Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
23 Cards in this Set
- Front
- Back
The main function of the pentose phosphate pathway is to:
A. give the cell an alternative pathway, should glycolysis fail. B. supply pentoses and NADPH. C. provide a mechanism for the utilization of the carbon skeletons of excess amino acids. D. supply NADH E. supply energy |
B. supply pentoses and NADPH.
|
|
Glucose breakdown in certain mammalian and bacterial
cells can occur by mechanisms other than classic glycolysis. In most of these, glucose-6-phosphate is oxidized to 6- phosphogluconate, which is further metabolized by A. oxidation to a six-carbon dicarboxylic acid B. conversion to 1,6-bisphosphogluconate C. an aldolase-type split to form glycerate and glyceraldehyde-3-phosphate D. an aldolase-type split to form glycolate and erythrose- 4-phosphate E. decraboxylation to produce a ketopentose |
E. decarboxylation to produce a ketopentose
|
|
The oxidation of 3 mol of glucose by the pentose phosphate
pathway may result in the production of A. 3 mol of pentose, 6 mol of NADPH, and 3 mol of CO2 B. 4 mol of pentose, 6 mol of NADPH, and 6 mol of CO2 C. 4 mol of pentose, 3 mol of NADPH, and 3 mol of CO2 D. 3 mol of pentose, 4 mol of NADPH, and 3 mol of CO2 E. 2 mol of pentose, 4 mol of NADPH, and 8 mol of CO2 |
A. 3 mol of pentose, 6 mol of NADPH, and 3 mol of CO2
|
|
Glucose labeled with 14C in different carbon atoms is added to a crude extract of a tissue rich in the enzymes of the pentose phosphate pathway. The most rapid production of 14CO2 will occur when the glucose is labeled in
A. C-5 B. C-1 C. C-6 D. C-3 E. C-4 |
B. C-1
|
|
The respective intermediates for the ribulose-5-P epimerase
and isomerase are A. 1,2 and 3,4 cis-enediols B. 1,2 and 2,3 trans-enediols C. 1,2 and 2,3 cis-enediols D. 2,3 and 1,2 cis-enediols E. 2,3 and 3,4 cis-enediols |
D. 2,3 and 1,2 cis-enediols
|
|
In the transaldolase reaction, sedoheptulose-7-P and glyceraldehyde-3-P react to give
A. erythrose-4-P and fructose-6-P B. ribose-5-P and ribulose-5-P C. fructose-6-P and xylulose-5-P D. xylulose-5-P and ribulose-5-P E. erythrose-4-P and ribulose-5-P |
A. erythrose-4-P and fructose-6-P
|
|
What enzyme in glycogen metabolism is activated by Ca++?
A. cAMP-dependent kinase B. phosphorylase kinase C. debranching enzyme D. glycogen synthase E. branching enzyme |
B. phosphorylase kinase
|
|
A patient is suffering from a glycogen-storage disease where
the structure of glycogen has not been modifed but the concentration of glycogen is above normal. The patient most probably is suffering from an excess of A. phosphorylase B. glucose-6-phosphatase C. _-1,4-glucosidase D. debranching enzyme E. glucagon F. glycogen synthase G. phosphorylase kinase |
F. glycogen synthase
|
|
Phosphorylase kinase is a complex
A. with three non-identical subunits having a calciumbinding protein, and a phosphorylated catalytic subunit B. activated by cAMP C. with phosphorylase as one of its subunits D. with two identical subunits containing pyridoxal-P E. with four non-identical subunits containing two regulatory subunits, a catalytic subunit and calmodulin |
E. with four non-identical subunits containing two regulatory subunits, a catalytic subunit and calmodulin
|
|
Glucagon stimulates formation of cAMP which
A. stimulates protein kinase A which phosphorylates glycogenin. B. stimulates protein kinase A which phosphorylates phosphorylase. C. stimulates protein kinase A which phosphorylates phosphorylase kinase. D. stimulates glycogen synthase kinase 3 which phosphorylates glycogen synthase. E. stimulates phosphorylase kinase which phosphorylates phosphorylase. |
C. stimulates protein kinase A which phosphorylates phosphorylase kinase
|
|
After being stimulated by insulin secretion, protein kinase B activity phosphorylates and
A. increases phosphorylase kinase activity B. increases cAMP concentration C. inactivates protein phsophatase D. inactivates glycogen synthase kinase 3 E. increases Ca++ concentration in muscle F. inactivates cAMP protein kinase activity |
D. inactivates glycogen synthase kinase 3
|
|
Pyridoxal-P acts as a cofactor for one of the glycogenmetabolizing
enzymes by A. activating Pi to attack the glycogen reducing end B. causing a Schiff base intermediate C. acting as an allosteric activator D. contributing its phosphate to form glucose-1-P E. acting as an acid/base catalyst |
E. acting as an acid/base catalyst
|
|
Which hormone or metabolite or protein below is mainly in
muscle and stimulates formation of cAMP to stimulate glycogen breakdown and inhibit glycogen synthesis? A. epinephrine B. calmodulin C. glucagon D. insulin E. glucose |
A. epinephrine
|
|
Which statement describing the function of lipoamide in the pyruvate dehydrogenase complex is false?
A. Lipoamide undergoes oxidation and reduction as part of the enzymatic mechanism. B. Lipoamide is an example of a biological tether involved in substrate channeling. C. Lipoamide is an example of a coenzyme. D. Lipoamide forms a thioester bond during the reaction. E. Lipoamide adds phosphate to E1 to increase its activity. |
E. Lipoamide adds phosphate to E1 to increase its activity.
|
|
Which statement about vitamins, cofactors and coenzymes is false?
A. All coenzymes are either covalently attached or permanently tightly bound to enzyme active sites. B. Metal ions in the active site of enzymes can help catalyze reactions. C. Some coenzymes can act as a biological tether. D. Organic components of coenzymes can be reduced at the active site of enzymes. E. Some coenzymes have organic components that cannot be synthesized by the organism and must be obtained through diet. |
A. All coenzymes are either covalently attached or permanently tightly bound to enzyme active sites.
|
|
Which carbon atom in the molecule shown here is oxidized by the malate dehydrogenase reaction in the TCA cycle?
A. C-3 B. C-1 C. C-2 D. C-4 E. Carbon is not oxidized in this reaction. |
A. C-3
|
|
The _-ketoglutarate dehydrogenase complex requires what coenzyme(s)?
A. FAD B. thiamine pyrophosphate (TPP) C. lipoamide D. coenzyme A E. all of the above |
E. all of the above
|
|
Choose the correct statement describing regulation of the
TCA cycle A. The activity of f-ketoglutarate dehydrogenase is increased by high levels of succinyl-CoA. B. The concentration of oxaloacetate helps control TCA cycle activity. C. The activity of citrate synthase is increased by a decreased ratio of NAD+/NADH. D. The activity of isocitrate dehydrogenase is decreased by increasing Ca2+ levels. E. The activity of fumarase is increased by high levels of ATP. |
B. The concentration of oxaloacetate helps control TCA
cycle activity. |
|
Which statement about the thermodynamics of the TCA cycle is false?
A. Under standard state conditions, the malate dehydrogenase reaction is highly exergonic. B. The regulated enzymes in the TCA cycle are those that are endergonic. C. Under cellular conditions, the majority of reactions in the TCA cycle are near equilibrium. D. All the reactions of the TCA cycle must have negative _G's for the cycle to function. E. Due to the equilibrium constants of the malate dehydrogenase and citrate synthase reactions, the concentration of oxaloacetate in mitochondria is very high. |
C. Under cellular conditions, the majority of reactions in
the TCA cycle are near equilibrium. |
|
Which statement about pyruvate carboxylase is false?
A. This enzyme's activity increases when high levels of acetyl-CoA are present. B. This enzyme is part of gluconeogenesis. C. This enzyme can replenish TCA-cycle intermediates when the TCA cycle is functioning in anabolic mode. D. This enzyme requires biotin in its active site. E. This enzyme uses hydrolysis of a thioester bond to drive the reaction. |
E. This enzyme uses hydrolysis of a thioester bond to drive
the reaction. |
|
The unique reactions in the glyoxylate cycle are
A. succinate dehydrogenase and isocitrate lyase B. malate enzyme and isocitrate lyase C. malate dehydrogenase and isocitrate dehydrogenase D. malate enzyme and citrate synthase E. aconitase and citrate synthase |
B. malate enzyme and isocitrate lyase
|
|
Coordinated regulation of the TCA and glyoxylate cycle occurs
at what enzyme levels in the two cycles? A. aconitase and isocitrate dehydrogenase B. malate enzyme and _-ketoglutarate dehydrogenase C. malate enzyme and citrate synthase D. isocitrate dehydrogenase and isocitrate lyase E. isocitrate lyase and malate dehydrogenase |
D. isocitrate dehydrogenase and isocitrate lyase
|
|
The products of the isocitrate lyase reaction are
A. succinate and glyoxylate B. glyoxalate and malate C. acetyl-CoA and oxaloacetate D. succinate and glycoaldehyde E. malate and acetyl-CoA |
A. succinate and glyoxylate
|