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601 - exam 1 > 2.4 Gluconeogenesis > Flashcards

2.4 Gluconeogenesis Flashcards

1
Q

What depends on glucose as their primary fuel and what relies on glucose as their only fuel?

A

Brain

RBCs

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2
Q

Glycolysis, gluconeogenesis and glycogenolysis are regulated by

A

Insulin and glucagon

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3
Q

What happens after a meal?

A

High blood glucose signals the pancreas to release insulin
(Tells muscles and adipose tissue to take up glucose)

Glycolysis and glycogenesis

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4
Q

What happens during fasting?

A

Low blood glucose levels tells the pancreas to release glucagon

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5
Q

What 2 major metabolic pathways function in the liver to maintain blood glucose levels at a steady state in order to feed the brain and RBCs?

A

Glycogenolysis and gluconeogenesis

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6
Q

Define glycogenolysis

A

Breakdown of glycogen

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7
Q

Define gluconeogenesis

A

Synthesis of glucose from non-carbohydrate precursors

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8
Q

Describe a short fast

A

Utilizes glucose and breakdowns glycogens

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9
Q

Describe overnight fast

A

Glycogen breakdown and gluconeogenesis

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10
Q

Describe prolonged fast

A
  • Breakdown of last remaining glycogen in the liver
  • Gluconeogenesis becomes the sole source of glucose
  • Lipolysis generates ketones for additional fuel
  • Muscle protein is degraded for AA
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11
Q

Major site of gluconeogenesis to supply blood glucose is the ___

A

liver

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12
Q

What are the major precursors for gluconeogenesis?

A

Lactate
Glycerol
AA
TCA cycle intermediates

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13
Q

Define glucogenic

A

Noncarbohydrate carbon substances that can be converted to pyruvate

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14
Q

Examples of glucogenic

A

Lactate and alanine

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15
Q

Catabolic rxns of fatty acids break off 2 carbon atoms at a time as acetyl-CoA which ___ be converted to glucose

A

Can’t

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16
Q

An even number of fatty acids produces ___

A

Acetyl-CoA

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17
Q

An odd number of fatty acids produces ___

A

Succinyl-CoA

FA off –> acetyl-CoA + single propionyl-CoA –> methylmalonyl-CoA –> succinyl-CoA

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18
Q

Glycerol is ___

A

Glucogenic

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19
Q

Gluconeogenesis is the reversal of glycolysis with 3 enzymatic exceptions:

A
  • Conversion of pyruvate to PEP
  • Conversion of F 1,6-biphosphate to F6P
  • Conversion of G6P to Glucose
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20
Q

How does gluconeogenesis start?

A

With the transport of pyruvate to the mitochondria and then its conversion to PEP

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21
Q

What enzymes does pyruvate need to convert to PEP?

A

Pyruvate carboxylase
MT malate dehydrogenase
Cytosolic malate dehydrogenase
PEP carboxykinase

22
Q

What are the 2 different pathways for conversion of pyruvate to PEP?

A

Pyruvate (enters mitochondria) to oxaloacetate to malate (then leaves mitochondria) to oxaloacetate to PEP

Lactate to pyruvate (enters mitochondria) to oxaloacetate to PEP

23
Q

What does oxaloacetate convert into since it can’t directly cross the mitochondrial membrane?

A

Malate

24
Q

The choice between the 2 pathways for conversion of pyruvate to PEP depends on

A

Cytostolic NADH

25
Q

Conversion of Oxaloacetate to malate and malate to oxaloacetate yields what

A

NADH each

26
Q

Pyruvate to PEP conversion is regulated by what 2 different mechanisms?

A

PEP carboxykinase

Pyruvate carboxylase

27
Q

PEP carboxykinase expression is induced by ___ and inhibited by ___

A

Glucagon

Insulin

28
Q

Pyruvate carboxylase is ___ regulated by ___

A

Positively

Acetyl-CoA

29
Q

Once PEP is made and conditions favor gluconeogenesis, the enzymes of glycolysis can run in the opposite direction as far as

A

fructose-1,6-bisphosphate

30
Q

Fructose-1,6-bisphosphatase converts fructose-1,6-bisphosphate to

A

fructose 6-phosphate

31
Q

Fructose-2,6-bisphosphate is a ___ regulator

A

Allosteric

32
Q

Allosteric effectors of fructose-1,6-bisphosphatase are also allosteric effectors of

A

phosphofructokinase

33
Q

Interconversion of F6P to F-1,6-bisphosphate is regulated by __ via the production of ___

A

Insulin and glucagon

Fructose-2,6-bisphosphate

34
Q

Glucose-6-phosphatase dephosphorylates ___ to ___

A

G6P

Glucose

35
Q

___ is an integral membrane protein of the ER

A

Glucose-6-phosphatase

36
Q

Steps for glucose-6-P converting to glucose

A
  1. Glucose-6-P is transported to ER lumen by a specific transporter
  2. Glucose-6-P is hydrolyzed by glucose-6-phosphatase
  3. Glucose is transported to cytosol via transporter T2
  4. Transported out of cell via GLUT2
37
Q

Glucose is transported out of liver cells by

A

GLUT2

38
Q

A high AMP indicates that the energy charge is low and signals the need for ATP. This results in

A

glycolysis stimulation

39
Q

High ATP and citrate indicates that the energy charge is high and intermediates are abundant. This results in

A

Glycolysis inhibition

40
Q

___ is regulated indirectly by glucagon via ___

A

Pyruvate kinase

Protein Kinase A (PKA)

41
Q

Gluconeogenesis requires the input of ___ equivalents of ATP/GTP for each molecule of glucose

A

6

2 ATP needed by pyruvate carboxylase
(2 GTP needed by PEP carboxykinase)
(2 ATP needed by phosphoglycerate kinase)

42
Q

Gluconeogenesis requires how many NADH?

A

2

43
Q

Describe the cori cycle (lactic acid cycle)

A
  • During high muscle activity the rate of glycolysis is faster than the rate of TCA cycle, so causes pyruvate to be converted to lactate
  • Lactate is sent to bloodstream and is used by liver as a gluconeogenic substrate
44
Q

Describe the alanine cycle (Cahill cycle)

A
  • shuttles amino acid groups from the muscle to the liver for disposal as urea
  • Pyruvate from glycolysis is converted to alanine by alanine transaminase which is taken to liver where nitrogen enters the urea cycle and pyruvate undergoes gluconeogenesis
45
Q

The liver inhibits and stimulates what

A

Inhibits gluconeogenesis

Stimulates lipogenesis and glycogen synthesis

46
Q

Adipose tissue stimulate and inhibits what

A

Stimulates glucose uptake and lipogenesis

Inhibits lipolysis

47
Q

Striated muscle stimulates what

A

Glucose uptake, glycogen synthesis and protein synthesis

48
Q

Describe type I diabetes

A

Glucose stays in the blood because of the lack of insulin
Insulin isn’t released from pancreas
Hyperglycemia
Beta-cells are destroyed

49
Q

Describe type II diabetes

A

Pancreas releases insulin

Glucose remains in blood b/c tissues fail to respond to insulin

50
Q

Describe healthy glucose metabolism

A

Insulin is released by pancreas
Glucose is removed by blood
Insulin binds to insulin receptors

601 - exam 1 (10 decks)

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