Test bank for Biochemistry | Chapter 16, Chapter 13 Principles of Bioenergetics,
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CBSE Biochem
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CBSE Biochem
Test bank for Biochemistry
12, BC II HW1 E1, Chapter 16, Chapter 13 Principles of Bioenergetics, Biochem Test 1, biochem exam 1, Ch 13 Kinetics Bioenergetics, Bioenergetics, Chapter 12, Ch 12 Biosignaling, Questions 12
12, BC II HW1 E1, Chapter 16, Chapter 13 Principles of Bioenergetics, Bio...
Test bank for Biochemistry
12, BC II HW1 E1, Chapter 16, Chapter 13 Principles of Bioenergetics,
Biochem Test 1, biochem exam 1, Ch 13 Kinetics Bioenergetics, Bioenergetics,
Chapter 12, Ch 12 Biosignaling, Questions 12
Which of the following is true of the binding energy derived from enzyme-substrate interactions?
A. It cannot provide enough energy to explain the large rate accelerations brought about by
enzymes.
B. Most of it is used up simply binding the substrate to the enzyme.
C. Most of it is derived from covalent bonds between enzyme and substrate.
D. It is sometimes used to hold two substrates in the optimal orientation for reaction.
E. It is the result of covalent bonds formed between enzyme and substrate. ** answer**D. It is
sometimes used to hold two substrates in the optimal orientation for reaction.
Of the following mechanisms, which would not contribute to enzyme catalysis?
A. the use of binding interactions to distort bond angles or bond lengths of a substrate to better
approximate those of a transition state intermediate
B. the greater affinity of the active site for binding the substrate relative to the affinity for
binding the transition state intermediate
C. hydrogen bonding of basic amino acid R groups with a substrate
D. the formation of a covalent intermediate ** answer**B. the greater affinity of the active site
for binding the substrate relative to the affinity for binding the transition state intermediate
Phenyl-methane-sulfonyl-fluoride (PMSF) inactivates serine proteases by binding covalently to
the catalytic serine residue at the active site; this enzyme-inhibitor bond is not cleaved by the
enzyme. This is an example of what kind of inhibition? ** answer**irreversible
Both water and glucose share an —OH that can serve as a substrate for a reaction with the
terminal phosphate of ATP catalyzed by hexokinase. Glucose, however, is about a million times
more reactive as a substrate than water. The best explanation is that: ** answer**the larger
,glucose binds better to the enzyme; it induces a conformational change in hexokinase that brings
active-site amino acids into position for catalysis.
In kinetic analyses of chemical reactions ** answer**comparing reactions is simplified by using
initial velocities (v0).
When comparing enzymes the KM ** answer**is greater for enzymes with lower affinities for a
substrate.
The turnover number (kcat) of an enzyme ** answer**is a function of VMAX and the total [E].
The reasons some cancer patient's cancers do not respond to chemotherapy include
A. decreased DNA repair activity.
B. increased cellular export.
C. increased tumor blood supply.
D. inactivation of the P450 detoxifying system.
E.increased programmed cell death signaling. ** answer**B. increased cellular export.
ABC transporters normally function
A. all three of these functions.
B. to protect the genomes of normal stem cells in our bodies.
C. to keep toxins in the mother's blood from affecting a developing fetus.
D. to keep toxins from crossing the blood-brain barrier. ** answer**A. all three of these
functions.
Multidrug resistance proteins ** answer**can interfere with treating brain disorders by keeping
drugs from entering the brain from our blood.
The lipid bilayer of biological membranes ** answer**is self sealing in an aqueous environment
Membrane lipids are classified ** answer**first by backbone and second by head groups
,Amphipathic alpha-helical structures can form a ** answer**hydrophilic pore within a lipid
bilayer
Amphipathic ** answer**a molecule with both hydrophobic and hydrophilic groups. i.e.
detergent
A hydropathy plot indicates ** answer**a stretch of amino acids forming a single-pass
transmembrane domain
Sodium (Na+) transport across a membrane ** answer**uses ~30% of the ATP hydrolyzed in
mammalian cells.
Aerobic glycolysis or the Warburg Effect ** answer**can be visualized through PET scans
Adenosine 5'-triphosphate (ATP) ** answer**can be used as a cosubstrate by enzymes to drive
unfavorable reactions
Biological oxidation-reduction reactions always involve ** answer**a transfer of electron(s)
The coenzyme NAD+ ** answer**carries only one hydride anion (1 H + 2 e-s)
The conversion of 1 mol of fructose 1,6-bisphosphate to 2 mol of pyruvate by the glycolytic
pathway results in a net formation of ** answer**2 mol of NADH and 4 mol of ATP
When a mixture of glucose 6-phosphate and fructose 6-phosphate is incubated with the enzyme
phosphohexose isomerase, the final mixture contains twice as much glucose 6-phosphate as
fructose 6-phosphate. Which one of the following statements is most nearly correct, when
applied to the reaction below (R = 8.315 J/mol•K and T = 298 K)? Glucose 6-phosphate ↔
fructose 6-phosphate ** answer**ΔG'° is +1.7 kJ/mol.
, The steps of glycolysis between glyceraldehyde 3-phosphate and 3-phosphoglycerate involve all
of the following except:
A. oxidation of NADH to NAD+.
B. utilization of Pi.
C. the formation of 1,3-bisphosphoglycerate.
D. catalysis by phosphoglycerate kinase.
E. ATP synthesis. ** answer**oxidation of NADH to NAD+.
All of the following enzymes involved in the flow of carbon from glucose to lactate (glycolysis)
are also involved in the reversal of this flow (gluconeogenesis) except
A. aldolase.
B. 3-phosphoglycerate kinase.
C. phosphofructokinase-1.
D. phosphoglucoisomerase.
E. enolase. ** answer**C. phosphofructokinase-1.
A reaction at equilibrium in a metabolic pathway is ** answer**a rapid and reversible step
In glycolysis, fructose 1,6-bisphosphate is converted to two products with a standard free-energy
change (∆G'°) of 23.8 kJ/mol. Under what conditions (encountered in a normal cell) will the
free-energy change (∆G) be negative, enabling the reaction to proceed to the right? **
answer**When there is a high concentration of fructose 1,6-bisphosphate relative to the
concentration of products
During strenuous exercise, the NADH formed in the glyceraldehyde 3-phosphate dehydrogenase
reaction in skeletal muscle must be reoxidized to NAD+ if glycolysis is to continue. The most
important reaction involved in the reoxidation of NADH is: ** answer**pyruvate → lactate
The anaerobic conversion of 1 mol of glucose to 2 mol of lactate by fermentation is accompanied
by a net gain of: ** answer**2 mol of ATP
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