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Biochem > Lecture 21: Gluconeogenesis > Flashcards

Lecture 21: Gluconeogenesis Flashcards

1
Q

Role of Liver as energy provider

A

-maintain blood glucose by glycogen breakdown and gluconeogenesis
-produce ketone bodies in ketogenesis

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2
Q

*Carbon sources of gluconeogenesis

A

-lactate
-amino acids
-glycerol
-fructose

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3
Q

Energy source of gluconeogenesis

A

ATP from FATTY acid OXIDATION

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4
Q

*Rate-limiting step of gluconeogenesis

A

-step catalyzed by pep carboxykinase

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5
Q

Gluconeogenesis

A

-liver producing glucose
-many enzymes reused except irreversible steps

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6
Q

Gluconeogenesis reaction

A

lactate to pyruvate to oxaloacetate (occurs in TCA cycle) to phosphoenolpyruvate

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7
Q

Oxaloacetate in gluconeogensis

A

-comes from TCA cycle
-transported from mitochondria via aspartate/malate shuttle

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8
Q

*Futile cycle regulation glycolysis vs gluconeogenesis

A

-G6Pase expressed ONLY in liver
-6-phosphofructokinase and pyruvate kinase regulated ALLOSTERICALLY

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9
Q

Glucose to pyruvate ATP

A

-YIELDs 7 ATP

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10
Q

Pyruvate to glucose ATP

A

-NEEDS 11 ATP

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11
Q

Glucokinase

A

-replaces hexokinase in the liver
-uses glucose only when there is a LOT
-futile system with G6Pase keeps blood sugar up

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12
Q

Activation of Gluconeogenesis

A

-inhibition of glycolysis
-fatty acid oxidation
-increase in citrate

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13
Q

Inhibition of glycolysis

A

ATP inhbits 6phosphofructokinase and pyruvate kinase

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14
Q

Fatty Acid oxidation

A

-supplies ATP for gluconeogenesis
-increase acetyl CoA that INactivates pyruvate DEHYDrogenase and ACTIVATES pyruvate CARBoxylase

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15
Q

Increase in citrate

A

-caused by increase in oxaloacetate and acetyl CoA
-negative allosteric regulator of 6phosphofuctokinase

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16
Q

CHART SLIDE 9

A

LIKE ACTUALLY LOOK

17
Q

Alcohol and gluconeogenesis

A

-oxidation of ethanol by liver depletes NAD+
-excess NADH converts pyruvate to lactate
-gluconeogenesis by liver is suppressed

18
Q

Problems of alcohol

A

-hypoglycemia
-lactic acidosis
-problem more severe when glycogen storage in liver is depleted (malnutrition/exercise)

19
Q

Pentose Phosphate Pathway

A

-produces NADPH
-produces ribose-5-phosphate used for DNA synthesis

20
Q

Pentose Pathway rate-limiting AND commintment step

A

-first step

21
Q

G6P fate

A

-glycolysis
-glycogen synthesis
-PPP
-glucose production in liver

22
Q

NADH sources

A

-glycolysis
-TCA
-fatty acid oxidation

23
Q

NADH uses

A

-generation of ATP by oxidative phosphorylation

24
Q

NADPH sources

A

-PPP

25
Q

NADPH uses

A

-anabolic reactions

26
Q

Ketone bodies

A

-water soluble products of lipid oxidation (acetyl CoA)
-produced by liver during fasting
-reduces need for gluconeogenesis
-reduces protein wasting
-used by brain and skeletal muscles as fuel

27
Q

Ketone body synthesis

A

-mitochondria
-HMG-CoA synthase expressed at high levels during fasting

  1. 2 acetyl CoA (C2) –> acetoacetyl CoA
  2. Acetoacetyl CoA + acetyl CoA –HMGsynthase–> HMG-CoA (C6)
28
Q

ratio of acetoacetic acid to B-hydroxybutyric acid

A

-dependent on ration of NAD+/NADH in liver mitochondria

29
Q

ketoacidosis

A

-high concentration of ketone bodies
-leads to spontaneous production of acetone from acetoacetic acid

30
Q

Using ketone bodies

A

-converted to acetyl CoA in mitochondria outside liver
-reducing equivalent in B-hydroxybutyric acid harvested as NADH
-acetyl CoA used as fuel in TCA cycle

31
Q

B-hydroxybutyric acid to acetyl-CoA

A

-to acetoacetic acid first
-then to acetoacetyl CoA
= 2 acetyl CoA

32
Q

Energy sources for physical activities

A

-fatty acid and ketone bodies are preferred to glucose when O2 is sufficient

33
Q

Fatty Acid oxidation increases Citrate

A

-suppresses glycolysis
-similar to switching between glycolysis and gluconeogenesis

34
Q

Slide 18

A

come on u got this king

35
Q

Ketoacidosis

A

-mostly in type I diabetics
-low insulin promots lipolysis in adipose tissue
-production of lots of ketone bodies LOWERS blood pH
-medical emergency

36
Q

When the blood glucose levels are low, which of the following reactions is suppressed in the liver?

-Conversion of fatty acids to acetyl CoA
-Conversion of pyruvate to acetyl CoA
-Conversion of pyruvate to oxaloacetate
-Conversion of oxaloacetate to phosphoenolpyruvate
-Conversion of lactate to pyruvate

A

Conversion of pyruvate to acetyl CoA

Biochem (30 decks)

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