______.

A

Lactose

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60
Q

_______ is a homopolymer composed of beta(1,4)-linked N-acetyl-D-glucosamine residues that is the principal structural component of the exoskeleton of various groups of invertebrates.

A

Chitin

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61
Q

The molecular formula for a monosaccharide is _____.

A

CnH2nOn where n is greater than or equal to 3

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62
Q

Glucose and galactose are _____ of each other.

A

epimers

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63
Q

The ______ sugars are monosaccharides in which a hydroxyl group is replaced with a hydrogen atom.

A

deoxy

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64
Q

The bonding of alcohols to the anomeric center of carbohydrates results in the formation of a(n) ______ bond.

-anomeric
-amide
-glycosidic
-ester
-hydrogen

A

glycosidic

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65
Q

Any sugar that has a free aldehyde group is called a(n) _____.

-reducing sugar
-nonreducing sugar
-ketose
-aldohexose
-alditol

A

Reducing sugar

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66
Q

Which of the following sugars is not a reducing sugar?

-glucose
-ribose
-sucrose
-starch
-galactose

A

Sucrose

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67
Q

Which of the following is the major difference between glycogen and amylopectin?

-Glycogen contains alpha-glycosidic bonds; amylopectin contains beta-glycosidic bonds
-Glycogen is branched; amylopectin is linear
-Glycogen contains a reducing end; amylopectin does not
-Glycogen contains about twice the number of branch points as amylopectin
-Glycogen is found in plants; amylopectin is found in animals

A

Glycogen contains about twice the number of branch points as amylopectin

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68
Q

Which of the following are characteristic of cellulose?

-highly extended chains
-beta (1–> 4) glycosidic bonds
-extensive hydrogen bonding between individual molecules
-unbranched polymer
-all of the above

A

All of the above

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69
Q

Unlike proteins and oligonucleotides, polysaccharides ____.

-are readily metabolized in the absence of specialized enzymes
-often have branched structures
-are achiral
-are always completely water soluble
-are components of every known living organism

A

often have branched structures

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70
Q

Cellulose is _____.

-a linear copolymer of glucose and galactose
-a branched polymer of glucose
-a linear polymer of glucose with beta(1–>4) linkages
-a linear polymer of glucose with alpha(1–>4) linkages
-sometimes called starch

A

A linear polymer of glucose with beta(1–>4) linkages

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71
Q

Which chair conformation is the most stable and why?

A

The conformation with all substituents in the equatorial position is the most stable, as this reduces steric repulsion amongst the subtituents.

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72
Q

Sucrose is a ______ comprised of a molecule of glucose joined to a molecule of fructose through an ______ glycosidic linkage.

A

disaccharide; alpha-1,2

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73
Q

Maltose is a ______ made of two molecules of glucose joined via an ______ glycosidic linkage.

A

disaccharide; alpha-1,4

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74
Q

Lactose is a disaccharide of a molecule of glucose joined to a molecule of ______ through an ______ glycosidic linkage.

A

galactose; beta-1,4

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75
Q

A saccharide that has a free aldehyde group is called a(n) _______.

-ketose
-nonreducing sugar
-reducing sugar
-aldohexose
-alditol

A

Reducing sugar

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76
Q

In terms of structure, what is the main difference between alpha-amylose and cellulose?

-Cellulose is linear, but alpha-amylose is branched.
-Cellulose is formed by beta(1–>4)glycosidic bonds, but alpha-amylose is formed by alpha(1–>4) glycosidic bonds.
-Cellulose is branched, but alpha-amylose is a linear polymer
-Cellulose is a linear polymer of D-glucose, but alpha-amylose is a linear polymer of D-allose

A

Cellulose is formed by beta(1–>4)glycosidic bonds, but alpha-amylose is formed by alpha(1–>4) glycosidic bonds.

(They are both polymers of D-glucose, and differ only in the anomeric form used.)

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77
Q

A furanose is a ________.

A

5-membered ring

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78
Q

The first committed step in glycolysis is mediated by _____.

-hexokinase
-phosphofructokinase
-triose phosphate isomerase
-pyruvate kinase

A

Phosphofructokinase

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79
Q

Which of the following features are common to all anabolic pathways?

-They are oxidative
-Their overall free energy change is positive
-They require energy
-They break down complex molecules

A

They require energy.

(Anabolic pathways require electrons to make chemical bonds)

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80
Q

Which of the following is a method of directly regulating PFK-1?

-Feedback inhibition by fructose-2,6-bisphosphate
-Feed forward activation by phophosenolpyruvate
-By its phosphorylation in response to glucagon signaling
-Allosteric activation by ADP

A

Allosteric activation by ADP

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81
Q

When the energetic level (glucose) of the cell is low glycolysis is _____ and when the plasma glucose level is low glucogenesis is _____.

A

activated; activated

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82
Q

The reactions of glycolysis that are bypassed in gluconeogenesis are catalyzed by the enzymes ______.

A

-Glucose-6-phosphatase
-Fructose-1,6-bisphosphatase
-Pyruvate carboxylase
-Phosphoenolpyruvate carboxylase

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83
Q

In humans, which one of the following statements about gluconeogenesis is TRUE?

-Can result in the conversion of protein into glucose
-Helps to reduce blood glucose after a carbohydrate-rich meal
-Is essential in the conversion of fatty acids to glucose
-Requires the enzyme hexokinase

A

Can result in the conversion of protein into glucose

(Hexokinase is the first enzyme of glycolysis, it catalyzes an irreversible reaction in the glycolytic pathway and therefore cannot be part of gluconeogenesis.)
(The carbon atoms of most fatty acids cannot be converted to glucose.)
(Gluconeogenesis helps increase blood sugar during starvation)

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84
Q

Which of the following statements regarding gluconeogenesis is TRUE?

-Fructose-2,6-bisphosphate activates gluconeogenesis
-It occurs actively in skeletal muscles during periods of exercise.
-It is likely to occur when cellular ATP levels are high
-Gluconeogenesis is reciprocally regulated with glycogen synthesis
-The conversion of phosphoenolpyruvate to 2-phosphoglycerate occurs in two steps.

A

It is likely to occur when cellular ATP levels are high

(Fructose-2,6-bisphosphate inactivates gluconeogenesis as it inhibits fructose-1,6-bisphosphatase)
(Gluconeogenesis does not occur in skeletal muscle since it is lacking glucose-6-phosphatase, the last enzyme of the gluconeogenic pathway)
(Gluconeogenesis is reciprocally regulated with glycosis, its opposing pathway)
(The conversion of phosphoenolpyruvate to 2-phosphoglycerate occurs in a single step catalyzed by enolase. The conversion of pyruvate to phosphoenolpyruvate occurs in 2 steps.

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85
Q

Pyruvate dehydrogenase, the enzyme that catalyzes the conversion of pyruvate to acetyl-CoA, is a multi-subunit enzyme that requires which of the following vitamins and cofactors?

-lipoic acid, thiamine, ferredoxin, vitamin D
-thiamine pyrophosphate, lipoamide, nicotine adenine dinucleotide
-thiamine, ascorbic acid, niacin, pantothenic acid
-ferredoxin, thiamine, niacin, FMN

A

Thiamine pyrophosphate, lipoamide, nicotine adenine dinucleotide

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86
Q

Which of the following is NOT a direct product of pyruvate metabolism?

-Acetyl-CoA
-Lactate
-Oxaloacetate
-Phosphoenolpyruvate
-Both C and D are correct

A

Phosphoenolpruvate

(Pyruvate cannot be converted to phophoenolpyruvate by reversal of the pyruvate kinase reaction of glycolysis)
(Pyruvate is converted to phosphoenolpyruvate indirectly via oxaloacetate; however oxaloacetate formed from the carboxylation of pyruvate via pyruvate carboxylase)
(Lactate is formed from the reduction of pyruvate via lactate dehydrogenase)
(Acetyl-CoA is formed by the oxidative decarboxylation of pyruvate in a reaction catalyzed by pyruvate dehydrogenase)

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87
Q

Cells control or regulate the flux through metabolic pathways by means of

-allosteric control of enzymes
-covalent modification of enzymes
-genetic control of the concentrations of enzymes
-altering the delta G value of reactions

A

-allosteric control of enzymes
-covalent modification of enzymes
-genetic control of the concentrations of enzymes

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88
Q

In the catabolic pathway, major nutrients are _____ broken down mainly resulting in more _____ metabolites.

A

exergonically; oxidized

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89
Q

The products of glycolysis include ATP, NADH, and _____.

A

Pyruvate

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90
Q

The enzyme _____ is the major control point for glycolysis.

A

Phosphofructokinase

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91
Q

Which of the following enzymes catalyzes the transfer of a phosphoryl group from ATP to glucose?

-hexokinase
-phophoglucose isomerase
-glucose-6-phosphatase
-phophoglucose mutase
-A transfer such as this does not occur in glycolysis.

A

Hexokinase

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92
Q

What is the net equation for aerobic glycolysis?

A

Glucose + 2 ADP + 2 Pi + 2 NAD+ –> 2 pyruvate + 2 ATP + 2 NADH+ + 2 H2O + 4H+

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93
Q

Of the reaction types listed below, which type of reaction is NOT used in glycolysis?

-oxidation
-phosphorylation
-dehydration
-isomerization
-All are used in glycolysis

A

All are used in glycolysis

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94
Q

During reactions using the enzymes shown below, in which case is ATP produced?

-Phosphofructokinase (PFK)
-Phosphoglycerate kinase (PGK)
-Pyruvate kinase (PK)

A

-Phosphoglycerate kinase (PGK)
-Pyruvate kinase (PK)

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95
Q

In which of the following metabolic conversions is ATP required during glycolysis?

-Fructose-6-phosphate –> fructose-1,6-bisphosphate
-Glucose –> glucose-6-phosphate
-Fructose-1,6-bisphosphate –> dihydroxyacetone phosphate + glyceraldehyde-3-phosphate
-Glucose-6-phosphate –> fructose-6-phosphate

A

-Fructose-6-phosphate –> fructose-1,6-bisphosphate
-Glucose –> glucose-6-phosphate

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96
Q

The process of ____ converts glucose into _____.

A

Glycolysis; pyruvate

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97
Q

Hexokinase is an example of a(n) _____ enzyme.

A

transferase

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98
Q

Which enzyme is responsible for splitting a hexose into 2 trioses?

-Enolase
-Phosphoglycerate mutase
-Phosphofructose isomerase
-Triose phosphate isomerase
-Aldolase

A

Aldolase

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99
Q

Which of the following is a potent activator of phosphofructokinase in mammals?

-Fructose-6-phosphate
-Glucose-6-phosphate
-Fructose-2,6-bisphosphate
-Fructose-1,6-bisphosphate
-Glyceraldehyde-3-phosphate

A

Fructose-2,6-bisphosphate

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100
Q

The active sites of aldolase contain a Lys residue that forms a(n) _____ and an Asp residue that participates in _____ reactions.

A

Schiff base; acid-base

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101
Q

Triose phosphate isomerase catalyzes a reaction that is most like that of _____.

A

Phosphoglucose isomerase

102
Q

Glyceraldehyde-3-PO4 is oxidized to _____, which can transfer a phosphate to _____.

A

1,3-bisphosphoglycerate; ADP

103
Q

Why is phosphoglycerate kinase still considered a kinase even though ADP is converted to ATP?

-The enzyme is freely reversible
-ATP is the ultimate source of the phosphate that is transferred to ADP
-The phosphate is transferred in conjunction with an oxidation reaction
-The reaction is metabolically irreversible
-None of the above

A

The enzyme is freely reversible

104
Q

ATP is required in which reaction?

A

Glucose –> glucose-6-phosphate (G6P)

105
Q

Which reaction is an oxidation reaction?

A

Glyceraldehyde-3-phosphate (GAP) –> 1,3-bisphosphoglycerate (BPG)

106
Q

In which reaction is at least one NADH formed?

A

Glycerol-3-phosphate (GAP) –> 1,3-bisphosphoglycerate (BPG)

107
Q

What type of enzyme is enolase, which catalyzes the conversion of 2-phosphoglycerate to phosphoenolpyruvate and water?

-Transferase
-Hydrolase
-Ligase
-Lyase
-Oxidoreductase

A

Lyase

108
Q

What sort of activity does fructose-1,6-bisphosphate have on pyruvate kinase?

-no effect
-competitive inhibitor
-noncompetitive inhibitor
-allosteric inhibitor
-activator

A

Activator

109
Q

Phosphofructokinase is allosterically _____ by high concentrations of _____.

A

-Inhibited by high concentrations of ATP
-Activated by high concentrations of fructose-2,6-bisphosphate

110
Q

Which metabolic conversion is considered the major control point of glycolysis?

A

Fructose-6-phosphate –> fructose-1,6-bisphosphate

111
Q

Which of the following is true regarding glycolysis?

-There is a net oxidation of substrate carbon atoms.
-There is no net release of free energy.
-Pyruvate is generated only during aerobic glycolysis
-There are 2 ATP formed for every 2 glucose molecules.

A

There is a net oxidation of substrate carbon atoms.

112
Q

The reaction catalyzed by the enzyme aldolase has a G degree prime ~ +23 kJ/mol. In muscle cells, the reaction proceeds in the same, forward direction. How can this occur?

-This G degree prime means it is thermodynamically favorable.
-The enzyme changes the delta G of the reaction in cells to something favorable.
-The concentration of reactant(s) must be significantly greater than product(s) in cells.
-The concentration of products(s) must be significantly greater than reactant(s) in cells.
-None of the above.

A

The concentration of reactant(s) must be significantly greater than product(s) in cells.

113
Q

Which of the following best describes the entry of mannose into glycolysis?

-Hydrolyzed into 2 glucose units, they enter normally
-Phosphorylated at C-1; UMP moiety transferred from UDP-glucose; epimerized at C-2; released from UMP moiety on next transfer as G1P
-Phosphorylated at C-1; UMP moiety transferred from UDP-glucose; epimerized at C-4; released from UMP moiety on next transfer as G1P
-Phosphorylated at C-6; epimerized at C-2 to produce G6P
-Phosphorylated at C-6; isomerized to produce F6P

A

Phosphorylated at C-6; isomerized to produce F6P

114
Q

What pathway is used to make glucose from other metabolites such as pyruvate or lactate?

-Glycogen synthesis
-Glycogen degradation
-Glycolysis
-Pentose phosphate pathway
-Gluconeogenesis

A

Gluconeogenesis

115
Q

How many equivalents of ATP are required to convert 2 molecules of pyruvate to glucose?

A

6

116
Q

Gluconeogenesis is most active in the ______.

-muscles
-brain
-heart
-liver
-kidneys

A

Liver

117
Q

Which of the following is true concerning the reaction catalyzed by pyruvate dehydrogenase?

-It is an oxidative decarboxylation.
-It is activated by high concentrations of ATP.
-The enzyme contains a pyridoxal phosphate prosthetic group.
-The reaction is an anaplerotic reaction because it can replace citric acid intermediates that are removed for other pathways.
-The enzyme contains two different types of subunits.

A

It is an oxidative decarboxylation.

118
Q

Which of the following is an inhibitor of pyruvate dehydrogenase?

-CoA
-Pyruvate
-FADH2
-NADH
-CO2

A

NADH

119
Q

Under aerobic conditions, pyruvate is converted to _____ by pyruvate dehydrogenase.

A

Acetyl-CoA

120
Q

What cellular location contains pyruvate dehydrogenase and most of the citric acid cycle enzymes?

-Cytosol
-Mitochondrial matrix
-Inner mitochondrial membrane
-Mitochondrial intermembrane space
-Outer mitochondrial membrane

A

Mitochondrial matrix

121
Q

Under anaerobic conditions in skeletal muscle, pyruvate is converted into _____.

A

Lactate

122
Q

Glycolysis forms _____ under either aerobic or anaerobic conditions.

A

ATP

123
Q

In skeletal muscle cells, oxidation of NADH generated from anaerobic glycolysis occurs during which reaction?

A

Pyruvate –> Lactate

124
Q

What is complex 1 of the electron transport chain?

A

NADH dehydrogenase I

125
Q

What is complex 2 of the electron transport chain?

A

Cytochrome c/ubiquinone oxidoreductase

126
Q

What is complex 3 of the electron transport chain?

A

Cytochrome c

127
Q

What is complex 4 of the electron transport chain?

A

Succinate dehydrogenase

128
Q

What is complex 5 of the electron transport chain?

A

Cytochrome oxidase

129
Q

What is complex 6 of the electron transport chain?

A

ATP synthase

130
Q

Which of the following enzymes catalyze oxidation reactions in the citric acid cycle?

-Succinate dehydrogenase
-Pyruvate dehydrogenase
-Glycerol-3-phosphate dehydrogenase
-Alpha-ketoglutarate dehydrogenase

A

-Succinate dehydrogenase
-Alpha-ketoglutarate dehydrogenase

131
Q

Both glycerophosphate and aspartate-malate shuttles are mechanisms to deliver electrons from _____ generated in the cytosol into the mitochondrial matrix.

-FADH2
-NADH
-Ubiquinone
-None of the above

A

NADH

132
Q

To reduce a molecular oxygen to water, complex IV takes ____ electrons from _____ copy/copies of cytochrome c.

-6,6
-8,8
-2,2
-4,4
-4,1

A

4,4

133
Q

ATP forms (is produced)

-upon transition from the loose to the tight form of the alpha and beta subunit complex of ATP synthase
-as a result of the flux of electrons through the channel formed by F0
-as a result of the positive ions pumped into the matrix of the mitochondrion

A

upon transition from the loose to the tight form of the alpha and beta subunit complex of ATP synthase

134
Q

Which citric acid cycle intermediate is replenished by the following anaplerotic reaction:
Carboxylation of pyruvate?

A

Oxaloacetate

135
Q

Which citric acid cycle intermediate is replenished by the following anaplerotic reaction:
Transamination of aspartate

A

Oxaloacetate

136
Q

Which citric acid cycle intermediate is replenished by the following anaplerotic reaction:
Transamination of glutamate

A

Alpha-ketoglutarate

137
Q

Which of the following is inhibited by carbon monoxide?

-NADH dehydrogenase
-ubiquinone
-cytochrome oxidase
-succinate dehydrogenase
-all of the above

A

Cytochrome oxidase

138
Q

In the citric acid cycle, what reduced cofactors are derived from the oxidation of one molecule of acetyl-CoA to two molecules of CO2?

-2 NADH and 1 FADH2
-3 NADH and 2 FADH2
-3 NADH and 1 FADH2
-2 NADH and 2 FADH2
-4 NADH and 2 FADH2

A

3 NADH and 1 FADH2

139
Q

In eukaryotes, the citric acid cycle occurs in the ____ and therefore requires that reactants of the citric acid cycle be transported from the _____.

-endoplasmic reticulum; mitochondrial matrix
-inner mitochondrial membrane; mitochondrial matrix
-outer mitochondrial membrane; cytosol
-cytosol; mitochondrial matrix
-mitochondrial matrix; cytosol

A

Mitochondrial matrix; cytosol

140
Q

The structure of ATP synthase changes in conformation because of ______.

-the rotation of the alpha and beta subunits
-the rotation of the beta subunit
-the rotation of ATP
-the rotation of the gamma subunit
-all of the above

A

The rotation of the gamma subunit

141
Q

The citric acid cycle is often described as amphibolic, because _____.

-it can operate both in the presence and absence of oxygen
-it can oxidize both carbons and nitrogens equally well
-it plays a role in both catabolism and anabolism
-it is both reversible and irreversible

A

it plays a role in both catabolism and anabolism

142
Q

______ is the end product of the citric acid cycle’s regeneration phase.

A

Oxaloacetate

143
Q

Select the three citric acid cycle intermediates replenished by anaplerosis in the order they enter the cycle.

A
  1. alpha-ketoglutarate
  2. succinyl-CoA
  3. Oxaloacetate
144
Q

Ethanol is oxidized to form acetate in the liver. Acetate is then converted to acetyl-CoA. How many molecules of ATP would be generated during the conversion of ethanol to acetate?

(Note: 2 mols of NADH are produced. assume 1 NADH is equivalent to 2.5 ATP and one FADH2 is equivalent to 1.5 ATP molecules).

A

15

145
Q

Which of the following enzymes catalyze oxidation reactions in the citric acid cycle?

-Succinate dehydrogenase
-Pyruvate dehydrogenase
-Glycerol-3-phosphate dehydrogenase
-Alpha-ketoglutarate dehydrogenase

A

-Succinate dehydrogenase
-Alpha-ketoglutarate dehydrogenase

(The reactions catalyzed by pyruvate dehydrogenase and glycerol-3-phosphate dehydrogenase are oxidation reactions, but they are not part of the citric acid cycle.)

146
Q

At which steps of the citric acid cycle are carbon atoms added to or removed from the reactants?

A

12, 14, and 15

(Reactions 14 and 15 are both decarboxylation reactions in which one carbon atom is lost from the substrate as CO2. In reaction 12, the two carbon atoms in the acetyl portion of acetyl-CoA are added to oxaloacetate.)

147
Q

If a suspension of mitochondria is mixed with Antimycin A which inhibits cyt b in complex iii, which among the following would increase in concentration?

-NAD
-Oxidized cytochrome c
-Reduced cytochrome c
-NADH
-Ubiquinol

A

NADH

148
Q

Match the following:

a.) 2,4-dinitrophenol
b.) cyanide
c.) cytochrome c
d.) complex ii
e.) chemiosmotic hypothesis

A

a.) 2,4-dinitrophenol: ATP synthase
b.) cyanide: complex IV
c.) cytochrome c: soluble electron carrier
d.) complex ii: succinate-CoQ oxidoredutase
e.) chemiosmotic hypothesis: Peter Mitchell

149
Q

The 4 complexes of the electron transport chain use the energy of electrons stored in reducing agents to create a concentration gradient of protons (H+) across the mitochondrial inner membrane. Give the number of protons pumped into the intermembrane space by each of the 4 complexes.

A

-Complex 1: 4
-Complex 2: 0
-Complex 3: 4
-Complex 4: 2

150
Q

Cyanide blocks electron transport through complex IV. Which of the following will occur if cyanide is added to cells?

-O2 consumption will decrease
-The rate of the citric acid cycle will increase
-NADH and FADH2 will be depleted
-ATP synthesis will increase

A

O2 consumption will decrease.

(Cyanide blocks electron transport. When this occurs, the consumption of oxygen decreases because oxygen is the final electron acceptor of the electron-transport process.)

(When electron transport is blocked, the concentrations of NADH and FADH2 in the cell increase, because they are no longer passing electrons to the electron transport chain. NAD+ and FAD become depleted.)

151
Q

If the transfer of electrons in tightly coupled mitochondria is inhibited between complex iii and complex iv, which of the following will occur?

-Oxygen consumption will increase
-The H+ ion concentration gradient will be dissipated.
-Electron transfer from NADH will stop
-The synthesis of ATP will increase

A

Electron transfer from NADH will stop.

(If the ETC is inhibited at any point, the transfer of electrons between all components of the chain ceases. Under these conditions, the re-oxidation of NADH ceases.)

(The movement of electrons through the ETC is linked with the movement of protons from the matrix across the inner mitochondrial membrane. Inhibition of ET will prevent formation of the proton gradient.)

152
Q

If the reduction potential for NAD+ is -0.315 V, for ubiquinone is 0.045 V, and for oxygen is 0.815 V, what is the potential for the oxidation of NADH and ubiquinol by oxygen?

A

1.13, 0.770

153
Q

What types of ATPase would perform:

Hydrolyzes ATP to pump ions to the outside of the cell

A

P-ATPase

154
Q

What types of ATPase would perform:

Synthesizes ATP in Archaea

A

A-ATPase

155
Q

What types of ATPase would perform:

Hydrolyzes ATP by means of a phospho-enzyme intermediate

A

P-ATPase

156
Q

What types of ATPase would perform:

Synthesizes ATP in eukaryotic respiration

A

F-ATPase

157
Q

What types of ATPase would perform:

Hydrolyzes ATP to acidify vacuoles

A

V-ATPase

158
Q

Which of the following statements regarding oxidative phosphorylation is TRUE?

-The rate of ATP synthesis depends on the magnitude of the proton electrochemical gradient.
-The smaller the electrochemical gradient, the faster the Pi-H+ symporter works
-Proton transfer through the F0 subunit of ATP synthase is required in order for ATP synthesis to occur.
-The addition of an uncoupler decreases the rate of reoxidation of NADH and FADH2, therefore decreasing the rate of the citric acid cycle.

A

Proton transfer through the F0 subunit of ATP synthase is required in order for ATP synthesis to occur.

(The addition of an uncoupler increases the rate of reoxidation of NADH and FADH2, by dissipating the H+ ion concentration gradient.)

159
Q

Which of the following are TRUE statements regarding the structure of ATP synthase?

-It has a membrane-embedded component called F0 and a component found in the matrix referred to as F1.
-The gamma subunit acts as the proton “wire” allowing equilibration of the ion gradient.
-Research indicates that the F1 portion of the protein rotates in a circular counterclockwise direction.

A

It has a membrane-embedded component called F0 and a component found in the matrix referred to as F1.

160
Q

The citric acid cycle is also called the _____.

A

Krebs cycle

161
Q

Which of the following describes the isomerization of citrate to isocitrate?

-a major regulatory step for the citric acid cycle
-an oxidation reaction
-the only unnecessary step of the citric acid cycle
-protects cells from the toxic effects of arsenite ion
-converts a tertiary alcohol that cannot easily be oxidized to a secondary alcohol that can be oxidized

A

Converts a tertiary alcohol that cannot easily be oxidized to a secondary alcohol that can be oxidized

162
Q

______ is the first compound that is oxidized in the citric acid cycle.

A

Isocitrate

163
Q

Which of the following enzymes catalyzes a substrate-level phosphorylation?

-malate synthase
-succinate dehydrogenase
-alpha-ketoglutarate dehydrogenase
-succinyl-CoA synthetase
-fumarase

A

Succinyl-CoA synthetase

164
Q

Which reaction produces GTP in the citric acid cycle?

isocitrate –> alpha-ketoglutarate

alpha-ketoglutarate –> succinyl CoA

succinyl CoA –> succinate

fumarate –> malate

malate –> oxaloacetate

A

succinyl CoA –> succinate

165
Q

The oxidation of succinate to fumarate is best characterized as an oxidation of ______.

-an alkane to an alkene
-an alcohol to an aldehyde
-an alcohol to a ketone
-an aldehyde to a carboxylic acid
-a beta-keto acid to CO2 and a carboxylic acid that is 1 carbon smaller

A

an alkane to an alkene

166
Q

The reaction catalyzed by fumarase is ______.

-isomerization of an alcohol
-a dehydration of an alcohol
-a hydroxylation of an alkene
-a hydration of an alkene
-none of the above

A

A hydration of an alkene

167
Q

How does the reaction catalyzed by malate dehydrogenase proceed despite a delta G degree prime of 29.7 kJ/ml?

-An elevated [H+] allows the reaction to proceed
-High levels of NAD+ allow the reaction to proceed
-Concentrations of oxaloacetate are kept very low by rapid use in the subsequent step
-The enzyme is unique in its ability to catalyze the reaction in only one direction
-The enzyme-catalyzed reaction under cellular conditions has a much smaller energy of activation

A

Concentrations of oxaloacetate are kept very low by rapid use in the subsequent step

168
Q

How many electrons are transferred from one acetyl group when it is converted to 2 carbon dioxide molecules in the citric acid cycle?

A

8

169
Q

Which of the following is inhibited by high levels of acetyl-CoA?

-malate dehydrogenase
-succinyl-CoA synthetase
-pyruvate carboxylase
-pyruvate dehydrogenase

A

pyruvate dehydrogenase

170
Q

An individual with a shortage of B vitamins (which include thiamine and riboflavin) may feel fatigued because of decreased pyruvate dehydrogenase activity. Which of the following would be true regarding this shortage?

-The amount of acetyl-CoA produced from carbohydrate metabolism that enters the citric acid cycle would be decreased
-A decrease in the amount of NADH would likely decrease the activity of citrate synthase.
-Flux through the citric acid cycle would cease until adequate pyruvate is available

A

The amount of acetyl-CoA produced from carbohydrate metabolism that enters the citric acid cycle would be decreased

171
Q

Which of the following represents a point of regulation for the citric acid cycle?

-pyruvate dehydrogenase complex
-aconitase
-isocitrate dehydrogenase
-fumarase

A

-pyruvate dehydrogenase complex
-isocitrate dehydrogenase

172
Q

Which of the following can be converted into glutamic acid in a single enzyme-catalyzed step?

-isocitrate
-oxaloacetate
-malate
-alpha-ketoglutarate
-succinyl-CoA

A

Alpha-ketoglutarate

173
Q

______ and pyruvate can be combined in an ATP-dependent reaction that regenerates one of the key intermediates in the citric acid cycle.

A

Carbon dioxide

174
Q

Which of the following uses intermediates of the citric acid cycle?

-gluconeogenesis
-amino acid biosynthesis
-fatty acid oxidation
-glycolysis

A

-gluconeogenesis
-amino acid biosynthesis

175
Q

The electrons formed from the aerobic oxidation of glucose are _____.

-ultimately transferred to O2 after several other transfer reactions
-transferred to the coenzymes NAD+ and FAD
-directly transferred to O2 during the citric acid cycle
-transferred to succinate and arachidonic acid

A

-ultimately transferred to O2 after several other transfer reactions
-transferred to the coenzymes NAD+ and FAD

176
Q

Which of the following statements is(are) true about oxidative phosphorylation?

-Electron transport provides energy to pump protons into the intermembrane space
-An electrochemical gradient is formed across the inner mitochondrial membrane
-Potassium and sodium ions form an ionic gradient across the inner mitochondrial membrane
-Complexes I, III, and IV actively transport protons into the intermembrane space during electron transport.

A

-Electron transport provides energy to pump protons into the intermembrane space
-An electrochemical gradient is formed across the inner mitochondrial membrane
-Complexes I, III, and IV actively transport protons into the intermembrane space during electron transport.

177
Q

In the electron transport chain, electrons are passed from redox center to redox center ______.

-spontaneously because of the redox potential gradient
-in an ATP-dependent fashion
-because of the addition of free energy
-because of the proton gradient
-with the assistance of a carrier protein

A

spontaneously because of the redox potential gradient

178
Q

In eukaryotes, the citric acid cycle occurs in the ______ and therefore requires that reactants of the citric acid cycle be transported from the ____.

A

mitochondrial matrix; cytosol

179
Q

Complexes I and II each transfer electrons to

A

Ubiquinone

180
Q

For every 2 electrons transferred from NADH to O, ______ protons are pumped from the matrix to the membrane.

A

10

181
Q

Electrons from FADH2 are delivered to _____, and electrons from NADH are delivered to _____ of the electron transport chain.

A

Complex II; Complex I

182
Q

The reduction potentials of all prosthetic groups of Complex I have reduction potentials between ____ and ____.

-NAD+; ubiquinone
-NADH; ubiquinol
-FAD; ubiquinone
-ubiquinone; oxygen
-ubiquinone; cytochrome c

A

NAD+; ubiquinone

183
Q

Which of the prosthetic groups listed can accept or donate either one or two electrons because of the stability of the semiquinone state?

-Cytochrome c
-NADH
-ubiquinone
-[2Fe-2S]
-Rieske center

A

ubiquinone

184
Q

Complex III accepts electrons from ____ and transfers them to ____.

-cytochrome c; cytochrome a
-ubiquinol; cytochrome c
-ubiquinone; cytochrome c
-ubiquinol; cytochrome b
-ubiquinone; cytochrome a

A

ubiquinol; cytochrome c

185
Q

How many protons are moved across the inner mitochondrial membrane at Complex III?

A

4

186
Q

Which of the following results from the first round of the Q cycle?

-2 reduced cytochrome c and 1 ubiquinone
-1 reduced cytochrome c and 1 ubiquinone
-1 reduced cytochrome c, 1 reduced cytochrome B, and 1 ubiquinone
-2 reduced cytochrome c and 1 ubiquinol
-1 reduced cytochrome c and 1 semiquinone

A

1 reduced cytochrome c and 1 semiquinone

187
Q

How many cytochrome c molecules are oxidized by Complex IV for each molecule of oxygen that is reduced?

A

4

188
Q

What is the terminal electron acceptor in aerobic organisms?

-NAD+
-FAD
-Ubiquinone
-varies from one organism to another
-none of the above

A

None of the above

189
Q

A poison that prevents the transfer of electrons from the last [Fe-S] cluster of Complex I to coenzyme Q is added to a suspension of actively respiring mitochondria. Which of the following will be observed?

-ATP production would be impaired due to the uncoupling of oxidative phosphorylation from electron transport
-ATP production would be reduced because of inhibition of the CoQ subunit of ATP synthase
-ATP production would be reduced because of a decrease in the number of protons pumped out of the mitochondrial matrix
-ATP production would be halted completely because of the block in electron transport through the electron transport chain
-ATP production would be maintained at the normal rate because of functional overlap between Complex I and Complex II.

A

ATP production would be reduced because of a decrease in the number of protons pumped out of the mitochondrial matrix

190
Q

Which conformation of the active sites in ATP synthase allows the binding of substrates?

-L state
-O state
-T state
-C state

A

L state

191
Q

Regarding the reactions of the citric acid cycle, you might expect the delta G of reactions in which CO2 is lost to be ______, the delta G of reactions utilizing transfer groups from CoA would be ______, and reactions such as isomerizations or hydrations would likely have _____ delta G values.

A

strongly negative; strongly negative; near zero

192
Q

_______ is the first compound that is oxidized in the citric acid cycle.

A

Isocitrate

193
Q

_____ catalyzes a substrate-level phosphorylation reaction within the citric acid cycle.

A

Succinyl-CoA synthetase

194
Q

In the net reaction of the citric acid cycle, what are the reactants?

A

3 NAD+ + FAD + GDP + Pi + acetyl-CoA

195
Q

Ubiquinone is a ____ molecule that serves as a ____ electron carrier

A

hydrophobic; 2

196
Q

Cytochrome c is a ____ molecule that serves as a _____ electron carrier.

A

hydrophilic; 1

197
Q

What enzymes perform this step of glycogenesis:

initiates glycogenesis by adding the first few glucose residues

A

Glycogenin

198
Q

What enzymes perform this step of glycogenesis:

performs the majority of glucose incorporation during glycogenesis

A

Glycogen synthase

199
Q

What enzymes perform this step of glycogenesis:

breaks off short chains of glycogen and reattaches them to form branches

A

Branching enzyme

200
Q

The function of the debranching enzyme can best be described as ______.

-it cleaves alpha(1–>6) bonds on glycogen through a hydrolysis reaction
-it cleaves alpha(1–>6) bonds on glycogen through a phosphorylsis reaction
-it transfers a set of 3 glucose residues from a branch and then cleaves the alpha(1–>6) bond through phosphorylysis
-it transfers a set of 3 glucose residues from a branch and then cleaves the alpha(1–>6) bond through hydrolysis

A

It transfers a set of 3 glucose residues from a branch and then cleaves the alpha(1–>6) bond through hydrolysis

201
Q

Glycoconjugates result from the covalent linkages of carbohydrates to lipids or ______.

-sphingolipids
-proteins
-amino acids
-nucleotides
-all of the above

A

proteins (notes say this)
amino acids (wiley says this)

202
Q

Glycogen synthase is activated by _____ and inactivated by ______

A

dephosphorylation; phosphorylation

203
Q

Glycogen phosphorylase is activated by ______ and inactivated by ____

A

phosphorylation; dephosphorylation

204
Q

Glycogen synthase and glycogen phosphorylase _______.

-can be activated simultaneously under all circumstances
-can be activated simultaneously under special circumstances
-can be activated simultaneously under no circumstances
-are modified by the same enzymes

A

-can be activated simultaneously under no circumstances
-are modified by the same enzymes

205
Q

Which molecule is used for the direct incorporation of glucose into glycogen during glycogenesis?

-sucrose
-UDP-glucose
-fructose-1,6-bisphosphate
-glucose-1-phosphate
-glucose-3-phosphate

A

UDP-glucose

206
Q

If an individual goes most of the day without eating, the glycogen synthase in their cells is likely to be ______, and thus in the ______ state, while glycogen phosphorylase is likely to be ______, and therefore in the ______ state. In this state, signal cascades activated by _____ are regulating the synthesis of breakdown of glycogen.

A

-phosphorylated
-inactive
-phosphorylated
-active
-glucagon

207
Q

Where are the two major sites for glycogen storage in humans?

A

Liver and muscle

208
Q

Which of the following statements is TRUE regarding glycogen synthase?

-It is activated by protein kinases
-It is activated by Ca2+ ions
-It catalyzes the formation of glycosidic bonds
-It uses glucose-1-phosphate as a substrate

A

It catalyzes the formation of glycosidic bonds

209
Q

Which of the following statements about glycogen is FALSE?

-It consists of glucose residues linked. by alpha(1-6)- and alpha(1-4)-glycosidic bonds
-It allows for the storage of many glucose molecules
-UDP-glucose is an “activated” compound that can donate a glucose molecule to a growing glycogen chain
-Glycogen signals are the fasting state and its released into the bloodstream when blood sugar levels are low

A

Glycogen signals are the fasting state and its released into the bloodstream when blood sugar levels are low

(Glucagon and NOT glycogen signals the fasting state. Glucagon is released from the pancreas into the bloodstream when blood sugar levels are low.)

210
Q

Which of the following is FALSE regarding glycogen?

-Branching enables more rapid breakdown of glycogen
-Glucose is stored as a polymer to reduce its chemical reactivity
-The main chain of the glycogen polymer predominantly contains glucose residues linked via 1-6 glycosidic bonds
-The first step in glycogen synthesis is catalyzed by hexokinase

A

The main chain of the glycogen polymer predominantly contains glucose residues linked via 1-6 glycosidic bonds

(The main chain of the glycogen polymer predominantly contains glucose residues linked via (1-4) glycosidic bonds.)

211
Q

The pentose phosphate pathway is divided into 2 phases, oxidative and nonoxidative. What are the respective functions of these two phases?

-to generate reducing equivalents for the other pathways in the cell; to generate ribose from other monosaccharides
-to generate ribose from other monosaccharides; to generate reducing equivalents for the other pathways in the cell
-to generate energy for nucleotide biosynthesis; to provide monosaccharides for nucleotide biosynthesis
-to provide monosaccharides for nucleotide biosynthesis; to generate energy for nucleotide biosynthesis

A

to generate reducing equivalents for the other pathways in the cell; to generate ribose from other monosaccharides

212
Q

Which substrate regulates flux through the pentose phosphate pathway?

-NAD+
-Glucose-6-phosphate
-Ribose-5-phosphate

A

NAD+

213
Q

NADPH used in lipid biosynthesis is produced by the ______ pathway.

A

pentose phosphate

214
Q

The oxidative portion of the pentose phosphate pathway generates two molecules of _____ for each molecule of G6P

A

NADPH

215
Q

Ru5P is converted to Xu5P by ribulose-5-phosphate ______.

A

epimerase

216
Q

Where in a cell would you find this glycoconjugate:
glycoprotein

A

Extracellular matrix

217
Q

Where in a cell would you find this glycoconjugate:
glycolipid

A

Cell membrane

218
Q

Where in a cell would you find this glycoconjugate:

proteoglycan

A

Extracellular matrix

219
Q

Where in a cell would you find this glycoconjugate:
peptidoglycan

A

Cell wall

220
Q

Liver and muscle are associated with

A

Glycogen storage

221
Q

Elastin is associated with

A

proline and glycine

222
Q

Glucuronic acid and N-acetylglucosamine are associated with

A

Hyaluronic acid

223
Q

Bacterial cell wall is associated with

A

Peptidoglycans

224
Q

Collagen is associated with

A

left-handed helix

225
Q

The main component of a bacterial cell wall is a

A

peptidoglycan

226
Q

N-linked oligosaccharides can be covalently linked to proteins at which amino acid?

A

Asn

227
Q

Vitamin C (ascorbic acid) is required for the hydroxylation of _____ during collagen synthesis.

A

proline

228
Q

What is the correct order of intermediates during the synthesis of glycogen?

A

glucose –> glucose-6-phosphate –> glucose-1-phosphate –> UDP-glucose –> glycogen

229
Q

Which enzyme below is not required for the synthesis of branched glycogen?

-glycogen phosphorylase
-glycogen synthase
-branching enzyme
-phosphoglucomutase
-All are required for the synthesis of glycogen

A

glycogen phosphorylase

230
Q

The main enzyme of glycogen catabolism is ____, which catalyzes a _____ reaction.

A

glycogen phosphorylase; phosphorolysis

231
Q

Which of the following statements about glycogen is true?

-Glycogen is a polymer of glucose in a(1–>6) linkages with a(1–>4) linked branches every 8-14 residues
-UDP-glucose is produced from glycogen by the action of the enzyme phosphorylase
-In glycogen breakdown. glucose residues are sequentially removed from the nonreducing ends
-The breakdown of glycogen in skeletal muscle ultimately supplies glucose-6-phosphate, which can enter glycolysis to generate ATP

A

-In glycogen breakdown. glucose residues are sequentially removed from the nonreducing ends
-The breakdown of glycogen in skeletal muscle ultimately supplies glucose-6-phosphate, which can enter glycolysis to generate ATP

232
Q

The glycogen debranching enzyme is required for ______.

-the transfer of 3-glucose units from one branch to another
-the transfer of phosphate from one position to another
-cleaving alpha(1–>6) sugar linkages

A

-the transfer of 3-glucose units from one branch to another
-cleaving alpha(1–>6) sugar linkages

233
Q

A deficiency in muscle glycogen phosphorylase would result in _____.

-normal muscle glycogen structure
-abnormal muscle glycogen structure
-elevated muscle glycogen levels

A

-normal muscle glycogen structure
-elevated muscle glycogen levels

234
Q

Which of the following requires large amounts of ribose-5-phosphate?

-DNA synthesis
-amino acid synthesis
-lipid synthesis
-glycogen synthesis
-cholesterol synthesis

A

DNA synthesis

235
Q

For each molecule of glucose-6-phosphate that enters the oxidative phase of the pentose phosphate pathway, _____ NADPH and _____ CO2 are produced.

A

2; 1

236
Q

Which of the following enzymes catalyzes an oxidative decarboxylation reaction?

-glucose-6-phosphate dehydrogenase
-glyceraldehyde-3-phosphate dehydrogenase
-glycogen dehydrogenase
-6-phosphogluconate dehydrogenase

A

6-phosphogluconate dehydrogenase

237
Q

In the conversion of ribulose-5-phosphate to glycolytic intermediates, which of the following enzymes is used?

-phosphoglucomutase
-transketolase
-phosphoglycerate mutase
-phosphofructoisomerase

A

transketolase

238
Q

In the ABO blood type system, how many monosaccharides are found in each of the oligosaccharides for the various blood types?

A

A: 6
B: 6
O: 5

239
Q

In a ____, the carbohydrate is responsible for most of the mass

A

proteoglycan

240
Q

In a ____, the protein is responsible for most of the mass

A

Glycoprotein

241
Q

Bacterial cell walls are made of ____.

A

Peptidoglycans

242
Q

Is glycogen a reducing sugar? Explain.

A

No, glycogen lacks the free aldehyde necessary to reduce copper.

243
Q

Why does the pentose phosphate pathway take place in the cytosol?

-The reagent NAD+ is only found in the cytosol
-The pentose phosphate pathway takes place in the endoplasmic reticulum
-If it took place in mitochondria, it would compete with other metabolic pathways found there
-Substrates for other pathways in which carbohydrates are metabolized are found in the cytosol

A

Substrates for other pathways in which carbohydrates are metabolized are found in the cytosol

244
Q

Which of the following enzymes directly converts phosphorylase b into the more active form, phosphorylase a?

-cAMP-dependent protein kinase
-phosphorylase kinase
-protein kinase A
-adenylate cyclase
-phosphoprotein phosphatase -1

A

phosphorylase kinase

245
Q

In the event that NADPH is needed but not ribose, which of the following is an end product of the pentose phosphate pathway?

-ribulose-5-phosphate
-dihydroxyacetone phosphate
-fructose-1,6-bisphosphate
-1,3-bisphosphoglycerate
-glyceraldehyde-3-phosphate

A

glyceraldehyde-3-phosphate

246
Q

The helical structure of collagen contains ______.

-3 right-handed helices wound around each other in a right-handed triple helix
-3 right-handed helices wound around each other in a left-handed triple helix
-3 left-handed helices wound around each other in a left-handed triple helix
-3 left-handed helices wound around each other in a right-handed triple helix

A

3 left-handed helices wound around each other in a right-handed triple helix

247
Q

Levels of G6P are affected by which of the following?

-glycogen breakdown
-the activity of the pentose phosphate pathway
-galactose preparation for entry into glycolysis

A

All of the above

248
Q

Which of the following requires large amounts of ribose-5-phosphate?

-amino acid synthesis
-lipid synthesis
-cholesterol synthesis
-DNA synthesis
-glycogen synthesis

A

DNA synthesis

249
Q

Initiation of glycogen biosynthesis with the isomerization of glucose-6-phosphate to glucose-1-phosphate by the enzyme ______.

A

phosphoglucomutase

250
Q

The pentose phosphate pathway is divided into two phases, oxidative and nonoxidative. What are the respective functions of these two phases?

-to generate ribose from other monosaccharides; to generate reducing equivalents for other pathways in the cell
-to generate energy for nucleotide biosynthesis; to provide monosaccharides for nucleotide biosynthesis
-to provide monosaccharides for nucleotide biosynthesis; to generate energy for nucleotide biosynthesis
-to generate reducing equivalents for the other pathways in the cell; to generate ribose from other monosaccharides
-to provide monosaccharides for amino acid biosynthesis; to generate reducing equivalents for other pathways in the cell

A

To generate reducing equivalents for the other pathways in the cell; to generate ribose from other monosaccharides

251
Q

What is the selective advantage of living in a biofilm?

-It provides no selective advantage
-It generates a stable environment
-It extracts nutrients more efficiently from the substrate
-Bacteria in biofilms grow faster
-It ensures that only a single species can grow in a given space

A

It generates a stable environment

Biochemistry (5 decks)

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