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Cell Biology > Gluconeogenesis > Flashcards

Gluconeogenesis Flashcards

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1
Q

What is gluconeogenesis?

A

Making on new glucose

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2
Q

Which organs uses glucose as an energy source?

A

Brain, testes, erythrocytes and kidney medulla

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3
Q

Can glycosis and gluconeogenesis occur at the same time?

A

No, because its a futile cycle

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4
Q

When does glycosis takes place?

A

In the well fed state, 4-5 hours after a meal

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5
Q

When dos gluconeogenesis takes place?

A

After 4-5 hours in between meals

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6
Q

The brain can also get energy from another source

A

Ketone bodies, after 1-2 weeks without glucose so only under extreme conditions

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7
Q

What are the other ways in which the body can get glucose from?

A

Alpha keto acids, glycerol, lactate and pyruvate,

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8
Q

What is the first source of glucose in the body?

A

Liver, lasts 10- q8 hours in the absence of dietary intake of carbohydrates.

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9
Q

What is the second source of glucose?

A

Gluconeogenesis

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10
Q

Gluconeogenesis requires both mitochondrial enzymes and cytosolic enzymes

A

The first half occurs in the mitochondria while the second half occurs in the cytosol

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11
Q

How many enzymes are needed to bypass the 3 rate limiting steps?

A

4

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12
Q

Glycerol, lactate and the alpha keto acids are obtained from

A

Transamination of glucose amino acids.

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13
Q

The first irreversible step in GLYCOSIS is the

A

Phosphoenolpyruvate to pyruvate by pyruvate kinase

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14
Q

What is the enzyme that converts pyruvate to oxaloactate.

A

Pyruvate carboxykinase

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15
Q

Where is carboxylate found

A

Mitochondria

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16
Q

What is the cofactor in the carboxylation of pyruvate?

A

Biotin. Biotin is bound to apoenzyme of pyruvate carboxylase through an delta amino group of a lysylresidue to form biocytin

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17
Q

Can pyruvate come from alanine?

A

Yes

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18
Q

Oxaloactate can not leave the mitochondria so it must be converted to?

A

Malate by maleate dehydrogenase

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19
Q

In the cytosol malate is reoxidised to oxaloactate converted back to PEP by

A

Phosphoenolpyruvate carboxykinase

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20
Q

What is the first bypass state in gluconeogenesis ?

A

Carboxylation of pyruvate

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21
Q

OAA is converted to PEP by

A

Pep- carboxykinase using hydrolysis of GTP

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22
Q

PEP is converted to Fructose 1, 6 bisphosphate by

A

Glycolytic reactions that occur in the opposite direction in glycosis.

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23
Q

What is the allosteric regulator in decarboxylation reaction

A

Fructose 2,6 phosphate

24
Q

The enzyme fructose 1,6 bisphosphatase used in the conversation of ………………. Instead of the enzyme

A

Fructose 1,6 bisphosphate to fructose 6 phosphate instead of phosphofructokinase.

25
Q

How is gluconeogenesis regulated?

A

By energy levels of AMP in the cell, fructose 1,6 bisphosphatase is inhibited and regulator. By fructose 2,6 bisphosphate

26
Q

High levels of ATP is a signal of?

A

Energy poor state of the cell.

27
Q

Regulation of fructose 2,6 bisphosphate

A

Fructose 1,6 bisphosphatase is inhibited by fructose 2,6 bisphosphate.

28
Q

Where is the enzyme fructose 2,6 bisphosphate is found?

A

Liver

29
Q

When epinephrine or glycagon is secreted when happens?

A

cAMP is produced
cAMP dependent protein kinase is activated
This phospholates PFK2 and f2,6BPase activity
PFK2 is inhibited and F2,6BPase is activated
F2,6 breaks down and not inhibit F2,6 Bpass and glycosis is broken down

30
Q

In the absence of epinephrine or glycagon stimulation

A

cAMP is broken down
cAMP dependent protein kinase
PFK2 is activated and F2,6BPASE is inactivated
F2, 6 BP whose presence stimulates glycosis and inhibits gluconeogenesis .

31
Q

What happens when there are high levels of fructose 2,6 bisphosphate

A

Activate glycolysis

32
Q

Low levels of fructose 2,6 bisphosphate

A

Activation of gluconeogenesis

33
Q

What enzyme converts glucose 6 phosphate to glucose

A

Glucose 6 phosphase , found in the kidney and liver but not muscle like pyruvate carboxylate

34
Q

Can muscles produce glucose by gluconeogenesis

A

No

35
Q

What disease occurs when there is a deficiency of the enzyme glucose 6 phosphatase ?

A

glycogen storage disease type 1: Von gierke’ disease

36
Q

Type b glycogen 6 phosphate disease is named?

A

Glucose 6 phosphate translocation deficiency.

37
Q

Glycogen storage diseases

A

Inherited deficiency of glucose 6 phosphatase characterized by severe fasting hypoglycemia because glucose is unable tobe produced from eo ther gluconeogenesis or glycogenolysis

38
Q

Regulation of gluconeogenesis is determined by the

A

Circulation of glycagon, availability of gluconeogenesis substrates and allosteric activation by acetyl Co A.

39
Q

Activation by glycagon occurs in two ways

A

Changes in allosteric effectors ( lowers levels of fructose 2,6 bisphosphate)
Covalent modification of enzyme activity ( elevates cAMP levels)

40
Q

Gluconeogenesis rate is affected by availability of precursors especially

A

Glucose id amino acids

41
Q

Decrease insulin levels mobilize amino acids from muscles to provide

A

Carbon skeletons for gluconeogenesis

42
Q

What allosteric activates hepatic pyruvate carboxylate during starvation

A

acteyl CoA

43
Q

What are the sources of glucose

A

Alfa keto acids , lactate, glycerol found in adipose tissues .

44
Q

What enzyme metabolize glycerol in the liver?

A

Glycerol kinase , from glycerol to glycerol phosphate

45
Q

Glycerol phosphate is oxidized by glycerol phosphate dehydrogenase to

A

Dihydroxyacetone

46
Q

Cori cycle

A

The cycling of lactate and glucose between peripheral tissue and liver

47
Q

Deceive the cori cycle?

A

Blood borne glucose is converted by exercising muscles to lactate which diffuses in the blood. The liver takes up the lactate and reconverts it to glucose which is released into the normal circulation. Lactate dehydrogenase in the liver converts lactate to oxaloactate to PEP via gluconeogenesis .

48
Q

An increase in alanine in the muscle causes the release of alanine from muscle which will then go to

A

Into the liver and be converted glucose and then go to the muscle

49
Q

How many ATP are needed to synthesis one mole of glucose from pyruvate in gluconeogenesis ?

A

12 ATP

50
Q

In step 1 the glycolysis enzyme is ………. While the gluconeogenesis enzyme is

A

Hexokinase or glucokinase and glucose 6 phosphate

51
Q

Step 3.

A

Phosphofructokinase ………, fructose 1,6 bisphosphatase

52
Q

Step 9

A

Pyruvate kinase ……… Pyruvate carboxylase and PEPCk

53
Q

PC is activated by

A

Acetyl COA and ADP

54
Q

PEP ck synthesis is increased

A

Glycagon and ADP

55
Q

F 1,6 BPase is inhibited by

A

f2, 6 BP and AMP

56
Q

F 1,6 BPase

A

Citrate and glucagon

Cell Biology (13 decks)

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