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Biochemistry > Test > Flashcards

Test Flashcards

1
Q

CDP-diacylglycerol is Not involved in the biosynthesis of:

A

Sphingomyelin

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2
Q

In which cellular compartment are ketone bodies synthesized?

A

The mitochondrial matrix

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3
Q

Facilitated diffusion through a biological membrane is:
A) An endergonic process
B) generally irreversible
C) Not specific with respect to the substrate
D) Drive by energy supplied ATP
E) Driven by a difference of solute concentration across the membrane.

A

E) Driven by a difference of solute concentration across the membrane.

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4
Q

Disulfide bonds are more likely to be formed____of the cell, due to the _____ environment there.

A

outside; oxidizing

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5
Q

Which tissue cannot use ketone bodies as a fuel?

A

Liver

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6
Q

Which statement is true concerning the chloride-bicarbonate exchanger?
A) The transporter is electrogenic, and the exchanger is a passive anti porter.
B) The exchanger is a passive symporter
C) The protein decreases the carbon dioxide-carrying capacity of the bloodstream.
D) The exchanger is a passive anti porter, and it increases the carbon dioxide-carrying capacity of the bloodstream.
E) The transporter is electrogenic.

A

D) The exchanger is a passive anti porter, and it increases the carbon dioxide-carrying capacity of the bloodstream.

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7
Q

Which statement is NOT true regarding the oxidation of one molecule of palmitate(16) by the-beta-oxidation pathway?

A

Eight molecules of FADH2 are formed.

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8
Q

The reaction catalyzed by which enzyme is NOT linked to the reduction of NAD?

A

succinate dehydrogenase

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9
Q

The functional differences, as well as differences in three-dimensional structures, between two different enzymes from E.coli result directly from their different:

A

Amino acid sequences.

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10
Q

Which statement is false regarding ladderanes?

A

Ladderanes are classified as phospholipids.

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11
Q

CO binds more strongly to the heme iron than O2 does due to which reason?
A) All of the answers are correct.
B) CO binds to the heme iron perpendicular to the porphyrin ring, allowing maximum electron orbital overlap between CO and Fe2+.
C) CO weighs less than O2, therefore binding to the heme iron more easily
D) None of the answers are correct.
E) CO binds to the heme iron covalently, while O2 binds via ionic interaction.

A

B) CO binds to the heme iron perpendicular to the porphyrin ring, allowing maximum electron orbital overlap between CO and Fe2+.

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12
Q

Which compound cannot serve as the starting material for the synthesis of glucose via gluconeogenesis?

A

Acetate

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13
Q

Biological oxidation-reduction reactions never involve:

A

Formation of free e-.

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14
Q

Which statement is false with respect to the pyruvate dehydrogenase complex?
A) Its activity is increased in the presence of coenzyme A and ADP
B) The proximity of the catalytic enzymes in the cluster slows down the overall rate.
C) It is located in the mitochondrial matrix
D) Its activity is increased in the presence of Ca2+ ions in skeletal muscle

A

B) The proximity of the catalytic enzymes in the cluster slows down the overall rate.

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15
Q

Why is an anaerobic fate of pyruvate necessary in skeletal muscle?
A) It allows for the deoxidation of NADH to NAD+, as NAD+ is in limited supply during anaerobic conditions.
B) It is required to maintain the reducing environment of the cytosol.
C) None of the answers are correct.
D) It decreases the pH of the skeletal muscle cell, thereby increasing release of oxygen from myoglobin.
E) The anaerobic process directly generates additional ATP for working muscle tissue.

A

A) It allows for the deoxidation of NADH to NAD+, as NAD+ is in limited supply during anaerobic conditions.

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16
Q

Chylomicrons carry ______ in the ______.

A

triacylglycerols;blood

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17
Q

Glycogen phosphorylase removes glucose (as glucose 1-phosphate) from the ______ ends of glycogen chains until it is ________ a branch point.

A

nonreducing; four glucose units from

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18
Q

When the DG of the ATP synthesis reaction is measured on the surface of the ATP synthase enzyme, it is found to be close to zero. This is thought to be due to:
A) A very low energy of activation.
B) stabilization of ATP relative to ADP by enzyme binding.
C) An offset of the enthalpy of the reaction by the entropy change.
D) Enzyme-induced oxygen exchange.

A

B) stabilization of ATP relative to ADP by enzyme binding.

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19
Q

Which mutation would be MOST likely to result in amyloid formation?

A

Lys—>Phe

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20
Q

The hormones epinephrine and norepinephrine are derived biosynthetically from:

A

Tyrosine.

21
Q 
Titration of valine by a strong base, for example NaOH, reveals two pK’s. Which is the titration reaction occurring at pK2 (pk2=9.62)?
A) —NH3+ +OH- —> -NH2 + H2O
B) -COOH + OH- —> —COO- + H2O
C)-NH2 + OH- —> —NH- + H2O
D) -COO- + NH2+ —> —COOH + —NH2
E) -COOH + NH2 —> —COO- + NH2+
A

A) —NH3+ +OH- —> -NH2 + H2O

22
Q

Which statement is false regarding biological oxidation?
A) Oxidation can occur by addition of oxygen to a molecule.
B) Electrons are transferred from substances with a high reduction potential to substances with a lower reduction potential.
C) Oxidases, oxygenases, and dehydrogenase are all enzymes that catalyze biological oxidation-reduction reactions.
D) NAD+ is a cosubstrate of certain dehydrogenase and always accepts electrons in the form of hydride ions.

A

B) Electrons are transferred from substances with a high reduction potential to substances with a lower reduction potential.

23
Q

Treatment of methanol poisoning by using ethanol is an example of what type of enzyme inhibition?

A

Competitive.

24
Q

Which compound is NOT an intermediate of the citric acid cycle?

A

acetyl-CoA

25
Q

The role of an enzyme in an enzyme-catalyzed reaction is to:

A

Increase the rate at which substrate is converted into product.

26
Q

Coenzyme Q is a prosthetic group for which complex in the electron-transfer chain?
A) None of the above; Q is in the lipid bilayer of the inner mitochondrial membrane.
B) Complex I
C) Complex III
D) Complex II

A

A) None of the above; Q is in the lipid bilayer of the inner mitochondrial membrane.

27
Q

In solution at pH 6.5, palmitate has an overall negative charge. This means that the pKa of palmitate is:

A

<6.5

28
Q

In mammals, what process does NOT occur during the citric acid cycle?

A

net synthesis of oxaloacetate from acetyl-CoA.

29
Q

Which enzymes are NOT among the seven internationally accepted classes of enzymes?

A

polymerases.

30
Q

Which compound is NOT an intermediate in the synthesis of Ianosterol from acetyl-CoA?

A

Malonyl-CoA

31
Q

Glu residues tend to disrupt an alpha helix when they occur next to each other in a protein at pH 7.0 because:
A) Covalent interactions may occur between the Glu side chains.
B) The R groups of Glu can form a hydrogen bond with each other.
C) Glu is highly hydrophobic, awhich destabilizes the helix.
D) Electrostatic repulsion occurs between the Glu side chains.
E) Glu adds too much conformational flexibility for helix formation.

A

D) Electrostatic repulsion occurs between the Glu side chains.

32
Q

The pKas’ of arginines alpha-carboxyl group, alpha-amino group, and side chain are 1.8, 9.0, and 12.5 respectively. What is arginines pI?

A

10.8

33
Q

Which atom is a common electrophile?

A

phosphorus of a phosphate group

34
Q

Which list correctly shows bond/interaction strength in decreasing order (strongest to weakest)?

A

covalent bond> ionic bond> hydrogen bond> van der waals interactions

35
Q

Which type of enzyme is responsible for attaching phosphate groups to specific amino acids?

A

A protein kinase.

36
Q

What mechanism accounts for mitochondrial inheritance in sexual reproduction in animals?

A

Male mitochondria are degraded after fertilization.

37
Q

Glycolysis is the name given to a metabolic pathway occurring in many different cell types. It consists of 11 enzymatic steps that convert glucose to lactic acid. glycolysis is an example of:

A

Fermentation.

38
Q

Which type of structure refers to particularly stable arrangements of amino acid residues in a protein that give rise to recurring patterns?

A

Secondary structure.

39
Q

Which answer choice is the BEST description of the benefits that are provided by the extended conformation that the heteropolysaccharide glycosaminoglycans assume in solution?
A) The repulsive forces of densely packed negative charges are minimized, and the hydrophobic portions of the molecule may pack closely together to maximize van der Waals forces.
B) The patterns of sulfated and non sulfated sugar residues are more easily recognized by their respective ligands.
C) The repulsive forces of densely packed negative charges are minimized, and the patterns of sulfated and non sulfated sugar residues are more easily recognized by the respective ligands.
D) The hydrophobic portions of the molecule may pack closely together to maximize van de Waals forces.
E) The repulsive forces of densely packed negative charges are minimized.

A

C) The repulsive forces of densely packed negative charges are minimized, and the patterns of sulfated and non sulfated sugar residues are more easily recognized by the respective ligands.

40
Q

Which statement is generally true of integral membrane proteins?
A) The domains that protrude on the cytoplasmic face of the plasma membrane nearly always have covalently attached oligosaccharides.
B) They undergo constant motion that moves a given domain from the outer face of a membrane to the inner face and then back to the outer.
C) The secondary structure in the transmembrane region consists solely of alpha helices or beta sheets.
D) They are usually susceptible to degradation by trypsin
E) They can be removed from the membrane with high salt or mild denaturing agents.

A

C) The secondary structure in the transmembrane region consists solely of alpha helices or beta sheets.

41
Q

Which process does NOT involve the fusion of two membranes or two regions of the same membrane?

A

Entry of glucose into cells.

42
Q

Which statement applies to synthesis of malonyl-CoA?
A) The three step synthesis is irreversible.
B) The reaction is catalyzed by acetyl-CoA carboxylase.
C) All of the statements apply to the synthesis of malonyl-CoA.
D) It is synthesized from acetyl-CoA and bicarbonate
E) In animal cells the synthesis takes place in the cytoplasm.

A

C) All of the statements apply to the synthesis of malonyl-CoA.

43
Q

Which statement is false regarding the catabolic oxidation of one molecule of palmitate (16:0)?

A

Eight molecules of H2O are required.

44
Q

Which statement about facilitated diffusion across a membrane is true?
A) It is impeded by the solubility of the transported solute in the non polar interior of the lipid bilayer.
B) It is responsible for the transport of gases such as O2, N2, and CH4 across biological membranes.
C) A specific membrane protein lowers the activation energy for movement of the solute through the membrane.
D) It can increase the transmembrane concentration gradient of the diffusing solute.
E) The rate is not saturable by the transported substrate.

A

C) A specific membrane protein lowers the activation energy for movement of the solute through the membrane.

45
Q

Which enzyme catalyzes the breakdown of triacylglycerols in human adipocytes?

A

Lipase

46
Q

The ultimate electron acceptor in the fermentation of glucose to ethanol is:

A

Acetaldehyde.

47
Q

Which statement is false concerning Complex III and the Q cycle?
A) Overall, in each cycle one cytochrome c is reduced for every QH2 oxidized (net).
B) Two protons from the matrix side are used to generate QH2 from the semiquinone radical
C) Both Q and QH2 are substrates for complex III
D) This protein contains both iron-sulfur clusters and heme as prosthetic groups.
E) Four protons are released on the p side of the membrane for every two electrons transferred to cytochrome c.

A

A) Overall, in each cycle one cytochrome c is reduced for every QH2 oxidized (net).

48
Q 
A prosthetic group of a protein is a nonprotein structure that is \_\_\_\_\_ the protein.
A) transiently bound to
B) permanently associated with
C) a ligand of
D) a part of the secondary structure of
E) a substrate of
A

B) permanently associated with

Biochemistry (6 decks)

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