Download Chemistry 326 Name_____________________ Fall 2009 Check

Chemistry 326
Fall 2009
Name_____________________
Check Section:
Tuesday ______
Wednesday_____
Thursday ______
Exam 3
If I cannot read your writing I will not grade the answer and it will be assigned “0”
points.
1. Multiple Choice (choose the best answer) (2pts each)
1. Which of these enzymes is a control point, regulated by the cell’s energy
supply?
a. glycogen synthase
d. all of these are control points
b. phosphofructokinase-1
e. none of these is a control point
c. pyruvate kinase
2. 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. phosphoglucoiosmerase
d.
3-phosphoglycerate kinase
b. phosphofructokinase-1
e.
aldolase
c. enolase
3. Which of the following statements about gluconeogenesis is not true?
a. For starting materials, it can use carbon skeletons derived from certain amino acids.
b. It required metabolic energy (ATP or GTP).
c. It is one of the ways that mammals maintain normal blood glucose levels between meals.
d. It employs the enzyme glucose-6-phosphatase
e. It consists entirely of the reaction of glycolysis, operating in the reverse direction.
4. A person who cannot synthesize liver fructose-1,6-bisphosphatase would
probably experience
a. failure to synthesize fats when the diet contained excess carbohydrate
b. inability to metabolize fructose
c. inability to convert fructose-1,6-bisphosphate into triose phosphates
d. inability to resynthesize glucose from lactate produced during exercise
e. none of the above
5. The conversion of one mole of fructose-1,6-biphosphate to two moles of
pyruvate by the glycolytic pathway results in a net formation of
a. one mole of NAD+ and two moles of ATP
b. one mole of NADH and one mole of ATP
c. two moles of NADH and two moles of ATP
d. two moles of NADH and four moles of ATP
e. two moles of NAD+ and four moles of ATP
6. The steps of glycolysis between glyceraldehyde-3-phosphate and 3phosphoglycerate involve all of the following except:
a. ATP synthesis
d. the formation of 1,3bisphosphoglycerate
b. utilization of Pi
e. catalysis of phosphoglycerate kinase
c. oxidation of NADH to NAD+
7. When a muscle is stimulated to contract aerobically, less lactic acid is formed
than when it contracts anaerobically because:
a. aerobic conditions prevent the activation of phosphorylase and make less
substrate available for glycolysis
b. under aerobic conditions most of the pyruvate generated as a result of
glycolysis is oxidized by the citric acid cycle rather than reduced to lactate
c. the lactic acid generated is rapidly incorporated into lipids under aerobic conditions
d. under aerobic conditions in muscle, the major energy-yielding pathway is
the pentose phosphate pathway, which does not produce lactate
e. muscle is metabolically less active under aerobic and anaerobic conditions
8. Glucokinase
a. is found in all mammalian tissues
b. converts glucose-6-phosphate to fructose-6-phosphate
c. is a hexokinase isozyme found in the liver
d. acts in the conversion of liver glycogen to glucose-1-phosphate
___ 9.
During strenuous exercise, the NADH formed in the glyceraldehyde-3phosphate 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:
a. oxaloacetate → malate
b. pyruvate → lactate
c. dihydroxyacetone phosphate → glycerol-3-phosphate
d. isocitrate → α-ketoglutarate
e. glucose-6-phosphate → fructose-6-phosphate
10. The conversion of one mole of glucose-6-phosphate to two moles of lactate in
glycolysis is accompanied by a net gain of
a. three moles of ATP
d. one mole of NADH
b. two moles of ATP
e. none of these
c. one mole of ATP
11. Which of these cofactors participates directly in both oxidation-reduction
reactions in fermentation of glucose to lactate?
a. FAD/FADH2
d. ATP
b. NAD+/NADH
e. ADP
c. glyderaldehyde-3-phosphate
12. Glycogen is converted to monosaccharide units by:
a. glycogenase
c. glycogen synthase
b. glycogen phosphorylase
d. glucokinase
13. The enzyme glycogen phosphorylase
a. uses glucose as a substrate
b.
c.
d.
e.
__ 14.
uses glucose-6-phosphate as a substrate
catalyzes a hydrolytic cleavage of α(1→4) bonds
catalyzes a cleavage of β(1→4) bonds
is a substrate for a kinase
Which of the following is true of glycogen synthase?
a. It catalyzes addition of glucose residues to the nonreducing end of a glycogen chain
through (α1→4) bonds.
b. The conversion of an active to an inactive form of the enzyme is
controlled
by the concentration of cAMP.
c. Activation of the enzyme involves a phosphorylation.
d. The enzyme has measurable activity only in liver.
15. Which of the following is true of glycogen synthesis and breakdown?
a. Synthesis is catalyzed by the same enzyme that catalyzes breakdown.
b. The immediate product of glycogen breakdown is free glucose.
c. Phosphorylation activates the enzyme responsible for breakdown, and inactivates
the synthetic enzyme
d. Under normal circumstances glycogen synthesis and glycogen breakdown occur
simultaneously at high rates.
e. The glycogen molecule “grows” at its reducing end.
16. Glycogenin
a. is the gene that encodes glycogen synthase
b. is the primer on which new glycogen chains are initiated
c. is the enzyme responsible for forming branches in glycogen
d. regulates the synthesis of glycogen
e. catalyzes the conversion of starch into glycogen
17. Glucagon (in liver) and epinephrine (in muscle)
a. activate glycogen phosphorylase and inactivate glycogen synthase
b. inhibit glycogen synthesis and activate glycogenolysis
c. act by raising the concentration of cyclic AMP (cAMP)
d. oppose the effects of insulin on these tissues
e. do all of the above
___ 18. How many moles of ATP are produced from fermentation of maltose?
a. 4 ATPs
d. 6-8 ATPs
b. 2 ATPs
e. None of the above
c. 36-38 ATPs
____ 19.
Glycogen synthase and phosphorylase kinase are:
a. Are modified by the same enzymes
b. Are not subjected to allosteric control
c. Are not subjected to covalent modification
d. None of the above
____ 20.
____ 21.
The compound UDPG plays a role in
a. Glycogen breakdown
b. Glycogen synthesis
c. EMP
d. GNG
e. None of the above
a.
b.
c.
d.
e.
Substrate-level phosphorylation occurs in EMP in the reaction catalyzed by
Hexokinase
Glucokinase
PFK-I
3-phosphoglycerate kinase
All of the above
____22.
In the Cori Cycle
a. Lactose is transported from muscle to liver by the blood
b. Lactate is transported from the liver to the kidneys by the blood
c. EMP takes place in the muscle and GNG in the liver
d. EMP takes place in the liver and GNG in the muscle
___ 23.
In the coordinated control of PFK-I and fructose 2,6-bisphosphatase
a. Citrate inhibits PFK-I and stimulates fructose 2,6-bisphosphatase
b. Fructose 2,6-bisphosphate inhibits PFK-I and stimulates fructose 2,6bisphosphatase
c. AMP inhibits PFK-I and stimulates fructose 2,6-bisphosphatase
d. All of the above
e. None of the of the above
____24.
Which of the following is the enzyme incorrectly paired with its allosteric effector?
a. Hexokinase: G-6-P
b. PFK-I: glucose-6-phosphate
c. PFK-I:ADP
d. Pyruvate kinase:Alanine
____25.
The steps of EMP between Glyceraldehyde-3-phosphate and 3-phosphoglycerate involve all
of the following except:
a. ATP synthesis
b. The utilization of orthophosphate
c. The oxidation of NADH
d. The formation of 1,3-bispohosphoglycerate
e. Catalyzed by phosphoglycerate kinase
2. Alginic acids, isolated from seaweed, is used as a thickening agent for ice
cream and other foods. It is a polymer of D-mannuronic acid with β(1,4)
glycosidic (acetal) linkages.(9pts) Use pyranose structures.
a. Draw the structure of D-mannuronic. (No partial credit)
b. Draw the structure of alginic acid You need only draw two residues of the
polymer. (No partial credit)
c. Draw and name the C2 epimer of mannuronic acid. (No partial credit).
3. The active form of glycogen phosphorylase is allosterically inhibited by glucose and
caffeine. How does this action of caffeine relate to the more familiar action of stimulation
people usually experience from drinking coffee and other beverages that contain
caffeine? (5pts)
4. Consider glycolysis and answer the following questions. (10pts)
a. Which steps involve SLP. No structure needed.
b. Which step is redox. No structures needed.
c. Which step is dehydration. No structures needed.
Choose ONE reaction from your answers above and give the complete reaction with the
structure and the name of the substrate and the product, name the enzyme and any CoE if
used in the reaction.
5. In many tissues, one of the earliest responses to cellular injury is a rapid increase in the
enzyme levels of HMP. Ten days after an injury heart tissue has levels of the enzymes
found in the Phase 1 of HMP. They are usually 20-30 times greater than normal. In
contrast the normal enzyme levels of EMP are only ~10% the normal level.
Explain.(5pts)
6. Place the following in the order in which they occur: NO PARTIAL CREDIT:(5pts)
_____a. Phosphorylation of synthase and phosphorylase kinase
_____b. Activation of Protein kinase
_____c. Phosphorylation of phosphorylase
_____d. Hormone binding to cell receptor
_____e. Formation of cAMP
For questions 7a-b:
7. Glucagon promotes glycogen breakdown: it’s the “We’re hungry” hormone. Heart
muscle cells do not respond to glucagon, but epinephrine similarly stimulates glycogen
breakdown in these cells. The effects of glucagon or epinephrine (“Fight or flight”) are
mediated through the protein kinase, which phosphorylates the bifunctional
phosphofructokinase-2/fructose-bisphosphatase-2 (PFK-2/FBPase-2) enzyme.
a. (10 pts) In the liver, which activity of PFK-2/FBPtase-2 is increased and which
activity is decreased upon phosphorylation of the enzyme?
How does this eventually lead to the appropriate response to a lack of blood
glucose?
b. (6 pts) Heart muscle also responds to elevated cAMP by phosphorylation of PFK2/FBPase-2, but the effect on which activity goes up and which goes down is opposite
from the liver. How is this possible? A two word answer would do.