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Blake_Biochemistry Test II > Blake_BIochem_25_Glycolysis and Gluconeogenesis > Flashcards

Blake_BIochem_25_Glycolysis and Gluconeogenesis Flashcards

1
Q

What are the irreversable steps in Glycolysis? (3)

  • Substrate to product/Enzyme
    • side rxns
A
  • Glucose ⇒ Glucose 6-phosphate/Hexokinase
    • ATP to ADP
  • Fructose 6-Phosphate ⇒Fructose 1,6-biphosphate/ Phosphofructokinase
    • ​ATP to ADP
  • Phosphoenolpyruvate ⇒Pyruvate/ Pyruvate kinase
    • ATP to ADP
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2
Q

Stage one of Glycolysis (3)

  • Substrate to product/Enzyme
A
  • Glucose⇒Glucose 6-phosphate/ Hexokinase
  • Glucose 6-phosphate ⇔ Fuctose 6-phosphate / Phosphoglucose Isomerase
  • Fructose 6-phosphate⇒Fructose 1,6-biphosphate/ Phosphofructokinase
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3
Q

Stage two Glycolysis (1)

  • Substrate to Products/ Enzyme
A
  • Fructose 1,6-biphosphate (splits)
    • ⇔ Glyceraldehyde 3-phosphate (GAP)/ Aldolase
    • ⇔Dihydroxyacetone phosphate/Aldolase
      • Dihydroxyacetone phosphate ⇔ Glyceraldehyde 3-phosphate (GAP)/triose phosphate isomerase

So there are 2 GAPs produced from 1 Glucose => phase 3 has twice the substrate

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4
Q

Stage Three of Glycolysis

  • Substrate to Products/ Enzyme
A
  • Glyceraldehyde 3-phosphate (GAP) ⇔ 1,3-biphosphoglycerate/ GAPDH (​Pi, NAD+ ⇔ NADH)
  • 1,3-Biphosphoglycerate ⇔ 3-Phosphoglycerate/ Phosphoglycerate kinase
  • 3-Phosphoglycerate ⇔ 2- Phosphoglycerate/ Phosphoglycerate mutase
  • 2- Phosphoglycerate ⇔ Phosphoenolpyruvate/ Enolase (​H2O released)
  • Phosphoenolpyruvate⇒ Pyruvate/ Pyruvate kinase (ATP to ADP)
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5
Q

Gluconeogenesis vs Glycolysis

Enzyme Glycolysis/bypass enzyme gluconeogenesis

A
  • Hexokinase (glucokinase) / Glucose 6-phosphatase
  • Phosphofructokinase -1/ fructose 1,6-biphosphatase
  • Pyruvate Kinase/ PEP carboxykinase
  • **/ pyruvate carboxylase
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6
Q

Which enzyme of Glycolosis is different in the Liver?

A

Hexokinase (other tissues); Glucokinase (in Liver)

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7
Q

How many ATP are used/produced in phase 1 of Glycolysis

A

No ATP produced

2 ATP consumed

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8
Q

What is the strategy of the initial steps of glycolysis? (2)

A
  1. Trap the glucose in the cell
  2. Form a compound that can be cleaved into 2, phosphorylated, three-carbon units
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9
Q

GAPDH stands for:

A

Glyceraldehyde 3-Phosphate Dehydrogenase

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10
Q

Where is GLUT1 used for glucose uptake?

A

Ubiquitously, but high in RBCs adn brain

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11
Q

Where is GLUT2 used for Glucose Uptake?

A

Main transporter in the Liver

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12
Q

Where is GLUT3 used for glucose uptake?

A

Neurons

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13
Q

Where is GLUT4 used for glucose uptake?

A

Skeletal muscle, heart, adipose tissue (insulin dependent)

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14
Q

Summarize Phase 1 Glycolysis:

A

trapping and preparation

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15
Q

Summarize Phase 2 Glycolysis:

A

Cleavage and isomerization

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16
Q

Sumarize Phase 3 Glycolysis:

A

3 steps: producing x2 Pyruvate

  • GAPDH
  • Phosphoglycerate kinase/mutase
  • Enolase/pyruvate kinase
17
Q

What is the rate-limitting step in Glycolysis?

A

Phosphoenolpyruvate to Pyruvate

18
Q

What are the different fates of pyruvate depending on the presence or absence of O2?

A

with O2: Aerobic respiration; Pyruvate to TCA cycle

without O2: Anaerobic respiration; Pyruvate reduced to Lactate

19
Q

In what tissues is glycolysis regulated:

A
  • In muscle - to meet need for ATP during Exercise
  • In Liver - in response to biochemical diversity and need
20
Q

How is Glycolysis regulated in muscle tissues during rest?

What about Glycogen?

A
  • Hexokinase is inhibited by Glucose 6-phosphate
  • Phosphofructokinase (PFK) and Pyruvate Kinase are inhibited by ATP
  • Glucose 6-phosphate is converted to glycogen
21
Q

How is glycolysis regulated in muscle tissues during exercise?

What about Glycogen?

A
  • PFK is stimulated by low energy AMP
  • Fructose 1,6 biphosphate feedforward stimulation of Pyruvate kinase
  • Glycogen is converted to Glucose 6-phosphate
22
Q

How is glycolysis regulated in the liver?

A
  • Phosphofuctokinase (PFK)
    • Activated by Fructose-2,6-BP
    • Inhibited by citrate
  • Glucokinase is NOT inhibted by glucose 6-phosphate (like hexokinase in other tissues) therefore, glucose is permanently trapped
  • Pyruvate kinase is regulated by allosteric effectors and covalent modification
23
Q

How does [Insulin] and [Glucagon] affect Phosphofructokinase (PFK) in the liver?

A
  • High Insulin/low glucagon: stimulates protein phosphatases which stimulates PFK-2 to produce Fructose 2,6BP which stimulates PFK-1
  • Low insulin/high glucagon increases [cAMP] which stimulates Protein kinase A which stimulates PFK-2 to produce Fructose 6-P
24
Q

How does [Insulin] and [Glucagon] affect Pyruvate Kinase (PK) in the liver?

A
  • high insulin/low glucagon: stimulates protein phosphatases which stimulates PK
  • low insulin/high glucagon: increases [cAMP] which stimulates protein kinase A which inhibits PK
25
Q

how is Glucokinase regulated by blood glucose?

A

low blood glucose = inhibition - don’t want to trap glucose

26
Q

What is the fate of pyruvate under Aerobic Fasting conditions?

A

Gluconeogenesis

27
Q

daily glucose requirement for the brain?

for the whole body?

glucose in body fluids?

Glucose available from glycogen?

A

120g

160g

20g

190g

28
Q

Substrates in order for Gluconeogenesis:

A
  • Pyruvate
  • Oxaloacetate
  • phosphoenolpyruvate
  • 2-phosphoglycerate
  • 3-phosphoglycerate
  • 1,3-biphosphoglycerate
  • GAP/Dihydroxyacetone phosphate
  • Fructose 1,6,-biphosphate
  • Fructose 6-phosphate
  • Glucose 6-phosphate
  • Glucose

Blake_Biochemistry Test II (11 decks)

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