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Biochemistry > Unit 4: Chapter 17, Gluconeogenesis > Flashcards

Unit 4: Chapter 17, Gluconeogenesis Flashcards

1
Q

Gluconeogenesis

A

Synthesis of glucose from pyruvate and related 3 and 4 carbon compounds (lactate, amino acids, and glycerol)

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2
Q

Major sites of gluconeogenesis

A

Liver and kidney

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3
Q

Reactions of glucogenesis of enzymes occur

A

cytoplasm, mitochondria, ER by enzymes

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4
Q

During fasting or starvation ____ is important and why

A

gluconeogenesis since glucose is primary fuel for brain and only fuel for red blood cells

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5
Q

gluconeogenesis converts ____ into each glucose

A

2 pyruvates

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6
Q

Pruvate is formed from

A

lacid acid fermentation: muscle derived lactate in the liver by lactate dehydrogenase

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7
Q

Carbon skeletons of some _____ can be converted into gluconeogenesis intermediates

A

amino acids

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8
Q

___ is derived fom hydrolysis of triaglycerols which cna be converted into dihydroxyacetorne phosphate to be processed by glucogenesis or glycolysis

A

Glycerol

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9
Q

What molecules can go through gluconeogenesis

A

LActate, amino acids, and glycerol

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10
Q

Why is gluconeogenesis is not complete reversal of glycolysis?

A

Due to the 3 irreversible steps in glycolysis
Step 1: hexokinase
Step 3: phosphofructokinase (PFK)
Step 10: Pyruvate kinase

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11
Q

To reverse irreversible steps of glycolysis, reactions must turn

A

endergonic

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12
Q

Why is gluconeogensis expensive process?

A

Have to spend ATP and GTP since reaction is anabolic and endergonic

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13
Q

Hexokinase will be reversed by and where is location

A

G6Phosphatase (G6Pase) and occurs in ER

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14
Q

Phosphofructokinase will be reversed by and where is location

A

F 1,6 biphosphatase (F1, 6BPase) and occurs in cytosol

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15
Q

Pyruvate kinase will be reversed by

A

Pyruvate Carboxylase which occurs in mitochondria and PEP Carboxykinase which occurs in cytoplasm

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16
Q

Formation of _____ requires 2 enzymes of pyruvate carboxylase and PEP carboxykinase

A

phosphoneol (PEP) pyruvate
Step 10

17
Q

Conversion of step 10 begins with formation of ______

A

oxaloacetate

18
Q

What is reaction equation of formation oxaloacetate?

A

pyruvate + CO2 + ATP + H20 –> oxaloacetate + ADP + Pi + 2H+

19
Q

Formation of oxaloacetate occurs in

A

mitochondria

20
Q

Formation of oxaloaetate occurs in 3 stages by

A

pruvate carboxylase

21
Q

Pyruvate carboxylase requires what

A

Vitamin biotin as cofactor

22
Q

The molecule of ATP invested to form oxaloacetate to bypass step 10 is used to power

A

addition of CO2 to pyruvate
(carboxylation)

23
Q

Oxaloactetate is reduced to ______

A

maltate

24
Q

Why is oxaloacetate reduced to maltate?

A
  • Maltate can be transported into the cytoplasm where it is reoxidized to oxaloacetate with generation of cytoplasmic NADH
  • Oxaloacetate cannot simply just cross the mitcondria and go to cytoplasm since mitochondrial membrane does not have a transporter for oxaloacetate
25
Q

Oxaloacetate create phosphoneol (PEP) pyruvate in cytosol by

A

Phosphoenolpyruvate (PEP) carboxykinase

26
Q

When oxaloacetate becomes Phosphoneol pyruvate what occurs?

A
  • CO2 that was added to pyruvate by pyruvate carboxylase comes off in this step (Decarboxylation)
  • Decarboxylation makes reaction exergonic
27
Q

What enzyme is involved in electron carriers such as NAD+/NADH and FADH/FADH2?

A

Dehydrogenase (substrate + dehydrogenase)

28
Q

What is reaction equation for formation of PEP pyruvate from oxaloacetate

A

Oxaloacetate + GTP –> PEP pyruvate + GDP + CO2

29
Q

Sume of reactions in step 10 of gluconeogenesis

A

pyruvate + ATP + GTP + H20 –> Phosphoenol (PEP) pyruvate + ADP + GDP + Pi + 2 H+

30
Q

Phosphatase

A

catalyzes reactions which removes phosphates

31
Q

Reactions of step 3 of gluconeogenesis

A

Fructose 1,6 biphosphate + H20 –> Fructose 6 Phosphate + Pi

32
Q

Which step of gluconeogenesis if generation of free glucose?

A

Step 1

33
Q

Why is the generation of free gluocse important?

A

Important control point

34
Q

What ocurs in final step of gluconeogenesis?

A
  • Occurs only in liver
  • Glucose 6 phosphate is transported into the lumen of ER
  • catalyzed by glucose 6 phosphatase
35
Q

How many high transfer potential phosphoryl groups are spent in gluconeogenesis?

A

6

36
Q

Overall reaction for gluconeogenesis

A

2 pyruvate + 4 ATP + 2 GTP + 2 NADH + 2 H+ and 6 H20 –> glucose + 4ADP + 2 GDP + 6Pi + 2NAD+

37
Q

Is gluconeogensis exergonic or endergonic?

A

Exergonic

38
Q

Gluconeogensis and glycolysis are ____ reaction

A

Futile

39
Q

Futile reaction

A

occurs when two metabolic pathways run simultaneously in opposite directions and have no overall effect other than to burn ATP/GTP and heat produced

Biochemistry (17 decks)

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