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Biochemistry > Most Missed Questions throughout the year > Flashcards

Most Missed Questions throughout the year Flashcards

1
Q

Which of the following is activated by ADP?
- aconitase
-isocitrate dehydrogenase
- malate dehydrogenase
- succinyl-CoA synthetase
- citrate synthase

A

Isocitrate dehydrogenase

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2
Q

where is succinate dehydrogenase located

A

mitochondrial inner membrane

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3
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

A

3 NADH
1 QH2

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4
Q

Which of the following enzymes catalyzes a substrate-level phosphorylation?
- fumarase
-succinate dehydrogenase
- alpha-ketoglutarate dehydrogenase
- succinyl-CoA synthetase
- malate synthase

A

succinyl-CoA sysnthetase

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5
Q

Which of the following is correct concerning the reaction catalyzed by pyruvate dehydrogenase?
- reaction is anaplerotic since it can replace citric acid intermediates that are removed for other pathways
- it is activated by high concentrations of ATP
-the enzyme contains a pyridoxal phosphate prosthetic group
-the enzyme contains two different types of subunits
- it is an oxidation decarboxylation

A

it is an oxidation decarboxylation

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6
Q

what citric acid cycle enzyme is not used in the glyoxylate cycle?

A

isocitrate dehydrogenase

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7
Q

The mechanism of malate synthase that catalyzes the conversion of glyoxylate and acetyl-CoA to malate would be most similar to which citric acid cycle enzyme?

A

citrate synthase

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8
Q

Which of the following has the most spontaneous hydrolysis?
-pyrophosphate
-glucose-1-phosphate
-phosphocreatine
-1,3-bisphosphoglycerate
-phosphoenolpyrubate

A

phosphoenolpyruvate

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9
Q

Which of the following contains a high energy bond that is used for a substrate-level phosphorylation in glycolysis?
-acetyl phosphate
-1,3-bisphosphoglycerate
-2,3-bisphosphoglycerate
-1-phosphoglycerate
-fructose-1,6-bisphosphate

A

1,3-bisphosphoglycerate

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10
Q

Which of the following is a potent activator of phosphofructokinase in mammals?
- fructose-6-phosphate
-fructose-2,6-bisphosphate
-glucose-6-phosphate
-fructose-1,6-bisphosphate
-glyceraldehyde-3-phosphate

A

fructose-2,6-bisphosphate

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11
Q

Fructose-2,6-bisphosphate is an activator of ____ and an inhibitor of _____

A

phosphofructokinase
fructose bisphosphatase

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12
Q

what would occur if both phosphofructokinase and fructose bisphosphatase were active simultaneously

A

futile cycle

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13
Q

gluconeogenesis is most active in the

A

liver

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14
Q

which enzyme below is not required for the synthesis of branched glycogen?
-glycogen synthase
-glycogen phosphorylase
-branching enzyme
-all are required for synthesis of glycogen

A

glycogen phosphorylase

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15
Q

Correct order of intermediates during the synthesis of glycogen

A

glucose
glucose-6-phosphate
glucose-1-phosphate
UDP-glucose
Glycogen

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16
Q

What two molecules are used in the synthesis of sphingosine

A

palmitic acid and serine

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17
Q

which of the following alcohols is esterfied to the phosphate group of glycerophospholipids?
-glycerol
-choline
-serine
-ethanolamine
-all of the above

A

all of the above

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18
Q

what are the characteristics of most unsaturated fatty acids found within a human cell

A

deprotonated carboxylic acid and cis double bonds

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19
Q

which of the following molecules is in the most reduced state?
-methane
-formaldehyde
-formic acid
-carbon dioxide
-methanol

A

methane

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20
Q

Which of the following is more oxidized than acetaldehyde?
-ethane
-ethylene glycol
-ethanol
-ethylene
-acetic acid

A

acetic acid

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21
Q

which of the following factors contributes to the highly exergonic nature of ATP hydrolysis?
- addition of water to the hydrophilic ATP molecule
-decrease in negative-ion repulsion in ATP
-removal of phosphate from cytoplasm
-low energy activation for the hydrolysis
-none of the above

A

decrease in negative-ion repulsion

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22
Q

which of the following describes glycosaminoglycans?
-bound to other proteins to minimize interactions with water
-associated with the cytoskeleton
-homopolymer composed of only one type of monosaccharide
-found in extracellular space
-none of the above

A

found in extracellular space

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23
Q

Which of the disaccharides has both anomeric carbons involved in the glycosidic bond?

A

sucrose

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24
Q

which fatty acid is commonly attached to soluble proteins to allow membrane localization?

A

myristic acid

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25
Q

Of the major lipoproteins, _____ are highest in cholesterol and cholesterol esters while ____ are highest in triacyclglycerols

A

LDL
chylomicrons

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26
Q

during beta oxidation in the peroxisome, what reoxidizes the enzyme-bound FADH2 during the first oxidation of the pathway

A

O2

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27
Q

When the transaminase enzyme is in the _____ form, it will only react with _____

A

pyridoxal
alpha amino acids

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28
Q

They hydrolysis of triaclglycerols stored in adipose tissue is catalyzed by the enzyme

A

hormone-sensitive lipase

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29
Q

For every two electrons transferred from NADH to oxygen, ____ protons are pumped from the matrix to the intermembrane space

A

10

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30
Q

what enzyme is the major control point of cholesterol synthesis in humans

A

HMG-CoA reductase

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31
Q

Which of the following statements describes integral membrane proteins?
-association with the membrane is through an attached fatty acyl or prenyl group
-easily removed by changes in pH or high salt
-tend to be water soluble
-never completely span the lipid bilayer
-amino acids that contact the core of the membrane are hydrophobic

A

amino acids that contact the core of the membrane are hydrophobic

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32
Q

after depolarization of a nerve cell, what event restores the resting potential

A

K+ influx

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33
Q

D-glucose and D-Mannitol are similarly soluble, but D-Glucose is transported through the erythrocyte membrane four times as rapidly as D-Mannitol. What is a likely explanation

A

D-glucose and D-Mannitol are transported via a system that distinguishes the two sugars

34
Q

Ubiquinone is a _____ molecule that serves as a _____ electron carrier, cytochrome c is a _____ molecule that serves as a _____ electron carrier

A

hydrophobic
2
hydrophilic
1

35
Q

what free radical is thought to be commonly produced by the electron transport chain

A

superoxide, O2

36
Q

in the electron transport chain, electrons are passed from redox center to redox center _____

A

spontaneously because of redox potential gradient

37
Q

to oxidize fatty acids in a triacylglycerol, what must occur first

A

lipolysis

38
Q

in the beta oxidation pathway, the oxidation occurs at carbon _____ with the acetyl group that becomes acetyl-CoA from the ____ end of the fatty acid

A

3
carbonyl

39
Q

how many photons of light must be absorbed by photosystem II to produce one molecule of oxygen

A

4

40
Q

All are properties of uncouplers EXCEPT?
-they dissipate the proton gradient
-ATP/ADP ratio increases
-electron transport continues
-they were briefly used as wight-loss drugs
-heat is produced

A

ATP/ADP ratio increases

41
Q

Which of the following is not a strategy for the regulation of metabolic pathway?
-allosteric enzymes
-all of these are strategies
-feedback inhibition
-competing pathways are located in the same organelle
-covalent modification of enzymes

A

competing pathways are located in the same organelle

42
Q

In bacteria, translation of the mRNA begins

A

during the synthesis of mRNA

43
Q

Which of the following is true?
- the peptide bonds in the beta-sheet are extended
-the peptide bonds in the alpha-helix coil spiral to interact with themselves
-both alpha-helixes and beta-sheets can be found as part of tertiary structure
-all of these

A

all of these

44
Q

In the mitochondrial matrix of muscle cells, the pH is 7.9. Outside of resting muscle cells, the pH is 7.4. During intense exercise, the pH outside the muscle cell can fall to pH 6.9. Estimate the difference in [H+] (proton concentration) between the mitochondrial matrix and outside of muscle cell during intense exercise

A

10 fold higher [H+] outside of muscle cell

45
Q

All are properties of DNA polymerase III EXCEPT:
-it synthesizes most of the leading strand prior to aiding in the synthesis of the lagging strand
-it is responsible for incorporating most of the nucleotides in the lagging strand
-it contains a 3’ to 5’ exonuclease activity
-it is a large protein complex containing more than five subunits
-much greater processivity than DNA polymerase I

A

It synthesized most of the leading strand prior to aiding in the synthesis of the lagging strand

46
Q

Electron flow in the mitochondria follows what pathway

A

Both complex I->III->IV and complex II->III->IV

47
Q

A recombinant plasmid has been derived from pBR322 by inserting DNA into the EcoRV site, for expressing a protein from the recombinant gene. Which of the following are not true of the resulting plasmid?
-The question cannot be answered, since it is unlikely that the protein will be expressed at all, because there is no promoter for mRNA synthesis
-the protein is not likely to be biologically active without some further treatment
-replication of the new plasmid will be eliminated
-the plasmid will be resistant to ampicillin
-the protein will probably contain some extra AA on its N-terminal end

A

Replication of the new plasmid will be eliminated

48
Q

Which of the following is not required for the elongation phase of protein synthesis?
-mRNA
-fmet-tRNAfmet
-GTP
-peptidyl transferase

A

fmet-tRNAfmet

49
Q

Most of the oxygen carried by hemoglobin and myoglobin is used in which essential metabolic process

A

electron transport at complex IV (cytochrome oxidase)

50
Q

The three dimensional structure of nucleic acids can include all except
-hairpin loops
-supercoiling
-base stacking
-circular molecules
-all of these can be included in the three dimensional structure

A

all of these can be included in the three dimensional structure

51
Q

All occur during DNA replication in E. coli EXCEPT:
-DNA polymerase I hydrolyzes RNA from the 5’ ends of Okazaki fragments
-helicase unwinds dsDNA at the replication fork
-primase (DnaG) acts mainly at the GC-rich origin of replication of the chromosome
-DNA ligase catalyzes the formation of phosphoester bonds on the lagging strand
-all are true

A

Primase (DnaG) acts mainly at the GC-rich origin of replication of the chromosome

52
Q

Replication of eukaryotic DNA

A

must be coordinated in time with the cell cycle

53
Q

Which of these amino acids can be converted by a transaminase
-alanine
-aspartate
-glutamate
-all three of them
-only b and c

A

all three of them

54
Q

Which of the following statements concerning RNA transcription is false?
-DNA strands become separated during synthesis
-all 4 ribonucleotides are required
-the template strand is read in the 3’ to 5’ direction
-a primer is required for RNA synthesis
-Synthesis of RNA is as accurate as synthesis of DNA

A

a primer is required for RNA synthesis
and
synthesis of RNA is as accurate as synthesis of DNA

55
Q

The Bohr effect on oxygen binding states is evident during exercise as this characteristic

A

as the pH goes down, Hb binds oxygen less tightly

56
Q

Which pathway is central to virtually all living organisms, regardless of their main source of food (carbon source)?

A

citric acid cycle

57
Q

Which of the following is involved in regulation of eukaryotic transcription?
-Histone acetyltransferase
-chromatin remodeling complexes
-histone deacetylase
-methylated cytosines
-all of these choices

A

all of these choices

58
Q

Initiation of transcription in eukaryotes is primarily controlled

A

in the formation of the preinitiation complex

59
Q

Which of the following is not true?
-the synthesis of ATP in mitochondria is driven by a proton or pH gradient
-synthesis of ATP is directly linked to the oxidation of NADH
-the reoxidation of NADH and FADH2 indirectly creates a proton gradient that is involved in ATP synthesis
-all of this is true

A

the synthesis of ATP is directly linked to the oxidation of NADH

60
Q

Migration of DNA during electrophoresis is based

A

mostly on the size of the molecule, since the ratio of charge to mass is approximately the same, no matter how large the DNA is

61
Q

What is the charge on the peptide Met-Lys-Glu-Ala-Asp at pH 7

A

-1

62
Q

Elongation factor Tu (EF-Tu) binds

A

aminoacyl-tRNA in the presence of GTP

63
Q

Digestion of plasmid DNA with a restriction enzyme has produced ‘sticky ends’. The sticky ends

A

are able to form base pairs with each other

64
Q

All of the following are characteristics of replication of the E. coli circular chromosome EXCEPT
-torsional stress introduced in the duplex DNA is relieved by DNA gyrase
-the unwinding of the duplex DNA is driven by the translocation of the DNA polymerase
-replication forks move in opposite directions
-replication is bi-directional
-it initiates at a unique position called an origin of replication

A

The unwinding of the duplex DNA is driven by the translocation of the DNA polymerase

65
Q

DNA polymerases share all of the following characteristics EXCEPTS:
-polymerization is antiparallel to template strand
-polymerization proceeds in a 5’-3’ direction
-polymerization is dependent upon the presence of an oligonucleotide primer
-incoming bases are paired with corresponding bases on the template strand within the polymerase active site
-5’-3’ error-coding activity

A

5’-3’ error-coding activity

66
Q

The reactions where glucose is converted to glucose 6-phosphate and fructose 6-phosphate is converted to fructose 1-6-bisphosphate are examples of
-priming reactions
-phosphorylation reactions
-exergonic reactions
-kinase reactions
all of these

A

all of these

67
Q

which of the following best describes the order of events at the promotor
- open complex- transcription initiation-closed complex
-transcription initiation-open complex-closed complex
-closed complex-open complex-transcription initiation
-open complex-closed complex-transcription initiation

A

closed complex-open complex-transcription initiation

68
Q

Aw what point does the sigma subunit of RNA polymerase released from the core enzyme

A

after transcription begins and about 5 nucleotides have been added to the RNA chain

69
Q

What is the pH of a solution that contains three parts of acetic acid and one part sodium acetate? The pK for acetic acid is 4.76

A

4.28

70
Q

At pH 4, how many charged groups are present in the pentapeptide Ala-Asp-His-Ser-Lys

A

+2

71
Q

The formation of a dipeptide form two amino acids requires

A

loss of water

72
Q

lysine can form a salt bridge by interacting with the side chain of

A

Glu

73
Q

Of all the species that enzymes bind, they are thought to bind most tightly to

A

transition states

74
Q

What does the K1 for a competitive inhibitor mean?

A

tighter binding to ES complex

75
Q

What is most critical for maintaining the tertiary structure of a protein

A

Hydrophobic interactions

76
Q

Heme is considered a

A

prosthetic group

77
Q

An organic molecule that is tightly bound to an enzyme and participates in an enzyme catalyzed reaction is specifically referred to as a

A

prosthetic group

78
Q

Ascorbic acid is required for the production of ____ in collagen

A

hydroxyproline

79
Q

Proper expression for Michaelis-Menton equation

A

V= Vmax [S] over Km+[S]

80
Q

Metabolic acidosis often causes increased respiratory rates. What portion of the bloodstream buffer is lost through increased respiration

A

CO2

Biochemistry (14 decks)

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