Part 1:-
METABOLISM
1. Which of the following statements is true regarding metabolic pathways?
a. Catabolic pathways are generally reductive while anabolic pathways are generally oxidative
b. Catabolic pathways use a wide variety of substrates to produce a small number of waste products.
c. An amphibolic pathway is extremely wasteful because it simultaneously operates as both an anabolic pathway and a catabolic pathway.
d. NAD+ is used as a reducing agent in catabolic pathways while NADPH is used as an oxidizing agent in anabolic pathways
e. None of the above
2. What is the relationship between photoautotrophs and heterotrophic cells?
a. Photoautotrophs use light energy for synthesis of organic molecules while heterotrophs metabolize organic substances for fuel and building blocks.
b. Photoautotrophs use organic compounds as a source of carbon while heterotrophs use CO2 as a source of carbon.
c. Photoautotrophs synthesize CO2 while heterotrophs synthesize O2.
d. Heterotrophs convert solar energy into chemical energy while photoautotrophs break down organic molecules.
e. There is no relationship between the two.
3. The definition of an amphibolic pathway is:
a. A pathway found in animals living in both land and water.
b. A pathway that is carried out both in water and organic solvents.
c. A pathway found on both sides of the mitochondrial membrane.
d. A pathway that is both anabolic and catabolic in nature.
e. All of the above.
4. Since both glycolysis and gluconeogenesis are spontaneous pathways, which of the following explains how this is true?
a. Glycolysis uses 10 enzyme catalyzed steps while gluconeogenesis uses 11
b. The three irreversible steps of glycolysis have alternate routes for gluconeogenesis
c. Glycolysis converts glucose to pyruvate while gluconeogenesis converts pyruvate to glucose
d. Glycolysis is oxidative while gluconeogenesis is reductive
e. Glycolysis is catabolic while gluconeogenesis is anabolic
5. All are coenzymes with an adenine nucleotide portion EXCEPT:
a. ATP.
b. NADH.
c. Coenzyme A.
d. FADH2.
e. FMNH2.
6. For the following reaction, what coenzyme is missing from the reactants?
a. FADH2
b. NAD+
c. acetyl CoA
d. NADH
e. NADPH
7. What is a characteristic difference between FAD and NAD+?
a. NAD+ is a stronger oxidizing agent than FAD.
b. Only FAD participates in oxidation-reduction reactions.
c. NAD+ binds tightly to its enzyme while FAD only binds loosely.
d. NAD+ transfers two electrons while FAD can transfer one or two.
e. NAD+ is re-oxidized easily by molecular oxygen while FAD is not.
8. All are characteristic of the conversion of glucose to lactate EXCEPT:
a. Anaerobic pathway with no net oxidation.
b. "Primed" by ATP phosphorylation.
c. Located in the cytosol.
d. Approximately 50% efficient in erythrocytes.
e. Net production of four ATP per glucose.
9. All are important reasons to phosphorylate glucose in the first step of glycolysis EXCEPT:
a. The large positive free energy is important in getting the pathway started.
b. Glucose-6-phosphate has a negative charge preventing transport out of the cell.
c. The concentration of free glucose in the cell is lowered favoring influx of glucose.
d. Phosphorylation keeps the glucose in the cell.
e. Regulatory control can be imposed only at a reaction not at equilibrium.
10. Glucokinase has a Km value of 10.0 mM, whereas hexokinase has a Km value of 0.1 mM. This is consistent with which of the following?
a. Glucokinase acts on glucose at low concentrations.
b. Glucokinase acts on glucose only at high glucose concentrations.
c. Glucokinase phosphorylates most of the glucose at low glucose levels.
d. Hexokinase acts on glucose only at high levels of glucose.
e. Hexokinase acts at about half-maximal velocity at glucose concentrations of 4-5 mM.
11. All are true for the isomerase reaction of glucose-6-phosphate to fructose-6-phosphate EXCEPT:
a. Mg2+ is required for activity.
b. It is an aldose to ketose isomerization.
c. "Moving" the carbonyl from C-1 to C-2 creates a new primary alcohol group at C-1.
d. The reaction is irreversible with a large negative ?G.
e. The enzyme belongs to the isomerase class of enzymes.
12. All are characteristics of the phosphofructokinase-1 catalyzed reaction EXCEPT:
a. Exergonic.
b. "Priming reaction".
c. "Valve" controlling the rate of glycolysis.
d. Commits the cell to metabolize glucose.
e. All are true.
13. For phosphofructokinase-1:
a. Low ATP stimulates the enzyme, but fructose-2,6-bisphosphate inhibits
b. High ATP stimulates the enzyme, and fructose-2,6-bisphosphate activates
c. High ATP stimulates the enzyme, but fructose-2,6-bisphosphate inhibits
d. Low ATP stimulates the enzyme, and fructose-2,6-bisphosphate activates
e. ATP and fructose-2,6-bisphosphate both inhibit the enzyme
14. The high free energy change for the conversion of PEP to pyruvate is due largely to the ____ conversion of the relatively unstable ____ tautomer of pyruvate to the more stable ____ form following the phosphoryl group transfer step.
a. unfavorable; enol; keto
b. unfavorable; keto; aldol
c. favorable; keto; enol
d. favorable; enol; keto
e. favorable; enol; aldol
15. In alcohol fermentation from glucose, the two oxidation-reduction reactions are catalyzed by:
a. Glyceraldehyde-3-phosphate dehydrogenase and alcohol dehydrogenase
b. Glyceraldehyde-3-phosphate dehydrogenase and pyruvate decarboxylase
c. Alcohol dehydrogenase and pyruvate decarboxylase
d. Lactate dehydrogenase and pyruvate decarboxylase
e. Glyceraldehyde-3-phosphate dehydrogenase and lactate dehydrogenase
16. All are correct statements about the reaction catalyzed by citrate synthase EXCEPT:
a. Citrate synthase is allosterically activated by ATP.
b. The complete chemical equation is: Oxaloacetate + acetyl-CoA + H2O <-->citrate + CoA
c. Citryl-CoA is formed as an intermediate.
d. The mechanism involves attack of the carbanion of acetyl-CoA on the carbonyl carbon of oxaloacetate.
e. The enzyme uses general base catalysis to generate the reactive species.
17. The following statements are correct about the reaction catalyzed by the pyruvate dehydrogenase complex EXCEPT:
a. It is the link between glycolysis and the TCA cycle
b. The activity of the complex is regulated by the phosphorylation of EPDH.
c. NAD+ is the direct oxidant of reduced lipoamide.
d. An FAD is covalently linked to the EDLD, the lipoamide dehydrogenase component.
e. Although EPDH is called "pyruvate dehydrogenase" it is not a dehydrogenase.
18. ____ catalyzes citrate isomerization to isocitrate by abstracting ____ from citrate to yield the enzyme-bound intermediate ____, followed by ____ to produce isocitrate.
a. Citrate isomerase; CO2; trans-aconitate; carboxylation
b. Citrate isomerase; water; trans-aconitate; rehydration
c. Aconitase; water; cis-aconitate; rehydration
d. Aconitase; CO2; cis-aconitate; carboxylation
e. None are true
19. Fumarase catalyzes a reaction for which each of the following is true EXCEPT:
a. Fumarate is hydrated
b. The reaction is stereospecific for a trans product
c. The reaction involved is similar to that carried out by aconitase
d. L-malate is the produced
e. All are true
20. Gluconeogenesis is the synthesis of:
a. Glucose from non-carbohydrate precursors.
b. Glycogen from glucose.
c. Pyruvate from glucose.
d. Fatty acids from glucose.
e. Glucose from fatty acids.
21. The pentose phosphate pathway is an important source of ____, and for ____, an essential precursor for ATP, NAD+ , FAD, CoA, DNA and RNA.
a. ATP; NADH
b. NADH; NADPH
c. NADPH; ribose-5-phosphate
d. ribose-5-phosphate; ATP
e. all are true
22. In the gluconeogenic pathway, the three regulated reactions of glycolysis catalyzed by ____, ____ and ____ are replaced by alternative reactions.
a. glucokinase; PFK-1; pyruvate kinase
b. phosphoglucoisomerase; PFK-1; pyruvate kinase
c. PFK-1; triose phosphate isomerase; pyruvate kinase
d. glucokinase; PFK-1; glyceraldehyde-3-phosphate dehydrogenase
e. glucokinase; PFK-1; pyruvate carboxylase
23. If levels of ____ and/or ____ are low, pyruvate is directed primarily into ____; but if they are high, pyruvate is converted into ____ for gluconeogenesis.
a. NADH; ATP; glycolysis; Oxaloacetate
b. ATP; NADPH; glycolysis; acetyl CoA
c. ATP; acetyl CoA; TCA cycle; Oxaloacetate
d. NAD+; acetyl CoA; TCA cycle; acetyl CoA
e. ATP; acetyl CoA; glycolysis; malate
24. Glucose-6-phosphatase is located in the ____ and produces ____ in vesicles that diffuse to the ____ releasing their contents into the blood stream.
a. mitochondria; lactate; cytosol
b. cytosol; glucose; plasma membrane
c. endoplasmic reticulum; glucose-6-phosphate; cytosol
d. endoplasmic reticulum; glucose; plasma membrane
e. cytosol; glucose-6-phosphate; endoplasmic reticulum
25. All are true for α-amylase EXCEPT:
a. catalyzes hydrolysis of α (1->4) linkages in starch.
b. is an important component of saliva and pancreatic juice.
c. catalyzes hydrolysis of α (1->6) linkages in amylopectin.
d. catalyzes hydrolysis of α (1->4) linkages in glycogen.
e. activity is reduced in highly branched regions of polysaccharides and stops four residues from any branch point.
26. The primary storage form of lipid is ____ and it is normally stored in the ____.
a. phospholipid; liver
b. cholesterol; muscles
c. monoacylglycerol; adipocytes
d. triacylglycerols; adipocytes
e. triacylglycerols; liver
Lipid Metabolism
27. Bile salts are important in the initial digestion of triacylglycerols in the intestine because they:
a. Are coenzymes for pancreatic lipase.
b. Convert the inactive lipase into the active form.
c. Emulsify the triacylglycerol globules to produce greater surface area which will increase the activity of the lipase.
d. Activate the cleavage at the C-2 position.
e. Permit greater permeability of the triacylglycerols through the intestinal membrane.
28. Which of the following correctly describes the sequence of events for the conversion of a fatty acid to CO2?
a. Carnitine shuttle, activation to acyl CoA, β-oxidation, TCA cycle
b. Activation to acyl CoA, β -oxidation, carnitine shuttle, TCA cycle
c. Activation to acyl CoA, carnitine shuttle, β -oxidation, TCA cycle
d. TCA cycle, activation to acyl CoA, β -oxidation, carnitine shuttle
e. TCA cycle, activation to acyl CoA, carnitine shuttle, β -oxidation
29. The correct sequence for transport of fatty acyl groups from the cytosol to the matrix is:
A. carnitine acyltransferase I
B. tranaslocase of carnitine and O-acylcarnitine
C. carnitine acyltransferase
D. fatty acyl-CoA synthesis
E.O-acylcarnitine
F. fatty acyl-CoA in matrix
a. C, B, D, A, F, E
b. D, B, F, E, A, C
c. D, E, A, C, B, F
d. D, A, E, B, C, F
e. A, D, E, B, C, F
30. The product of β-oxidation, acetyl-CoA, can be used for all EXCEPT:
a. synthesis of ketone bodies.
b. synthesis of amino acids.
c. catabolism in the TCA cycle.
d. synthesis of glucose.
e. none of the above.
31. For the complete oxidation of a saturated fatty acid with 16 carbons, how many times must the β-oxidation cycle be repeated?
a. 4
b. 7
c. 8
d. 6
e. 16
32. How many NADH are generated from the complete oxidation of palmitoyl-CoA to CO2?
a. 7 from β-oxidation and 24 from the TCA
b. 8 from β-oxidation and 24 from the TCA
c. 7 from β-oxidation and 21 from the TCA
d. 7 from β-oxidation and 28 from the TCA
e. 8 from β-oxidation and 24 from the TCA
33. Fatty acid synthase (FAS) differs from β-oxidation in all of the following ways EXCEPT:
a. occurs in cytosol.
b. uses NADPH for oxidoreductase reactions.
c. acyl carrier protein linked intermediates.
d. all of the enzymes are on one polypeptide.
e. all are true.
34. The committed step in fatty acid biosynthesis, formation of malonyl-CoA, is catalyzed by:
a. Fatty acid synthase.
b. Pyruvate carboxylase.
c. Propionate carboxylase.
d. Acetyl-CoA carboxylase.
e. ATP-citrate lyase.
35. There is no transporter for acetyl-CoA to exit the mitochondria, so the carbons must be converted to ____ for transport to the cytosol.
a. acetone
b. butyrate
c. citrate
d. pyruvate
e. malonate
36. The main source(s) of NADPH for fatty acid biosynthesis is (are):
a. TCA cycle.
b. oxidative phosphorylation.
c. Malic enzyme and the pentose phosphate pathway.
d. The conversion of OAA to malate by malate dehydrogenase.
e. Glycolysis.
37. Reducing equivalents derived from glycolysis in the form of NADH can be transformed into ____ for fatty acid biosynthesis by the combined actions of ____ and ____.
a. NADPH; malate dehydrogenase; malic enzyme
b. NADPH; malate dehydrogenase; malic enzyme
c. ATP; malate dehydrogenase; malic enzyme
d. NADH; glyceraldehyde-3-phosphate dehydrogenase; malate dehydrogenase
e. NADPH; glyceraldehyde-3-phosphate dehydrogenase; malate dehydrogenase
38. The committed step in fatty acid biosynthesis, formation of malonyl-CoA, is catalyzed by:
a. Fatty acid synthase.
b. Pyruvate carboxylase.
c. Propionate carboxylase.
d. Acetyl-CoA carboxylase.
e. ATP-citrate lyase.
39. Which of the following is true regarding fatty acid elongation?
a. Malonyl CoA provides 2 carbons for each round of elongation
b. Two reductions take place with both reactions using NADPH as the source of electrons
c. The fatty acid that is being elongated is attached to CoA
d. Occurs only in cytosol
e. By not performing the second reduction reaction, an unsaturated fatty acid with a cis double bond can be formed
40. Regulation of fatty acid synthesis in humans is affected by all of the following EXCEPT:
a. Malonyl-CoA binding to carnitine acyltransferase inhibits available substrate for β-oxidation.
b. Citrate stimulates acetyl-CoA carboxylase.
c. Acyl-CoAs are inhibitors of acetyl-CoA carboxylase.
d. Insulin receptor binding maintains acetyl-CoA carboxylase in the inactive form.
e. Glucagon promotes phosphorylation and inactivation of acetyl-CoA carboxylase.
41. Which of the following is correctly paired with its effect upon fatty acid synthesis?
a. Palmitoyl CoA: activates
b. Glucagon: activates
c. Insulin: inhibits
d. Citrate: activates
e. NADPH: inhibits
42. Both glycerol and dihydroxyacetone phosphate can serve as precursors for phosphatidic acid. Which enzyme is NOT USED to catalyze reactions in the synthesis of phosphatidic acid from these two precursors?
a. Glycerol kinase
b. Triose phosphate isomerase
c. Acyldihydroxyacetone-P reductase
d. Glycerol-3-phosphate acyltransferase
e. 1-acylglycerol-3-phosphate acyltransferase
43. Which of the following statements regarding phosphorylation of acetyl-CoA carboxylase is correct?
a. Phosphorylation causes activation only in the presence of palmitoyl-CoA
b. Phosphorylation is a result of glucagon binding to its receptor
c. High [citrate] inhibits the phosphorylated form
d. Phosphorylation causes separation of the polymeric form of the enzyme to inactive protomers
e. Both b and d are true Electron Transport Chain and Oxidative Phosphorylation
44. Each of the following is a true statement EXCEPT:
a. Standard free energy change for a redox reaction is related to the standard cell potential
b. Standard free energy change for a redox reaction is related to the number of electrons transferred
c. For redox reactions with negative standard cell potentials, standard free energy change is negative
d. Redox reactions must occur in pairs, where the total number of electrons involved in the oxidation equals the total number involved in the reduction
e. all are true statements
45. All are linked to the electron-transport chain through Complex I accepting electrons from NADH EXCEPT:
a. Gluconeogenesis.
b. Glycolysis.
c. TCA cycle.
d. Fatty acid oxidation.
e. All are true.
46. Complex I and Complex II produce a common product which is:
a. NAD+.
b. FAD.
c. Reduced coenzyme Q.
d. Reduced cyt c.
e. Reduced O2.
47. All are flavoproteins EXCEPT:
a. NADH-CoQ reductase (complex I).
b. Succinate dehydrogenase (complex II).
c. Coenzyme Q-cytochrome c oxidoreductase (complex III).
d. sn-glycerolphosphate dehydrogenase.
e. Fatty acyl-CoA dehydrogenase-transferring protein.
48. Complex III takes up ____ proton(s) on the matrix side of the ____ membrane and releases ____ protons on the intermembrane side for each pair of ____ passed through the Q cycle.
a. two; inner; four; electrons
b. one; inner; two; protons
c. two; inner; four; protons
d. one; outer; two; electrons
e. none are true
49. Which of the following is true regarding proton movement in the mitochondria?
a. Complex III pumps 2 protons across the inner membrane
b. Protons move from the matrix to the inner membrane space via the a and c subunits of ATP synthase to produce ATP
b. 2,4-dinitrophenol moves protons from the inner membrane space to the matrix without ATP synthesis
c. The matrix becomes acidic due to the proton movement coupled to electron transport
d. None of the above
Metabolic Integration
50. The two metabolic roles served by ATP are:
a. Promoting increased reaction speed and dephosphorylation.
b. Changing both Km and Vmax.
c. Allosteric regulation and stoichiometric involvement.
d. Preventing futile cycles and changing Km.
e. None of the above.
51. The reaction, ATP + AMP<--> 2ADP, is catalyzed by:
a. Adenylate phosphorylase.
b. AMP-phosphotransferase.
c. ADP mutase.
d. Adenylate kinase.
e. None are true.
52. During fasting or starvation, the brain:
a. Converts endogenous fatty acids into β-hydroxybutyrate.
b. Utilizes β-hydroxybutyrate from the blood stream.
c. Utilizes amino acids for fuel from degradation of brain protein.
d. Utilizes its glycogen stores as a first responding source of fuel.
e. All of the above.
53. Under strenuous aerobic exercise, which of the following would be true for skeletal muscle?
a. Only glucose will serve as a fuel source
b. Only fatty acids will serve as a fuel source
c. Both glucose and fatty acids will be used as fuel with the use of glucose increasing with the intensity of the exercise
d. Both glucose and fatty acids will be used as fuel with the use of fatty acids increasing with the intensity of the exercise
e. None of the above
Part II.
1) Explain the metabolic features of the following organs:
a. Brain
b. Muscle
c. Liver
2) Determine the hormone response to the metabolic conditions:
a) Well fed
b) Fasting
3) Explain the role of insulin and glucagon on diabetes mellitus and hypoglycemia, respectively.
4) Explain the regulatory process of glycolysis.