Exam #3 Practice Questions Flashcards

1
Q

Which of the following amino acids would NOT provide a nucleophilic center for covalent catalysis?

Cysteine
Serine
Alanine
Lysine
Glutamic Acid
A

Alanine

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2
Q

In the chymotrypsin reaction mechanism, ___ is involved in covalent catalysis.

A. Asp 102
B. Ser 195
C. His 57
D. His 102
E. Asp 195
A

Ser 195

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3
Q

In the catalytic triad common to many serine proteases, ___ increases the basicity of ___, thus allowing deprotonation of ___ to serve as a nucleophile.

A. Ser-His-Asp
B. Ser-His-His
C. His-Ser-Asp
D. Asp-His-Ser
E. Cys-His-Ser
A

D. Asp-His-Ser

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4
Q

Which of the following is false regarding serine proteases?

A) they employ metal ion catalysis
B) They contain a catalytic triad of His, Ser, and Asp residues
C) They cleave simple organic ester bonds near larger residues
D) They employ general acid-base catalysis

A

A) they employ metal ion catalysis

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5
Q

An enzyme that has the maximum activity at pH 4 may indicate the involve of ___ amino aid in acid-base catalysis.

A) Lysine
B) Cysteine
C) Arginine
D) Histidine
E) Glutamic Acid
A

E) Glutamic Acid

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6
Q

All are characteristics of allosteric enzymes except:

A) They obey Michaelis-Menton kinetics
B) Effectors may show stimulatory or inhibitory activity.
C) They have multiple subunits
D) The regulatory effect by altering conformation and interaction of subunits
E) Binding one subunit impacts the binding of substrate to other subunits

A

A) They obey Michaelis-Menton kinetics

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7
Q

Proinsulin is converted to insulin by:

A) Proteolytic excision of a specific peptide
B) Allosteric binding of glucose
C) None of the above
D) Removal of phosphate by converter enzymes
E) Phosphorylation to the active form

A

A) Proteolytic excision of a specific peptide

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8
Q

Heme is a porphyrin prosthetic group that coordinates __ at four positions.

A) Fe 1+
B) Fe
C) Fe 2+
D) Fe 3+

A

C) Fe 2+

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9
Q

Which of the following is generally true for catabolism, but not anabolism?

A) A net production of energy results from degradation of large molecules
B) Pathways are compartmentalized within eukaryotic cells
C) All reactions are reversible
D) Energy may be required some, but not all intermediate steps

A

A) A net production of energy results from degradation of large molecules

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10
Q

All are coenzymes with an adenine nucleotide portion except:

A) NADH
B) FADH2
C) Coenzyme A
D) ATP
E) FMNH2
A

E) FMNH2

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11
Q

What is a characteristic difference between FAD and NAD+?

A

NAD+ transfers two electrons while FAD can transfer one or two.

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12
Q

What does not contribute to a large negative delta G of ATP?

A) Phosphate hydrolysis
B) All of the above contribute
C) Smaller solvation energy
D) Resonance stabilization
E) Electrostatic repulsion
A

B) All of the above contribute

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13
Q

__ can bypass the regulatory step at 3-FTK to enter glycolysis which may be a contributing factor to obesity.

A

Fructose

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14
Q

All are allosteric regulators of phosphofructokinase-1 except:

A) Citrate by inhibition
B) Beta-D-fructose-2,6-bisphosphate by stimulation
C) glucose-6-phosphate by inhibition
D) ATP by inhibition
E) AMP by stimulation
A

C) glucose-6-phosphate by inhibition

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15
Q

All are true for 2,3-bisphosphoglycerate (2,3-BPG) except:

A) A kinase converts 2,3-BPG to 3-phosphoglycerate
B) 2,3-BPG is involved in unloading oxygen from hemoglobin
C) 2,3-BPG is synthesized from 1,2-BPG
D) Erythrocytes typically have high levels of 2,3-BPG
E) Bisphosphoglycerate mutase is an isomerase

A

A) A kinase converts 2,3-BPG to 3-phosphoglycerate

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16
Q

Which step in metabolism produces a 3-C aldose and a 3-C ketose from a 6-C sugar?

A) Fructose bisphosphate aldolase
B) Pyruvate dehydrogenase
C) Triose phosphate isomerase
D) Pyruvate kinase

A

A) Fructose bisphosphate aldolase

17
Q

In alcohol fermentation from glucose, the two oxidation-reduction reactions are catalyzed by:

A) Glyceraldehyde-3-phosphate dehydrogenase and lactate dehydrogenase
B) Alcohol dehydrogenase and pyruvate decarboxylase
C) Glyceraldehyde-3-phosphate dehydrogenase and alcohol dehydrogenase
D) Lactate dehydrogenase and pyruvate decarboxylase

A

C) Glyceraldehyde-3-phosphate dehydrogenase and alcohol dehydrogenase

18
Q

Pyruvate dehydrogenase is a multi-enzyme complex homologous to ___.

A

Alpha ketoglutarate dehydrogenase

19
Q

Order the coenzymes according to their involvement in the pyruvate dehydrogenase complex:

A) NAD+
B) CoA-SH
C) TPP
D) Lipoate (lipoamide)
E) [FAD]
A

C, D, B, E, A

20
Q

Allosteric inhibitors of isocitrate dehydrogenase include __ and __, wheras __ acts as an allosteric activator, __ the Km for isocitrate.

A) NADH; ATP; ADP; increasing
B) NADH; ATP; AMP; lowering
C) ATP; NADH; ADP; lowering
D) NADH; NADPH; AMP; lowering
E) ATP; ADP; AMP; lowering
A

C) ATP; NADH; ADP; lowering

21
Q

List the names of 5 enzymes that are regulated in glycolysis and the TCA cycle:

A
22
Q

All are true statements for the glyoxylate pathway except:

A) bypasses the oxidative-decarboxylation steps of the TCA cycle.
B) Although glyoxysomes are found in germinating seeds, they disappear after a plant begins photosynthesis
C) The glyoxylate pathway enzymes are found in glyoxysomes
D) Isocitrate is routed through isocitrate lyase and malate synthase
E) Glyoxysomes contain all of the enzymes for the glyoxylate cycle

A

E) Glyoxysomes contain all of the enzymes for the glyoxylate cycle