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BCH 369 > Week 8: Glycolysis, Gluconeogensis, and Pyruvate Dehydrogenase Complex > Flashcards

Week 8: Glycolysis, Gluconeogensis, and Pyruvate Dehydrogenase Complex Flashcards

1
Q

What sign is an irreversible reaction

A

Negative Delta G
Spontaneous

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2
Q

How long does gene level control enzymes take

A

Hours

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3
Q

How long does covalent modification (Phosphorylation, Methylation)

A

In seconds

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4
Q

How long does Allosteric Regulation

A

Milliseconds

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5
Q

3 Enzymes that are control enzymes in glycolysis

A

Step 1 - Hexokinase, add P to #6C on glucose
Step 3 - Phosphofructokinase, add 2nd P to F-1,6
Step 9 - Pyruvate Kinase, add P to ADP from Phosphoenolpyruvate

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6
Q

What is the committed step in glycolysis

A

PFK

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7
Q

Muscle Mechanisms

A

Energy

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8
Q

Liver Mechanisms

A

Energy and biosynthesis
From amino acids and fatty acids

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9
Q

Muscle process in glycolysis is due to what ratio

A

Regulation of glycolysis in muscle is mostly due to energy charge = ATP/AMP

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10
Q

What is ATP to PFK and Pyruvate Kinase

A

It is a negative effector

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11
Q

What is the key regulator of glycolysis in mammals

A

PFK

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12
Q

What does ATP and AMP to cells

A

Allosterically inhibited by ATP and Allosterically stimulated by AMP

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13
Q

How is the entire pathway regulated

A

1.) Energy Charge
2.) Feedback

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14
Q

When ATP needs are great how does the body compensate

A

Adenylate Cyclase generates ATP from 2ADP

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15
Q

Liver: Key regulators

A

Key Regulators are
Citrate (reports on status of CAC)
Fructose 2,6-Bisphopahte

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16
Q

What does citrate and F-2,6-BP due to PFK

A

Citrate inhibits PFK
F-2,6-BP activates PFK

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17
Q

What does high citrate concentration due

A

Plenty of biomaterial to work with, high citrate then slows down glycolysis because less glucose is needed

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18
Q

Name two Bifunctional Enzyme

A

PFK-Kinase
FBP-Phosphatase

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19
Q

What kind of enzyme is hexokinase

A

Allosteric

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20
Q

How is Pyruvate Kinase regulated in liver as in muscle

A

Allosterically

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21
Q

In liver how is Pyruvate Kinase also regulated

A

Covalent Modification

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22
Q

What does low blood glucose lead to

A

Phosphorylation and inhibition of liver pyruvate kinase

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23
Q

Glucagon

A

Hormone that stats phosphorylation cascade that ends up phosphorylating pyruvate kinase

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24
Q

How many steps in Gluconeogensis

A

Pyruvate - Glucose in 11 steps
7 of them are the same as in glycolysis

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25
Q

Where does Gluconeogensis happen

A

Major site in liver, but can also happen in the kidney

26
Q

When is Gluconeogensis important

A

Important during tasting or starvation - glucose is primary fuel for the brain and only fuel for red blood cells

27
Q

How can pyruvate be from in the liver

A

Can be formed from lactate in the liver by lactate dehydrogenase. Then pyruvate can make glucose

28
Q

What can Carbon skeltons be converted to

A

Carbon skeleton of amino acids can be converted to gluconeogenic intermediates

29
Q

How is glycerol derived

A

Gylcerol, derived from hydrolysis of triacylglycerols, can be converted to dihydroxyaceton phosphate, which can be used in both glycolysis and gluconeogensis

30
Q

Step 1 of Gluconeogensis

A

Step 1 - Pyruvate Carboxylase Reaction
Requires pyruvate carboxylase (in mitochondria) and PEP carboxykinase (cytoplasm)
Pyruvate - Oxaloacetate occurs in 3 steps
Requires biotin as a cofactor carries carboxylate groups (COO)

31
Q

Step 2 - Phosphoenolpyruvate Carboxykinase

A

Oxaloacetate moved to cytoplasm before this step

32
Q

Step 9 - Fructose-1,6-Bisphosphatase

A

Takes off phosphate
Allosteric enzyme is the control point

33
Q

Step 11 - Glucose 6-Phosphate

A

Glucose 6-Phosphate transported to the ER
Glucose 6-Phosphatase, Integral membrane enzyme on surface of ER, catalyzes Glucose 6-P to Glucose

34
Q

What remains the same from glycolysis to gluconeogensis

A

Steps 3-8
Step 10: Isomerase

35
Q

Why don’t glycolysis and gluconeogensis run in reverse

A

Both glycolysis and gluconeogensis have control points with different ezymes, that are unidirectional (irreversible)

Steps 1,3,9 - Regulatory steps in glycolysis
Steps 1,2,9,11 - Regulatory steps in gluconeogensis

36
Q

What are the key regulator of glucose metabolism

A

Fructose-2,6-Bisphosphate stimulates glycolysis and inhibits gluconeogensis

37
Q

What is F-2,6-BP synthesized by and hydrolyzed by

A

Phosphofructokinase 2 (PFK 2)
Fructose Bisphoshatase 2

38
Q

Are they on the same peptide chain

A

Yes, bifunctional enzyme

39
Q

What is released when blood glucose levels are low

A

The hormonne glucagon is secreted by the pancreas

40
Q

What does the glucagon pathway lead to and what does it inhibit and stimulate

A

Leads to phosphorylation of the bifunctional enzyme
Inhibits kinase
Stimulates phosphatase

41
Q

Pyruvate Dehydrogenase

A

Critical link between glycolysis and citric acid cycle

42
Q

What does the synthesis of Acetyl CoA from pyruvate require

A

Requires 3 enzymes and 5 coenzymes
(All the pyruvate dehydrogenase complex)

43
Q

The 3 steps in Pyruvate Dehydrogenase Complex

A

Decarboxylation
Oxidation
Transfer to CoA

44
Q

The 3 enzymes in pyruvate dehydrogenase complex

A

E1: TPP
E2: Lipoamide
E3: FAD

45
Q

E1-TPP
Enzyme
Reaction Catalyzed

A

Pyruvate Dehydrogenase Component
Oxidative decarboxylation of pyruvate

46
Q

E2-Lipoamide
Enzyme
Reaction Catalyzed

A

Dihydrolipoyl Transacetylase
Transfer of Acetyl group to CoA

47
Q

E3-FAD
Enzyme
Reaction Catalyzed

A

Dihydrolipoyl Dehydrogenase
Regeneration of the oxidized form of lipoamide

48
Q

How can lipoamide move between different active sites

A

Flexible linkages
“Swinging arm”

49
Q

How many enzymes are structurally integrates, and what enzyme does move

A

3 enzymes
Lipoamide arm allows rapid movement of substrates and products from one active site of the complex to another

50
Q

Steps of Complex Action

A
  1. Binding to TPP cofactor
  2. E2 inserts lipoamide into E1
  3. Transfer of acetyl group onto lipoamide goes to E2 active site
  4. Transfer of acetly group to CoA
  5. Lipoamide is oxidized by FAD
  6. FAD is oxidized by NAD+
51
Q

Is the formation of Acetyl CoA from pyruvate reversible or irreversible

A

Irreversible

52
Q

Where does Acetyl CoA go

A

Either Citric Acid Cycle or incorporation into fatty acid

53
Q

Out of the 3 E enzymes what is the key site of regulation

A

E1
Covalent modification

54
Q

What activates E1 enzyme

A

Phosphatase attached that removes the phosphate and thus activates the enzyme

55
Q

Is E1 allosteric

A

Yes

56
Q

What inhibits E1 comples

A

ATP
Acetyl CoA
NADH

57
Q

What stimulates the complex

A

ADP
Pyruvate

58
Q

Is a single large complex an advantage

A

Yes

59
Q

How is reaction facilitated

A

Facilitated by having active sites in close proximity

60
Q

When do reactants leave enzyme

A

Not until final product is made
limits side reaction
A more tightly controlled enzymatic mechanism

61
Q

What do all enzymes need to do

A

Need to exist in the proper amount because the entire thing is made together

62
Q

How is regulation efficient

A

Regulation is more effecient because regulatory enzymes are also a part of the complex

BCH 369 (10 decks)

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