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biochem term 2 quiz 1 > gluconeogenesis > Flashcards

gluconeogenesis Flashcards

1
Q

what can the precursors of gluconeogenesis be?

A

lactate
AA
glycerol - from triglycerides

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2
Q

glycolysis is usually irreversable. why can gluconeogenesis occur?

A

the liver has a set of enzymes that bypass the non-reversible reactions of glycolysis

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3
Q

what enzymes are involved in the conversion of pyruvate to PEP?

A

pyruvate carboxylase and PEP carboxylase

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4
Q

what is the energy input needed to convert pyruvate to PEP?

A

2 ATP equivalents

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5
Q

where does the pyruvate carboxylase reaction occur?

A

in the mitochondria

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6
Q

what does the pyruvate carboxylase enzyme do? what does it use to do so and what are the products? are there cofactors?

A

uses ATP to attach CO2 to pyruvate
requires biotin as a cofactor
acetyl-coA is required to activate enzyme

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7
Q

what does PEP carboxykinase do? what does it use to do so?

A

uses GTP to phosphorylate decarboxylate axaloacetate in process of converting pyruvate to PEP

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8
Q

where does the PEP carboxylase reaction occur?

A

in the cytoplasm

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9
Q

is the PEP carboxylase reaction reversible?

A

no

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10
Q

what does malate dehydrogenase do? why is this necessary?

A

convert oxaloacetate to malate so that the sugar may enter the mitochondria, where it’s then converted to oxaloacetate again whe out of the mitochondria
necessary for gluconeogenesis because part of reaction (pyruvate carboxylase part) takes place in mitochondria, while the next step (PEP carboxylase) takes place in the cytoplasm but oxaloacetate can’t cross the mitochondrial membrane

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11
Q

what enzymes does gluconeogenesis use?

A

the reversible enzymes of glycolysis in the reverse direction
fructose-1,6-bisphosphate
G-6-phosphatase

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12
Q

what does fructose-1,6-bisphosphate do?

A

converts fructose-1,6-bisphosphate to F-6-P

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13
Q

what regulates fructose-1,6-bisphosphate?

A

citrate and APT activate

F-2,6-bisphosphate and ADP inhibit

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14
Q

what does G-6-phosphatase do? why is this enzyme necessary?

A

in gluconeogenesis
coverts G-6-P to glucose
necessary because hexokinase and glucokinase are not reversible

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15
Q

what are the steps of the cori cycle? why is it necessary

A

lactate converted to glucose in the liver
glucose converted to lactate in muscle
necessary so that lactate is converted to glucose so the brain can use it

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16
Q

where does glycerol come from?

A

the lipolysis of TG

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17
Q

what are the energy requirements of gluconeogenesis from glycerol?

A

ATP

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18
Q

what does pyruvate dehydrogenase (PDH) do?

A

usually converts pyruvate to Acetyl CoA but can also convert lactate to oxaloacetate

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19
Q

what are the three enzymes that make up PDH?

A

pyruvate decarboxylase
dihydrolipyltransacetylase
dihydrolipoyl dehydrogenase

20
Q

what are the cofactors that PDH uses?

A 
NAD+
Thiamine pyrophosphate (TPP)
Lipoic acid
FAD
coenzyme A
21
Q

what can the precursors of gluconeogenesis be?

A

lactate
AA
glycerol - from triglycerides

22
Q

glycolysis is usually irreversable. why can gluconeogenesis occur?

A

the liver has a set of enzymes that bypass the non-reversible reactions of glycolysis

23
Q

what enzymes are involved in the conversion of pyruvate to PEP?

A

pyruvate carboxylase and PEP carboxylase

24
Q

what is the energy input needed to convert pyruvate to PEP?

A

2 ATP equivalents

25
Q

where does the pyruvate carboxylase reaction occur?

A

in the mitochondria

26
Q

what does the pyruvate carboxylase enzyme do? what does it use to do so and what are the products? are there cofactors?

A

uses ATP to attach CO2 to pyruvate
requires biotin as a cofactor
acetyl-coA is required to activate enzyme

27
Q

what does PEP carboxykinase do? what does it use to do so?

A

uses GTP to phosphorylate decarboxylate axaloacetate in process of converting pyruvate to PEP

28
Q

where does the PEP carboxylase reaction occur?

A

in the cytoplasm

29
Q

is the PEP carboxylase reaction reversible?

A

no

30
Q

what does malate dehydrogenase do? why is this necessary?

A

convert oxaloacetate to malate so that the sugar may enter the mitochondria, where it’s then converted to oxaloacetate again whe out of the mitochondria
necessary for gluconeogenesis because part of reaction (pyruvate carboxylase part) takes place in mitochondria, while the next step (PEP carboxylase) takes place in the cytoplasm but oxaloacetate can’t cross the mitochondrial membrane

31
Q

what enzymes does gluconeogenesis use?

A

the reversible enzymes of glycolysis in the reverse direction
fructose-1,6-bisphosphate
G-6-phosphatase

32
Q

what does fructose-1,6-bisphosphate do?

A

converts fructose-1,6-bisphosphate to F-6-P

33
Q

what regulates fructose-1,6-bisphosphate?

A

citrate and APT activate

F-2,6-bisphosphate and ADP inhibit

34
Q

what does G-6-phosphatase do? why is this enzyme necessary?

A

in gluconeogenesis
coverts G-6-P to glucose
necessary because hexokinase and glucokinase are not reversible

35
Q

what are the steps of the cori cycle? why is it necessary

A

lactate converted to glucose in the liver
glucose converted to lactate in muscle
necessary so that lactate is converted to glucose so the brain can use it

36
Q

where does glycerol come from?

A

the lipolysis of TG

37
Q

what are the energy requirements of gluconeogenesis from glycerol?

A

ATP

38
Q

what does pyruvate dehydrogenase (PDH) do?

A

usually converts pyruvate to Acetyl CoA but can also convert lactate to oxaloacetate

39
Q

what are the three enzymes that make up PDH?

A

pyruvate decarboxylase
dihydrolipyltransacetylase
dihydrolipoyl dehydrogenase

40
Q

what are the cofactors that PDH uses?

A 
NAD+
Thiamine pyrophosphate (TPP)
Lipoic acid
FAD
coenzyme A
41
Q

what is pyruvate decarboxylase part of and what does it do?

A

part of the enzyme pyruvate dehydrogenase
bound to TPP
pyruvate attaches to the TPP and is decarboxylated
hydroxyethyl group is transfered from the TPP on E1 to lipoic acid on E2

42
Q

what is dihydrolipoyl transacetylase and what does it do?

A

enzyme part of the pyruvate dehydrogenase enzyme

transfers acetyl group from the lipoic acid formed in step one to coenzyme A => acetyl CoA

43
Q

what is dehydrolipoyl dehydrogenase part of and what does it do?

A

part of pyruvate dehydrogenase enzyme
FAD binds to dehydrogenase
dehydrogenase oxidizes lipoic acid
reduces NAD+

44
Q

what regulates PDHC?

A

allosterically by kinase and certain substances
E1 is inhibited by protein kinase
- protein kinase is activated by ATP, Acetyl CoA and NADH
- protein kinase is inhibited by ADP and pyruvate
E1 activated by protein phosphatase
- protein phosphatase activated by Ca
E2 inhibited by allosteric binding of Acetyl CoA
E3 inhibited by allosteric binding of NADH

45
Q

what regulates protein kinase activity?

A

activated by ATP, acetyl CoA. and NADH

inhibited by ADP and pyruvate

46
Q

what regulates protein phosphatase activity?

A

Ca activates

biochem term 2 quiz 1 (5 decks)

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