Download Biochemistry 423 Final Examination

Biochemistry 423
Final Examination
NAME: ________________________________________________________________
1
Circle the single BEST answer (3 points each)
1.
At equilibrium the free energy of a reaction ∆G
A.
B.
C.
D.
2.
The presence of a catalyst,
A.
B.
C.
D.
3.
lysine
histidine
glutamate
arginine
aspartate
A tripeptide was treated with trypsin and produced a single amino acid and a dipeptide
that had a UV absorbance. The same tripeptide, when exposed to chymotrypsin,
produced a dipeptide and a single amino acid that had a UV absorbance. If hydrolysis of
the tripeptide produced Ala, Lys, and Tyr, what was the sequence of the amino acids in
the tripeptide?
A.
B.
C.
D.
E.
5.
decreases ∆G
does not affect ∆G
increases ∆G
increases ∆G0’
Which amino acid has a side chain group with a pKa closest to physiological pH?
A.
B.
C.
D.
E.
4.
depends only on the temperature
is positive
is 0
is negative
Ala-Lys-Tyr
Ala-Tyr-Lys
Tyr-Ala-Lys
Tyr-Lys-Ala
Lys-Ala-Tyr
Which of the following statements is true?
A.
B.
C.
D.
E.
all fibrous proteins have quaternary structure
all globular proteins have quaternary structure
all proteins have quaternary structure
the interactions between the eight helical regions is partially responsible for the
quaternary structure of myoglobin
only proteins with more than one subunit have quaternary structure
2
6.
In a globular protein, a leucine residue would most likely be found
A.
B.
C.
D.
E.
7.
Which of the following peptides would most likely be found in the interior of the cell
membrane?
A.
B.
C.
D.
E.
8.
C.
D.
E.
each of the four oxygen molecules binds with equal facility
the binding of the first oxygen molecule enhances the binding of the other three
oxygen molecules
the binding of the first oxygen molecule makes the binding of the other three
oxygen molecules more difficult
the binding of the first oxygen molecule has no effect on the binding of the
remaining three oxygen molecules.
each successive oxygen bound makes the remaining sites less likely to bind
oxygen
Under which of the following conditions will hemoglobin bind less oxygen?
A.
B.
C.
D.
E.
10.
Asp-Glu-Gln-Asp
Lys-Arg-Val-Lys
His-Glu-Ser-Asn
Met-Val-Ile-Phe
Ser-Met-Asp-Gln
Which of the following statements describes the oxygen-binding curve of hemoglobin?
A.
B.
9.
participating in hydrogen bonds involving R-groups
on the outside surface
on the interior
both on the interior and outside surface
leucine residues are rarely found in globular proteins
the pH increases from 7.0 to 7.2
the oxygen pressure increases from 500 mm to 1000 mm
the concentration of carbon dioxide increases
the bis-phosphoglycerate is removed
none of the above
Which of the following techniques cannot give information about the size of a protein?
A.
B.
C.
D.
E.
amino acid composition
SDS-electrophoresis
ion-exchange chromatography
gel-exclusion chromatography
none of the above
3
11.
Which of the following affects the rate of a reaction?
A.
B.
C.
D.
E.
12.
Which of the following is NOT true concerning competitive inhibition of an enzyme
catalyzed reaction?
A.
B.
C.
D.
E.
13.
Km increases
Km decreases
Vmax increases
Vmax decreases
Vmax and Km decreases
The Km is:
A.
B.
C.
D.
E.
15.
the inhibition cannot be overcome by increasing the concentration of the reactant
the competitive inhibitor resembles the substrate
the competitive inhibitor binds to the same site as does the substrate
the competitive inhibitor does not allow the substrate to bind to the enzyme.
The inhibition can be overcome by increasing the concentration of the reactant
Which of the following statements is true about non-competitive inhibition?
A.
B.
C.
D.
E.
14.
the number of reactant collisions per unit time
the energy of each collision
the orientation of the particles in each collision
the temperature
all of the above
the time for half of the substrate to be converted to product.
The time for all of the substrate to be converted to product.
The [S] that gives half of the maximum reaction rate
The [S] that gives the maximum reaction rate
The [P] that is produced when the enzyme is saturated with the substrate.
Allosteric enzymes generally exhibit
A.
B.
C.
D.
linear kinetics
hyperbolic kinetics
classical Michaelis-Menten kinetics
sigmoidal kinetics
4
16.
A zymogen is:
A.
B.
C.
D.
E.
17.
an inactive precursor
an active precursor
an inactive product
an active product
none of the above
What coenzyme, or coenzyme pair, would you expect to be associated with the
following conversion?
OOC-CH2-CH2-COO
A.
B.
C.
D.
E.
18.
FAD / FADH2
NAD+ / NADH
pyridoxal phosphate (B6)
biotin
B12
What coenzyme, or coenzyme pair, would you expect to be associated with the
following conversion?
O
O C C O
CH2
CH2
C O
O
A.
B.
C.
D.
E.
19.
OOC-CH=CH-COO
+
O
H3N CH C O
CH3
O
O C C O
CH3
FAD / FADH2
NAD+ / NADH
pyridoxal phosphate (B6)
biotin
B12
One-carbon transfers are mediated by
A.
B.
C.
D.
E.
THF deerivatives
coenzyme A
lipoic acid
thiamine pyrophosphate
pyridoxal phosphate
5
O
H3N CH C O
CH2
+
CH2
C O
O
20.
Which of the following conversions is catalyzed by the enzyme 3-phosphoglycerate
kinase?
A.
B.
C.
D.
21.
Which of the following, as a starting material for glycolysis, will result in the highest net
yield of ATP?
A.
B.
C.
D.
22.
phosphofructokinase
fructose bisphosphate phosphatase
pyruvate kinase
hexokinase
glyceraldehyde 3-phosphate dehydrogenase
Two carbons from a molecule of pyruvate enter the citric acid cycle by the actions of
which two enzymes?
A.
B.
C.
D.
24.
glucose
fructose
glycogen
they would all produce equivalent net amounts of ATP
Which of the following enzymes catalyzes reactions in both glycolysis and
gluconeogenesis?
A.
B.
C.
D.
E.
23.
glycerate 2-phosphate to phosphoenolpyruvate
glycerate 3-phosphate to glycerate 2-phosphate
glycerate 1,3-bisphosphate to glycerate 3-phosphate
glyceraldehyde 3-phosphate to dihydroxyacetone posphate
pyruvate kinase and enolase
pyruvate carboxylase and malate dehydrogenase
pyruvate dehydrogenase and citrate synthetase
pyruvate carboxylase and pyruvate dehydrogenase.
All three carbons of pyruvate can enter the citric acid cycle by way of which of the
following enzymes?
A.
B.
C.
D.
E.
pyruvate dehydrogenase
pyruvate decarboxylase
pyruvate carboxylase
pyruvate kinase
citrate synthetase
6
25.
Which of the following is NOT a coenzyme for the pyruvate dehydrogenase complex?
A.
B.
C.
D.
E.
26.
Which oxidative phosphorylation complex is directly responsible for ATP production?
A.
B.
C.
D.
E.
27.
palmitoyl-CoA
acetyl-CoA
acetoacetyl-CoA
malonyl-CoA
linoleoyl-CoA
The complete β-oxidation of palmitoyl-CoA to CO2 and water requires how many cycles
through the pathway?
A.
B.
C.
D.
E.
29.
complex IV
iron-sulfur complex
F0 complex
F1 complex
F0/F1 complex
Which of the following molecules is the direct product of an enzyme that uses biotin as a
coenzyme?
A.
B.
C.
D.
E.
28.
CoASH
thiamine pyrophosphate
ATP
FAD
lipoic acid
seven
eight
nine
ten
sixteen
When in excess, amino acids may be degraded. The first step in degradation of most
amino acids is:
A.
B.
C.
D.
E.
decarboxylation
oxidation of the side chain
elimination of functional groups such as hydroxyl and sulfhydryl groups
transamination
racemization
7
30.
Ammonia is transported from skeletal muscle to the liver as:
A.
B.
C.
D.
E.
31.
The accumulation of an oxygen debt during strenuous physical exercise may be
accompanied by:
A.
B.
C.
D.
E.
32.
production of NADPH
production of ribose-5-phosphate
remodeling of dietary carbon atoms into 2,3-bisphosphoglycerate
synthesis of ATP
reduction of H2O2 to two moles of H2O
Under conditions of anaerobic glycolysis, the NAD+ required by glyceraldehyde 3phosphate dehydrogenase is supplied by a reaction catalyzed by
A.
B.
C.
D.
E.
34.
an increase in NAD+ in muscle
an increase in lactate in blood
a decrease in pyruvate in blood
an increase in citrate in muscle
an increase in ATP in muscle
Which of the following represents the primary function of the pentose phosphate
pathway in erythrocytes?
A.
B.
C.
D.
E.
33.
ammonium salts
glutamine and alanine
glutamate and aspartate
urea
uric acid
pyruvate dehydrogenase
α-ketoglutarate dehydrogenase
glycerol 3-phosphate dehydrogenase
malate dehydrogenase
lactate dehydrogenase
All of the following are essential amino acids except
A. phenylalanine
B. valine
C. cysteine
D. isoleucine
E. leucine
8
35.
The sequence of a DNA strand is 5'---pApGpCpG--3'. The sequence of a
complementary segment of DNA is:
A. 5'--pTpCpGpC--3'
B. 5'--pCpGpCpU--3'
C. 5'--pCpApTpA--3'
D. 5'--pCpGpCpT--3'
E. 5'--pUpCpGpC--3'
36.
A codon is a three-nucleotide sequence of
A.
B.
C.
D.
E.
37.
Molecules involved in purine nucleotide synthesis include all of the following
EXCEPT:
A.
B.
C.
D.
E.
38.
Phosphoribosyl pyrophosphate (PRPP)
Aspartate
S-adenosylmethionine (SAM)
N10-formyl THF
CO2
One-carbon carriers in biosynthetic processes include all of the following EXCEPT:
A.
B.
C.
D.
39.
tRNA
DNA, read in the 5' to 3' direction
mRNA, read in the 5' to 3' direction
rRNA
mRNA, read in the 3' to 5' direction
SAM
Thymine
THF
Biotin
All of the following are glucogenic amino acids EXCEPT:
A.
B.
C.
D.
E.
Glycine
Leucine
Alanine
Aspartate
Serine
9
40.
Which of the following provides the energy to move the ribosome along the mRNA?
A.
B.
C.
D.
E.
41.
ATP
dATP
GTP
UTP
dUTP
Which of the following statements is false?
A.
B.
C.
D.
E.
There is at least one tRNA for each of the amino acids.
The attachment site for the amino acid is at the 3' end of the tRNA molecule.
Each tRNA accepts a specific amino acid.
A, C, G and U are the only bases in tRNA.
There is a specific tRNA for initiation of protein synthesis.
Select ALL Correct Responses (3 points each)
42.
Fatty acid synthesis requires which of the following cofactors? (CIRCLE ALL
CORRECT ANSWERS)
A.
B.
C.
D.
E.
carnitine
NADPH
FAD
biotin
thiamine pyrophosphate
10
Fill in the Blank
43.
Indicate where in the eukaryotic cell the following processes take place: (2 pts each)
A. Glycolysis ____________________________________________________
B. Urea Cycle ___________________________________________________
C. DNA replication _______________________________________________
D. RNA synthesis _________________________________________________
E. Fatty acid synthesis _____________________________________________
F. Protein synthesis _______________________________________________
G. Fatty acid oxidation _____________________________________________
44.
Mark each of the following statements T (true) or F (false) (2 pts each)
_____ E. coli DNA polymerases contain both polymerase and nuclease activities on the
same polypeptide chain.
_____ DNA polymerase I does not require a template.
_____ Only DNA polymerase III is capable of “editing” (i.e., has 3' to 5'-nuclease
activity).
_____ The link between nucleotides in RNA and DNA is a phosphodiester bond.
_____ A highly processive enzyme stays bound to its substrate as it catalyzes a sequence
of reactions.
_____ Thymine (rather than uracil) is found in DNA in order to ensure that chemical
damage to DNA is repaired.
_____ Prokaryotic and eukaryotic ribosomes contain the same number of rRNA
molecules.
_____ Transfer RNA (tRNA) is the largest type of RNA.
_____ RNA polymerase binds to DNA at promoter regions.
_____ In protein synthesis, four high energy bonds are hydrolyzed for each peptide bond
formed.
11
45.
Mark each of the following statements T (true) or F (false) (2 pts each)
_____ Acyl carrier protein is the principal regulated protein of fatty acid synthesis.
_____ Membranes are phospholipid monolayers containing imbedded proteins.
_____ A membrane channel accomplishes transport of a molecule or ion against a
concentration gradient.
_____ Carbon atoms in the purine base ring structure come from CO2, N5,N10formylTHF and alanine.
_____ Ribonucleotides are reduced to deoxyribonucleotides at the di- phosphorylation
level.
_____ The principal positive allosteric effectors of pyrimidine synthesis are purine
nucleotides.
_____ Phospholipids contain glycerol, two fatty acids, phosphate and an aromatic
amino acid.
_____ Triacylglycerols (TAGs) are the principal component of storage fat.
_____ DNA polymerase II of E. coli is primarily responsible for DNA repair.
_____ DNA replication is semi-conservative.
_____ DNA with high GC content has a lower melting point than DNA with high AT
content.
_____ Eukaryotic DNA is linear.
_____ Okazaki fragments are involved in the synthesis of the lagging strand of DNA
during replication.
_____ RNA polymerases require a primer.
_____ The direction of the strands in the DNA double helix is parallel.
_____ In eukaryotes, all proteins are synthesized in the compartment in which they will
function.
12
46.
Fill in the blanks. (2 pts each).
1.
In prokaryotes, a system of genes under coordinated regulation is called
________________________.
2.
An inducer binds to a _________________ protein that is the product of a
regulator gene.
3.
If the concentration of glucose in E. coli is low, the bacteria make
________________________.
4.
Proteins whose synthesis can not be induced or repressed are called
________________________.
5.
Eukaryotic DNA and histone proteins are condensed into structures called
________________________.
47.
On the last page is a genetic code table. Determine the sequence of the protein segment
that would be synthesized by transcription and translation of the following DNA
sequence: (4 points)
5' -pApTpCpCpCpGpGpApCpCpApT- 3'
3' - TpApGpGpGpCpCpTpGpGpTpAp- 5'
13
THE GENETIC CODE
First Position
5’ end
U
C
A
G
U
Phe
Phe
Leu
Leu
Leu
Leu
Leu
Leu
Ile
Ile
Ile
Met
Val
Val
Val
Val
Second Position
C
A
Ser
Tyr
Ser
Tyr
Ser
STOP
Ser
STOP
Pro
His
Pro
His
Pro
Gln
Pro
Gln
Thr
Asn
Thr
Asn
Thr
Lys
Thr
Lys
Ala
Asp
Ala
Asp
Ala
Glu
Ala
Glu
14
G
Cys
Cys
STOP
Trp
Arg
Arg
Arg
Arg
Ser
Ser
Arg
Arg
Gly
Gly
Gly
Gly
Third Position
3’ end
U
C
A
G
U
C
A
G
U
C
A
G
U
C
A
G