BICH 409 Exam 4

what is a general feature of the lipid bilayer in all biological membranes?

individual lipid molecules are free to diffuse laterally in the surface of the bilayer

a deficiency of which enzyme would lead to hemolytic anemia and decreased affinity of Hb for oxygen?

hexokinase?

GLYCOLYSIS SELF TEST

t/f: glycolysis is an anabolic pathway

false

catabolic

t/f: glycolytic enzymes are found in the mitochondria

false

cytosol

t/f: glycolysis is an exergonic process

true

t/f: pyruvate carboxylase is found only in the mitochondria

true

t/f: one of the functions of the pentose phosphate pathway is to generate NADH

false

NADPH

the last reaction of glycolysis is catalyzed by:

pyruvate kinase

which intermediate of glycolysis is a high energy compound?

1,3-BPG

the conversion of glyceraldehyde 3-phosphate into 1,3-BPG involves:

the formation of a covalent thioester intermediate

the conversion of dihydroxyacetone phosphate into glyceraldehyde 3-phosphate involves:

an enediol intermediate

what are the final products of aerobic catabolism of glucose?

CO2 and H2O

the 9th reaction of glycolysis is catalyzed by:

enolase

what is not a substrate of hexokinase?

galactose

the first committed step of glycolysis is catalyzed by:

phosphofructokinase-1

the first committed step of the pentose phosphate pathway is catalyzed by:

glucose-6-P-dehydrogenase

the first reaction in glycolysis that results in the formation of ATP is catalyzed by:

phosphoglycerate kinase

the conversion of 3-phosphoglycerate into 2-phosphoglycerate involves:

a phosphorylated histidine residue

enolase catalyzes:

the dehydration of 2-phosphoglycerate

the three irreversible reactions of glycolysis are catalyzed by:

hexokinase, phosphofructokinase-1, and pyruvate kinase

lactate produced by anaerobic muscle tissue is:

carried by the blood to the liver for gluconeogenesis back to glycogen

the oxidation of one mole of glucose by anaerobic glycolysis yields a net of:

2 moles lactate, 2 moles ATP

under anaerobic conditions, skeletal muscle generates lactate from pyruvate to:

regenerate NAD+ for further glycolysis

the reaction catalyzed by glyceraldehyde-3-phosphate dehydrogenase involves:

an enediol intermediate

glucokinase:

has a Km for glucose considerably greater than the normal blood glucose concentration

which enzymes are used in both gluconeogenic and glycolytic pathways?

phosphoglycerate kinase

which 2 glycolytic enzymes catalyze a substrate level phosphorylation?

phosphoglycerate kinase and pyruvate kinase

class I aldolases are characterized by:

a schiff base intermediate

the pentose phosphate pathway:

produces NADPH for anabolic reductive biosynthesis

an important reason to phosphorylate glucose is the large (+/-) free energy change is important to getting the glycolytic pathway started

negative

why is gluconeogenesis important?

maintaining blood glucose levels during the overnight fast

which reaction is catalyzed by transketolase?

sedoheptulose-7-P + glyceraldehyde-3-P <--> xyulose-5-P + ribose-5-P

the enzyme fructose 1,6-bisphosphate is:

activated by citrate

which reaction is unique to gluconeogenesis?

oxaloacetate --> PEP

transketolase is an enzyme that catalyzes:

the thiamine pyrophosphate dependent transfer of 2-carbon units to an aldose

gluconeogenesis is the synthesis of:

glucose from noncarbohydrate precursors

gluconeogenesis requires a total of __ NTPs

6

the endoplasmic reticulum bound enzyme that hydrolyzes glucose-6-phosphate to glucose in the liver is:

glucose-6-phosphatase

which reaction is catalyzed by transaldolase?

erythrose-4-P + fructose-6-P <--> sedoheptulose-7-P + glyceraldehyde-3-P

phosphofructokinase-1 of the liver is allosterically activated by:

fructose-2,6-bisphosphate and AMP

the conversion of 1 mole of fructose into 2 moles pyruvate by glycolysis in the liver cells results in the net formation of:

2 moles NADH and 2 moles ATP

pyruvate kinase is inactivated by:

citrate

what are the precursors for gluconeogenesis?

lactate, glycerol, pyruvate, oxaloacetate

what is true about glycogen?

glycogen catabolism generates 90% glucose 1-P and 10% glucose

fructose-1,6-bisphosphate is:

allosterically inactivated by fructose-2,6-bisphosphate

GLYCOGEN METABOLISM SELF TEST

in terms of energy yield, phosphorolysis is preferable to hydrolysis in the breakdown of glycogen because:

glucose-1-phosphate yields more net ATP than free glucose yields when catabolized into pyruvate

the extracellular "first messenger" that initiates the cyclic AMP dependent phosphorylation cascade in the muscles is:

epinephrine

glycogen synthase catalyzes which reaction?

UDP-glucose + glycogen(n) --> glycogen(n+1) + UDP

glycogen is broken down by glycogen phosphorylase to yield glucose-1-P

if glucose-1-P passes through glycolysis to give pyruvate, the net yield is:

3 moles ATP and 2 moles NADH per mole glucose-1-P

the mechanism of the epimerization of ribulose-5-phosphate into xylulose-5-phosphate by the enzyme ribulose-5-phosphate epimerase involves:

an enediolate intermediate

the phosphorylation of glycogen synthase and glycogen phosphorylase:

deactivates glycogen synthase while activating glycogen phosphorylase

glycogen synthase requires pyridoxal phosphate as a cofactor

false

doens't require a cofactor

glycogen stored in the muscles cannot contribute directly to blood glucose levels because:

muscle tissue lacks glucose-6-phosphatase

glycogen synthesis requires ___ to activate glucose-1-phosphate

UTP

glycogen phosphorylase catalyzes which reaction?

glycogen(n+1) + Pi --> glycogen(n) + alpha-glucose-1-P