Ana/Cataplerotic reactions (12)

Define amphibolic

Anabolism + Catabolism

Define catapleurotic reaction

CAC intermediates are depleted

Define anapleurotic pathways

CAC intermediates are replenished

Then, how can the CAC be described?

As an amphibolic process

1st cataplerotic reaction of the CAC

PEP formation from oxaloacetate using PEPCK

2nd cataplerotic reaction of the CAC

Oxalo. + A-CoA from citrate using ATP-citrate lyase

3rd catapleurotic of the CAC

AAs from ketoglutarate using glutamate dehydrogenase

Sole anaplerotic reaction of the CAC

Oxaloacetate from pyruvat using pyruvate carboxylase

1st amphiplerotic reaction of CAC

Malic enzyme: pyruvate → malate → pyruvate

2nd amphiplerotic reaction of CAC

Transamination between glutamate and ketoglutarate

3rd amphiplerotic reaction of CAC

Transamination between alanine and aspartate

What dictates which molecule will be transaminated?

The cell’s needs in AAs

What is a transamination pair?

Keto acid and amino acid formed once the amino group is moved

What are the 3 sections of the mitochondrion?

1. Inner membrane (proton gradient)

2. Matrix

3. Outer membrane (porous)

How does pyruvate get inside the matrix?

With MPCs and VDAC or mitochondrial pyruvate channels and a voltage-dependent anion channel

How’s the structure of MPCs?

MPC1 and MPC2 homodimer

How does cytosolic NADH get inside the mitochondrion?

With 2 types of shuttles

1st type of shuttle

DHAP/G3P shuttle

Steps of the DHAP/3GP shuttle

1. DHAP reduction into G3P

2. G3P goes through the outer membrane

3. Reoxidation of G3P + Reduction of FAD

4. Transfer of FADH₂ electrons to coQ

2nd type of shuttle

Malate/aspartate shuttle

Steps of the malate/aspartate shuttle

1. Reduction of oxaloacetate to malate

2. Malate transport into matrix

3. Reoxidation of malate

4. Oxidation of NADH → NAD+ by complex I

5. Transamination of oxaloacetate into Asp

6. Reconversion of Asp into oxaloacetate

How is ADP+Pi brought into the mitochondrion?

1. ATP-ADP translocator (antiport)

2. Phosphate carrier (symport)

Where does ox. phos. take place?

Outer membrane

Principle of ox. phos.

Deliver electrons from NADH and FADH₂

Order of electron transfer

C1 → CoQ → C3 → Cyt c →C4 → C5

What else do the complexes 1,3 and 4 do other than é transport?

Generating an electrochemical gradient from pump protons

How many H+ come from NADH?

10

How many H+ come from FADH₂?

6

What is the proton gradient used by?

Complex 5 or ATP synthase (ADP+P_i → ATP)

In what order are the electrons transported?

From low to high potential molecules (weak to strong hold on electron)

What happens to complexes 1, 3 and 4 when they pump protons?

Conformational changes

Why are all the ox. phos. reactions favourable?

Really negative delta G (exergonic)

In what other way can CoQ be reduced?

1. Beta-oxidation of fatty acids

2. G3P dehydrogenase

If all the steps are extremely favourable, why are there so many redox reactions? (why not one big reaction??)

Not to waste energy along the way