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CH350 > Carbohydrate Metabolism > Flashcards

Carbohydrate Metabolism Flashcards

1
Q

What are the primary results of the pentose phosphate pathway

A

reduce 2 molecules of NADP+ to NADPH for each glucose-6-P that is oxidatively decarboxylized to ribulose 5-P

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2
Q

Production of ribulose-5-P is used in the synthesis of ______ and some ________

A

nucleotides, coenzymes

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3
Q

Production of erythrose-4-phosphate is used in the synthesis of ______ ______ ____

A

aromatic amino acids

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4
Q

What are the three key enzymes in the pentose phosphate pathway

A

glucose-6-P dehydorgenase, transketolase and transaldolase

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5
Q

What does the oxidative phase of pentose phosphate pathway accomplish for the cell

A

generates NADPH

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6
Q

what does the nonoxidative phase of the pentose phosphate pathway accomplish for the cell

A

interconverts C3 - C7 monosaccharides to produce ribulose-5-P for nucleotide synthesis

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7
Q

What is the reaction for the pentose phosphate pathway

A

6 glucose-6-P + 12NADP+ +6H2O –> 4 fructose-6-P + 2 glyceraldehyde-3-P + 12 NADPH + 12H + 6 CO2

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8
Q

6 ribulose-5-P is converted to 4 fructose-6-P and 2 glyceradlehyde-3-P using _____ _____

A

carbon shuffle

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9
Q

Reactions in the nonoxidative pathway are catalyzed by what two enzymes

A

transketolase and transaldolase

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10
Q

Glucose-6-P regenerated from fructose-6-P and g3P by enzymes in _________ pathway

A

gluconeogenic

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11
Q

Glucose-6-P dehydrogenase activity is allosterically regualated by _____ and ____ ratios

A

NAD+ and NADPH

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12
Q

When NADP+ is high, what pathway is favoured?

A

penthose phosphate pathway

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13
Q

when NADPH is high, what pathway is favoured?

A

glycolysis

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14
Q

G6PD deficiency reduces ability to detoxify oxygen radicals that result from the metabolism of _______ or ______

A

primaquine or vicine

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15
Q

what is gluconeogenesis

A

multistep process in which glucose is produced from lactate pyruvate or oxaloacetate from noncarbohydrate sources for export to other tissues

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16
Q

what to plants use gluconeogenesis for

A

to convert G3P into glucose which is used to make sucrose and starch

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17
Q

How many irreversible steps in gluconeogenesis

A

3

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18
Q

What are the irreverisble steps in gluconeogenesis

A

1- converion of PEP via oxaloacetate catalyzed by pyruvate carboxylase
2- dephosphorylation of fructose 1,6 BP by fructose 1,6 BP-1
3- dephosporylation of glucose-6-P by glucose-6, phosphatase

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19
Q

What are the four sources of carbon in glycolysis

A

lactate, amino acids, glycerol and CO2

20
Q

What is the overall net reaction of gluconeogenesis

A

2 pyruvate+2NADH + 4ATP + 2GTP + 2H2O –> glucose + 2NAD + 2H+ + 2ADP + 2GDP + 6Pi

21
Q

What are the key enzymes in gluconeogenesis

A

pyruvate carboxylase, phosphoenol pyruvate carboxykinase, FBPase-1, glucose-6-phospotase

22
Q

T or F: Gluconeogenesis is expensive

A

T

23
Q

T or F: Glycolysis and Gluconeogenesis are reciprocally correlated

A

T

24
Q

If glycolysis and gluconeogenesis were both allowed to proceed at high rates, what would be the result

A

a consumption of ATP and GTP and a production of heat

25
Q

Hexokinase is a _____ enzyme

A

cytoplasmic

26
Q

glucose-6-phosphotase is localized in the _____ of the ___

A

lumen of the ER

27
Q

_______ transport protein in the plasma membrane of liver cells permits glucose exchange between the inside and outside of the cell

A

GLUT2

28
Q

What happens in a low energy environment (High AMP and ADP)

A

increases flux thoguh stimulation of PFK-1 activity and inhibition of gluconeogenic enzymes pyruvate carboxylase, PEPCK and FBPase-1

29
Q

What happens in a high energy environment (Metabolites in citric acid cycle accumulate)

A

stimulates gluconeogenesis by acetyl-CoA and citrate, activates pyruvate carboxylase and FBPase 1

30
Q

the activity of PFK-1 increases in presence of ___________

A

fructose 2,6BP

31
Q

addition of fructose 2,6BP to enzyme reactions containing FBPase1 decreases its affinity for __________

A

fructose 1,6 BP

32
Q

Hormonal regulation of glycolysis and gluconeogenesis depends of the phosphoyrlation state of the dualfuction enzyme ____/______

A

PFK2/FBPase2

33
Q

What is the Cori Cycle

A

converts lactase in muscle cells through gluconeogenesis in liver cells, cost of 4 ATP

34
Q

what is glycogen

A

a polysaccharide fo glucose that is a storage form of glucose in animals fungi and bacteria

35
Q

What are the three key reactions in glycogen degredation and synthesis

A

glycogen phosphorlylase, glycogen synthase, glycogen branching and debranching enzyme

36
Q

what are the three key reactions for reverisble glycogen degredation and synthesis

A

1- glycogen phosphorylase releases glucose-1-phosphate from glycogen
2-glycogen synthase adds glucose to nonreducing ends of glycogen
3- glycogen branching and debranching enzymes create multiple nonreducing ends

37
Q

What does glycogen degredation and synthesis do for animals in the liver

A

is used as a short term energy source by storing and release glucose in response to blood glucose levels

38
Q

What does glycogen degredation and synthesis do for animals in the muscles

A

provides a readily available source of glucose in both anaerobic and aerobic exercise

39
Q

what is the net reaction for glycogen degredation

A

glycogen (n units of glucose) + Pi –> glycogen (n-1 units of glucose) + glucose 1 phosphate

40
Q

what is the net reaction for glycogen synthesis

A

glycogen (n units of glucose) + glucose 1 phosphate + ATP + H2O –> glycogen (n-1 units of glucose) + ADP + 2 Pi

41
Q

glycogen phosphorylase catalyzes a phosproylase reaction using the enzyme ___ to generate glucose-1-P

A

PLP

42
Q

glycogen synthase catalyzes a reaction using ___-glucose residues one at a time to the nonreducing ends of oxygen

A

UDP

43
Q

glycogen binding enzyme creates a new alpha 1,6 branch point and new nonreducing end by transferring __ glucose residues from the end of a growing chain

A

7

44
Q

R state conformation of glycogen synthase is __________

A

unphosphorylated

45
Q

T state conformation of glycogen synthase is _________

A

phosphorylated

46
Q

what leads to the phosphorylation of glycogen synthase

A

epinephrine and glucagon

47
Q

Hormonal regulation of glycogen is mediated by phosphorylation and dephosphoylation of _______

A

glycogen phosphorylase and synthase

CH350 (12 decks)

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