Carbohydrate Metabolism

Question 1

What are the primary results of the pentose phosphate pathway

Answer 1

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

Question 2

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

Answer 2

nucleotides, coenzymes

Question 3

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

Answer 3

aromatic amino acids

Question 4

What are the three key enzymes in the pentose phosphate pathway

Answer 4

glucose-6-P dehydorgenase, transketolase and transaldolase

Question 5

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

Answer 5

generates NADPH

Question 6

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

Answer 6

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

Question 7

What is the reaction for the pentose phosphate pathway

Answer 7

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

Question 8

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

Answer 8

carbon shuffle

Question 9

Reactions in the nonoxidative pathway are catalyzed by what two enzymes

Answer 9

transketolase and transaldolase

Question 10

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

Answer 10

gluconeogenic

Question 11

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

Answer 11

NAD+ and NADPH

Question 12

When NADP+ is high, what pathway is favoured?

Answer 12

penthose phosphate pathway

Question 13

when NADPH is high, what pathway is favoured?

Answer 13

glycolysis

Question 14

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

Answer 14

primaquine or vicine

Question 15

what is gluconeogenesis

Answer 15

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

Question 16

what to plants use gluconeogenesis for

Answer 16

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

Question 17

How many irreversible steps in gluconeogenesis

Answer 17

3

Question 18

What are the irreverisble steps in gluconeogenesis

Answer 18

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

Question 19

What are the four sources of carbon in glycolysis

Answer 19

lactate, amino acids, glycerol and CO2

Question 20

What is the overall net reaction of gluconeogenesis

Answer 20

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

Question 21

What are the key enzymes in gluconeogenesis

Answer 21

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

Question 22

T or F: Gluconeogenesis is expensive

Answer 22

T

Question 23

T or F: Glycolysis and Gluconeogenesis are reciprocally correlated

Answer 23

T

Question 24

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

Answer 24

a consumption of ATP and GTP and a production of heat

Question 25

Hexokinase is a _____ enzyme

Answer 25

cytoplasmic

Question 26

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

Answer 26

lumen of the ER

Question 27

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

Answer 27

GLUT2

Question 28

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

Answer 28

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

Question 29

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

Answer 29

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

Question 30

the activity of PFK-1 increases in presence of ___________

Answer 30

fructose 2,6BP

Question 31

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

Answer 31

fructose 1,6 BP

Question 32

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

Answer 32

PFK2/FBPase2

Question 33

What is the Cori Cycle

Answer 33

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

Question 34

what is glycogen

Answer 34

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

Question 35

What are the three key reactions in glycogen degredation and synthesis

Answer 35

glycogen phosphorlylase, glycogen synthase, glycogen branching and debranching enzyme

Question 36

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

Answer 36

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

Question 37

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

Answer 37

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

Question 38

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

Answer 38

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

Question 39

what is the net reaction for glycogen degredation

Answer 39

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

Question 40

what is the net reaction for glycogen synthesis

Answer 40

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

Question 41

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

Answer 41

PLP

Question 42

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

Answer 42

UDP

Question 43

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

Answer 43

7

Question 44

R state conformation of glycogen synthase is __________

Answer 44

unphosphorylated

Question 45

T state conformation of glycogen synthase is _________

Answer 45

phosphorylated

Question 46

what leads to the phosphorylation of glycogen synthase

Answer 46

epinephrine and glucagon

Question 47

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

Answer 47

glycogen phosphorylase and synthase