biochem final questions 14/15

which enzyme is used in both glycolysis and gluconeogenesis?

glucose 6-phosphotase

hexokinase

pyruvate kinase

3-phosphoglycerate kinase

phosphofructokinase-2

3-phosphoglycerate kinase

which cofactor participates directly in most of the oxidation reduction reactions in the fermentation of glucose to lactate?

NAD+/NADH

ADP

glyceraldehyde 3-phosphate

FAD/FADH2

ATP

NAD+/NADH

in humans, the cori cycle shifts part of the metabolic burden of active muscle to the liver. Which two metabolic pathways are involved in this cycle?

PPP and gluconeogenesis

glycolysis and gluconeogenesis

gluconeogenesis and the calvin cycle

glycolysis and the PPP

none of the above

glycolysis and gluconeogenesis

which process does not occur in the steps of glycolysis between glyceraldehyde 3-phosphate and phisphoenolpuruvate?

phosphoryl transfer

isomerization

ATP synthesis

hydration reaction

oxidation

hydration reaction

which of the following is NOT a key enzyme for regulating glucose breakdown

pyruvate kinase

phosphoglycerate kinase

all choices are correct

phosphofructokinase-1

hexokinase

phosphoglycerate kinase

which statement about gluconeogenesis is false

it requires metabolic energy

for starting materials, it can use carbon skeletons derived from certain amino acids

it consists entirely of the reactions of glycolysis operating in the reverse direction

it employs the enzyme glucose 6-phosphatase

it is one of ways that mammals maintain normal blood glucose levels between meals

it consists entirely of the reactions of glycolysis operating in the reverse direction

why is anaerobic fate of pyruvate necessary in skeletal muscle

the anaerobic process directly generates additional ATP for working muscle

it allows for the reoxidation of NADH to NAD+ as NAD+ is in limited supply during anaerobic conditins

it is required to maintain the reducing environment of the cytosol

it decreases the pH of skeletal muscle, thereby increasing release of oxygen from myoglobin

none of the answers are correct

it allows for the reoxidation of NADH to NAD+ as NAD+ is in limited supply during anaerobic conditins

which enzyme that is involved in the flow of carbon from glucose to lactate (glycolysis) is not also involved in the reversal of this flow (gluconeogenesis)

phosphoglucose isomerase

3-phosphoglycerate kinase

enolase

phosphofructokinase-1

aldolase

phosphofructokinase-1

animals store a great deal more energy in fats than in glycogen. fats also store more energy per gram than glycogen. which is a reason for having some energy stored in glycogen rather than using fats alone.

glycogen is for longer term energy storage for cases such as prolonged starvation

glycogen can be transported into the blood more easily than fats

energy released from glycogen is highly targeted for use in particular tissues associated with the lymphatic system

glucose can be released very quickly from glycogen to provide energy

glucose can be released very quickly from glycogen to provide energy

is glycogen phosphorylase activated, inhibited, or unaffected in response to an insulin signal in a skeletal muscle

inhibited

the breakdown of glycogen to glucose 1-phosphate is called

neoglycogenesis

glycogen anabolism

deglycogenization

glycogenolysis

glycogenolysis

after a meal rich in carbos, which change would not be expected in a normal human

increased glucose uptake in monocytes via GLUT4

increased activity of liver enzyme hexokinase IV

increased secretion of pancreatic hormone insulin

decreased activity of glycogen synthase kinase 3 in monocytes and hepatocytes

increased activity of glucose 6-phosphate in hepatocytes

increased activity of glucose 6-phosphate in hepatocytes

which statement is true for glycogen granules in liver cells

each particle may contain up to 55000 glucose molecules

glycogen is stored in the cytosol as granules

all of the statements are true

liver glycogen granules account for up to 10% of the weight of the liver

all of the statements are true

the metabolic function of the pentose phosphate path is to

generate NADPH and pentoses for the biosynthesis of fatty acids and nucleic acids

synthesize phosphorus pentoxide

provide intermediates for the citric acid cycle

act as a source of ADP for biosynthesis

participate in oxidation reduction reactions

generate NADPH and pentoses for the biosynthesis of fatty acids and nucleic acids

which products of glycolysis serve to store energy

ATP and NADH

fructose 1,6-bisphosphate, 1,3-bisphosphoglycerate, and phosphoenolpyruvate

ATP, NADH, 1,3-bisphosphoglycerate, phosphoenolpyruvate

1,3-bisphosphoglycerate and phosphoenolpyruvate

fructose 1,6-bisphosphate

ATP and NADH

which reaction in glycolysis requires ATP as a substrate

phosphyglycerate kinase

glyceraldehyde 3-phosphate dehydrogenase

aldolase

hexokinase

pyruvate kinase

hexokinase

cellular isozymes of pyruvate kinase are allosterically inhibited by _____ concentrations of _____

low, ATP

high, AMP

high, ATP

high, citrate

low, acetyl-CoA

high, ATP

the anaerobic conversion of one molecule of glucose to two molecules of lactate by fermentation is accompanied by a net gain of

two molecules of NADH

two molecules of ATP

none of the answers are correct

one molecule of ATP

one molecule of NADH

two molecules of ATP

which is a transcription factor that is involved in regulating the transcription of glycolytic or gluconeogenic enzymes?

sterol response element binding protein

phosphofructokinase-2

mRNA binding protein

acetyl-CoA binding element

carbohydrate response element binding protein

carbohydrate response element binding protein

glucokinase (hexokinase IV) differs from hexokinase (hexokinase I)

to allow the pancrease to trigger insulin release when blood sugar levels are low

so that the liver does not compete with other tissues for glucose when glucose levels are high

by requiring larger concentrations of glucose before reaching maximal activity

to allow the liver to export free glucose to the bloodstream when blood sugar levels drop

by having a higher affinity for glucose and not being inhibited by high levels of glucose

by requiring larger concentrations of glucose before reaching maximal activity

two reactions, extra to the ten reactions of glycolysis, are involved in ethanol fermentation by yeast under anaerobic conditions. what is the purpose served by these two reactions in the metabolism of yeast cells

they are required to reoxidize limited amounts of NADH

they are required to ensure a net oxidation of glucose

they are required to both ensure a net oxidation of glucose and sustain glycolysis, ensuring ATP production

they are required to sustain glycolysis, ensuring ATP production

they are required to both re-oxidize limited amounts of NADH and sustain glycolysis, ensuring ATP production

they are required to both re-oxidize limited amounts of NADH and sustain glycolysis, ensuring ATP production

the enzyme phosphoglycerate mutase is characterized by which enzyme class?

transferase

lyase

isomerase

ligase

oxioreductase

isomerase

glycogen synthase and glycogen phosphorylase are both regulated by phosphorylation. which answer choice most accurately described the process

phosphorylation of glycogen phosphorylase decreases the rate of glycogen breakdown while phosphorylation of glycogen synthase increases the rate of glycogen synthesis

the phosphorylation of both enzymes increases their activity

glycogen phosphorylase phosphorylates glycogen synthase

the phosphorylation of both enzymes decreases their activity

phosphorylation of glycogen phosphorylase increases the rate of glycogen breakdown while phosphorylation of glycogen synthase decreases the rate of glycogen synthesis

phosphorylation of glycogen phosphorylase increases the rate of glycogen breakdown while phosphorylation of glycogen synthase decreases the rate of glycogen synthesis

which substrate cannot contribute to net gluconeogenesis in mammalian liver

palmitate

glutamate

a-ketoglutarate

pyruvate

alanine

palmitate

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 NAD+ is

pyruvate → lactate

isocitrate → a-ketoglutarate

oxaloacetate → malate

dihydroxyacetone phosphate → glycerol 3-phosphate

glucose 6-phosphate → fructose 6-phosphate

pyruvate → lactate

which statement about the PPP is correct

it generates 6 molecules of CO2 for each molecule of glucose consumed

it is present in plants but not animals

it generates 36 molecules of ATP per molecule of glucose consumed

it is a reductive pathway; it consumes NADH

it provides precursors for the synthesis of nucleotides

it provides precursors for the synthesis of nucleotides

in glycolysis, fructose 1,6-bisphosphate is converted to two products with a deltaG of 23.8kj/mol. under what conditions will the free energy change be negative, enabling the reaction to proceed to the right?

under standard conditions

when there is a high concentration of fructose 1,6-bisphosphate relative to the concentration of products

when there is a high concentration of products relative to the concentration of fructose 1,6-bisphosphate

the reaction will not go to the right spontaneously under any conditions

when there is a high concentration of fructose 1,6-bisphosphate relative to the concentration of products

the PPP is multifunctional with metabolic flexibility. which statement is false with respect to this pathway?

it generates NADH for reductive biosynthesis

all the enzymes in this pathway are located in the cytosol

all intermediates in this pathway are phosphorylated

the activities of transaldolase and transketolases link this pathway to gluconeogenesis

in erythrocytes, this pathway is required to maintain glutathione in a reduced state

it generates NADH for reductive biosynthesis

ethanol is produced by yeast under anaerobic conditions. this is accomplished by 2 reactions beyond the 10 reactions of glycolysis. what is the purpose served by these 2 reactions in the metabolism of yeast cells

they are required to produce NADPH

they are required to reoxidize NADH

they are required to ensure a net oxidation of glucose

they are required to sustain gluconeogenesis

they are required to reoxidize NADH

what is the net yield of ATP produced by the anaerobic fermentation of one molecule of sucrose in monocytes

4

2

3

6

8

4

the oxidation of 3 mol of glucose by the PPP may result in the production of

4 mol of pentose, 6 mol of NADPH, 6 mole of CO2

4 mol of pentose, 3 mol of NADPH, 3 mole of CO2

3 mol of pentose, 4 mol of NADPH, 3 mole of CO2

3 mol of pentose, 6 mol of NADPH, 3 mole of CO2

2 mol of pentose, 4 mol of NADPH, 8 mole of CO2

3 mol of pentose, 6 mol of NADPH, 3 mole of CO2

which statement is not associated with controlling the rate of glycogen synthesis in the liver

insulin induces the synthesis of hexokinase IV

glucagon inhibits the activity of glycogen synthase

insulin activates phosphoprotein phosphatase I

insulin activates glycogen synthase kinase 3

insulin activates glycogen synthase kinase 3

in glycogen ___ glycosidic bonds occur at branch points, while all others are ___ glycosidic bonds

all glycosidic bonds in glycogen are (a1→4)

(b1→6) (a1→4)

(a1→6) (a1→4)

(a1→4) (a1→6)

(b1→4) (a1→4)

(a1→6) (a1→4)

which is true about the core of glycogen granules in the liver

the single nonreducing end of glucogen is at the core

the core contains a glycogenin dimer

the core is composed of tightly would glycogen helical structures

the core is the same as the rest of the granule

the core contains a glycogenin dimer

glycogenin

regulates the synthesis of glycogen

is a primer on which new glycogen chains are initiated

is the enzyme responsibly for forming branches in glycogen

catalyzes the conversion of starch into glycogen

is the gene that encodes glycogen synthase

is a primer on which new glycogen chains are initiated

wich reaction in glycolysis is a ketose to aldose isomerization

phosphoglycerate mutase

enolase

hexokinase

aldolase

triose phosphate isomerase

triose phosphate isomerase

what role(s) does ATP have with respect to PFK-1?

only allosteric inhibitor

substrate and allosteric inhibitor

substrate and allosteric activator

only substrate

only allosteric activator

substrate and allosteric inhibitor

which enzyme is used in both glycolysis and gluconeogenesis

glucose 6-phosphatase

pyruvate kinase

3-phosphoglycerate kinase

hexokinase

phosphofructokianse-2

3-phosphoglycerate kinase

in humans, gluconeogenesis

helps to reduce blood glucose after a carb rich meal

requires the enzyme hexokinase

is essential in the conversion of fatty acids to glucose

can result in the conversion of protein into blood glucose

is activated by the hormone insulin

can result in the conversion of protein into blood glucose

glycogen is converted to monosaccharide units by

glucose 6-phosphatase

glycogen synthase

glycogen phosphorylase

glycogenase

glucokinase

glycogen phosphorylase

the conversion of one molecule of fructose 1,6-bisphosphate to two molecules of pyruvate by the glycolytic pathway results in a net formation of ___ molecule(s) of ___ and ___ molecule(s) of ATP.

one, NAD+, two

two, NADH, four

two, NADH, two

two, NAD+, four

one, NADH, one

two, NADH, four

which reaction in glycolysis produces ATP as a product

aldolase

glyceraldehyde 3-phosphate dehydrogenase

phosphofructokinase-1

hexokinase

pyruvate kinase

pyruvate kinase

which statement is true of glycogen synthase

it catalyzes addition of glucose residues to the nonreducing end of a glycogen chain by formation of (a1→4) bonds

activation of the enzyme involves phosphorylation

the enzyme has measurable activity only in the liver

it uses glucose 6-phosphate as donor of glucose units

it catalyzes addition of glucose residues at branch points by formation of (a1→6) bonds

it catalyzes addition of glucose residues to the nonreducing end of a glycogen chain by formation of (a1→4) bonds

which statement regarding regulation of glycolysis and gluconeogenesis is false

the cellular concentration of fructose 2,6-bisphosphate is determined by a bifunctional enzyme that is hormonally regulated

hexokinase IV and glucose 6-phosphatase are transcriptionally regulated in hepatocytes

bindnig of fructose 2,6-bisphosphate to phosphofructokinase-1 reduces the affinity of this enzyme for citrate

phosphofructokinase-1 and fructose 1,6-bisphosphatase are recpirocally regulated by the allosteric regulator fructose 2,6-bisphosphate

phosphofructokinase-1 and fructose 1,6-bisphosphatase are prevented from forming a futile cycle by reversible covalent modification

phosphofructokinase-1 and fructose 1,6-bisphosphatase are prevented from forming a futile cycle by reversible covalent modification

which enzyme phosphorylates three serines of glycogen synthase A to convert it to glycogen synthase b?

phosphoprotein phosphorylase I

AMP-activated protein kinase

caesin kinase II

glycogen synthase kinase 3

insulin

glycogen synthase kinase 3