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BioChem Exam 4 > Lecture 26: Glucose Catabolism (Glycolysis) > Flashcards

Lecture 26: Glucose Catabolism (Glycolysis) Flashcards

1
Q

Overview of Glycolysis

Where does glycolysis happen?

A

Within the cytosol of cells

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2
Q

Overview of Glycolysis

What is glucose converted into?

A

pyruvate

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3
Q

Overview of Glycolysis

How is energy captured? What does it synthesize?

A

ATP and NADH

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4
Q

Overview of Glycolysis

What are the two phases of glycolysis?

A

Preparatory phase
Payoff Phase

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5
Q

Overview of Glycolysis

What happens in the preparatory phase?

A

1 molecule of glucose is converted into 2 molecules of glyceraldehyde 3-phosphate
* 2 ATP are consumed

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6
Q

Overview of Glycolysis

What happens in the payoff phase?

A

2 molecules of glyceraldehyde 3-phosphate are converted into 2 molecules of pyruvate
* 4 ATP and 2 NADH are produced

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7
Q

Overview of Glycolysis

What is the net production from 1 molecule of glucose?

A

1 pyruvate
2 ATP
2 NADH

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8
Q

Overview of Glycolysis

How many steps are in gycolysis?

A

10

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9
Q

Preparatory Phase

What two products are glucose broken down into?

A

glyceraldehyde 3-phosphate (moves to payoff phase)
Dihydroxyacetone phosphate (must be converted)

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10
Q

Preparatory Phase

What is step 1?

A

Phosphorylation of Glucose:
Glucose enters into glycolysis by conversion to glucose 6-phosphate using enam hexokinase (prevents glucose from exiting the cytosol, makes the reaction irreversible and spontaneous), regulated by product inhibition

uses 1 ATP

there are regulation sites at irreversible site

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11
Q

Preparatory Phase

What is Step 3?

A

2nd Priming Phosphorylation:
addition of phosphate onto the C1 position using phosphofructokinase (PFK) to activate, used to further activate the 6-carbon unit
spontaneous, irreversible

Uses 1 ATP

Phosphofructokinase is key enzyme that regulates the pace of glycolysis

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11
Q

Preparatory Phase

What is step 2?

A

Phosphohexose Isomerization:
catalized by phosphohexose isomerase
converts glucose into fructose (from aldose to ketose) as it is easier to add phosphates to the C1 position and allows for symetrical cleave
reversible

product concentration kept low to drive forward

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11
Q

Preparatory Phase

What is step 5?

A

Triose Phosphate Interconversion:
enam Triose phosphate isomerase converts the DHAP to GAP to continue forward.
reversible

GAP concentration kept low to pull reaction forward

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11
Q

Preparatory Phase

What is step 4?

A

Aldol cleavage of F-1,6-bP:
Using the enam Aldolase, it cuts the carbon into Glyceraldehyse 3-phospahte (GAP) and dihydroxyacetone (DHAP)
reversible

GAP concentration kept low to pull reaction forward

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12
Q

Payoff Phase

What is step 6?

A

Oxidation of GAP:
enam Glyceraldehyde 3-phosphate dehydrogenase is used to oxydize aldehyde group into a carboxyl group.
produced energy and stores in carboxyl group
NAD+ is a cofactor and is reduced to NADH
reversible

coupled to next reaction to pull forward

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13
Q

Payoff Phase

What is step 7?

A

1st production of ATP:
high evergy phosphate donated to ADP to create ATP (substrate-level phosphorylation)
Phosphogycerate kinase catalyzes
reversible, catalyzes both directions

14
Q

Payoff Phase

What is Step 8?

A

Migration of the Phosphate:
Phosphoglycerate Mutase catalyzes the migration of the functional group (phosphate shifts from C3 to C2)
reversible

reactact concentration kept high by PGK to push forward

15
Q

Payoff Phase

What is step 9?

A

Dehydration of 2-PG to PEP:
enolase dehydrates 2-phosphoglycerate (2-PG) to form Phosphoenolpyruvate (PEP), high evergy phosphate
slightly reverisble

product concentration kept low to pull reaction forward

16
Q

Payoff Phase

What is step 10?

A

2nd Production of ATP:
substrate-level phosphorylation
pyruvate kinase transfer the phosphate to ADP and leaves pyruvate
the enam requires a cofactor of divalent metals (Mg++ or Mn++)
irreversible/spontaneos

17
Q

Fates of Pyruvate

What is pyruvate used for?

A

Creation of:
Ethanol (used for fermentation)
Lactate (used for fermentation)
Acetyl CoA (used for Citric Acid cycle)

18
Q

Regulation of Glycolysis

What 3 enzymes catalyze and regulate the spontaneous reactions of glycolysis?

A

Hexokinase: inhibited by product glucose-6-phosphate
Phosphofructokinase: rate limiting step, more ATP and pH decrease limits PFK activity
Pyruvate kinase: last step in glycolysis, ATP allosterically inhibits pyruvate kinase, fructose 1,6 biphosphate activates it

19
Q

Summary of Glycolysis

What is the Equation for Glycolysis

A

Glucose + NAD + 2 ADP + 2 Pi -> 2 Pyruvate + 2 NADH + 2 H + 2 ATP

BioChem Exam 4 (8 decks)

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