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Enzymes of Glycolysis and TCA
all *enzymes from Bioenergetics III and IV
28
Medical
Graduate
09/08/2009

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Term
Hexokinase
Definition

1. First priming rxn

2. Adds a P to Glc from ATP to C6

3. Large -ΔG, drives forward rxn

4. Excess energy is released as heat

5. Keeps Glucose in the cell

Term

Phosphofructokinase-1

(PFK-1)

Definition

1. Commited step

2. 3rd step, 2nd priming step

3. Large -ΔG,(irreversible)

4. Major point of regulation

5. Adds second P from ATP to

Fru 6-P --> Fru 1,6-bisphosphate

Term
Aldolase
Definition

1. Cleaves Fru 1,6-phos--> 2 triose

2. pos ΔG, reversible rxn

3. Forward rxn is dirven by removal of products

Term

Glyceraldehyde 3-Phosphate Dehydrogenase

(GAPDH)

Definition

1. Adds Pi to glyeraldehyde 3-P

2. Produces NADH

3. Forms first high energy phosphate compound

(1,3-bisphosphoglycerate)

Term
Phosphoglycerate Kinase
Definition

1. Forms ATP

2. Converts 1,3 Bisphosphoglycerate --> 3-phosphoglycerate

3. -ΔG

Term
Enolase
Definition

1. Makes the 2nd high energy compound

2. Pos ΔG, reversible

3. Removal of water

4. 3-phosphoglycerate --> PEP

Term
Pyruvate Kinase
Definition

1. Makes ATP

2. PEP-->Pyruvate

3. Large -ΔG, irreversible

Term
NET RXN of Glycolysis
Definition

Glucose, 2ADP, 2P, 2 NAD+

--->

2Pyruvate 2ATP 2H+ 2NADH 2H20

Term
Regeneration of NAD+
Definition

1. Areobic (Mito.) slow, need carrier to cross in to mito matrix

2. Anaerobic (cytosol) fast convert pyruvate to lactate, causes formation of NAD+

Term
Allosteric Regulation of PFK-1
Definition

1. Inhibitors - ATP  Citrate

2. Activators -ADP, AMP and fructose 2,6-bisphos

(made by PFK-2 from Fru-6P)

Term
PPP
Definition

1. Glc-6P -->Ribose 5P

2. Produce NADPH, for biosynthesis and keeping antioxidants active

3. Ribose 5p precusor for RNA/DNA

 

Term
Coenzyme A components
Definition

1. ADP

2. Pantothenic acid (vitamin B)

3. Reactive thiol group to

form thioester bond

Term

Pyruvate Dehydrogenase RXN

(General)

 

Definition

1. Irreversible

2. Pyruvate, CoA, NAD+ in

3. NADH, Acetyl-CoA, CO2 out

4. Cofactors

TPP, Lipoate, FAD (NAD+ CoA)

Term

Pyruvate Dehydrogenase RXN

Step 1

Definition

1. Pyruvate transfers acetyl group to TPP thiazolium ring and

CO2 is released

2. Irreversible

Term

Pyruvate Dehydrogenase RXN

Step 2

Definition
Oxidized Lipoic acid picks up acetyl group and gets reduced
Term

Pyruvate Dehydrogenase RXN

Step 3

Definition
Acetyl group is transferred to CoA
Term

Pyruvate Dehydrogenase RXN

Step 4

Definition

Reduced Lipoic acid is oxidized by FAD, which becomes FADH2

FADH2 is oxidized by NAD+

Term

Pyruvate Dehydrogenase

 Regulation

(Neg feedback)

Definition
Step 3 & 4 are reversible, so forward activity is decreased with high product concentration
Term

Pyruvate Dehydrogenase

regulation

(Covalent modification)

Definition

1. PDC is activated when dephosphoralated by

PD phosphatase

(activated by Insulin)

2. Deactivated by PD kinase

PD kinase is activated by high Acetyl-CoA, NADH

inactivated by ADP Pyruvate

Term

TCA

General

Definition

1. Acetyl CoA added in, uses 1 H2O

2. Produces

2 CO2

3 NADH

1 FADH2

1 GTP/ATP

Term
Citrate Synthase
Definition

1. Step 1

2. Oxaloacetate + Acetly-CoA -->

Citrate

3. Large -ΔG, drives forward rxn

Term
Aconitase
Definition

1. Step 2

2. Citrate --> Isocitrate

3. Remove then add a H2O

4. Reversible rxn

Term
Isocitrate Dehydrogenase
Definition

1. Step 3

2. Isocitrate --> α-ketogluterate

3. Make NADH CO2

 

Term
α-Ketogluterate Dehydrogenase complex
Definition

1. Step 4

2. α-ketogluterate--> Succinyl-CoA

3. Produce NADH and  CO2, back to 4C structure

4. Same mechanism as pyruvate dehydrogenase complex

5. Large -ΔG

Term
Succinyl-CoA Synthetase
Definition

1. Step 5

2. Succinyl-CoA--> Succinate

3. Make GTP/ATP release CoA

4. Reversible, low ΔG due to fomration of GTP/ATP

Term
Succinate Dehydrogenase
Definition

1. Step 6

2. Succinate--> Fumarate

3. Produce FADH2

4. aka. Complex II in e- trans. chain

5. Reversible ΔG=0

Term

Fumarse

 

Definition

1. Step 7

2. Fumarate--> Malate

3. Add H2O

4. Reversible small ΔG

5. Also done in cytosol

Term
Malate Dehydrogenase
Definition

1. Step 7

2. Malate --> Oxaloacetate

3. Produce NADH

4. Large pos ΔG, rxn is dirven by low product concentration

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