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Link Reaction(In mitochondria Matrix)

Pyruvate will entermitochondria to be

converted to Acetyl-CoAin a reaction known as :

(Inside Mitochondria)

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Link reaction

Pyruvateenters thematrix ofmitochondrionvia activetransport.

2

Pyruvate is decarboxylated to form 2-carbon acetyl group the removed carbon is released as CO2.Acetyl group is oxidised with the formation of NADH and itcombines with Coenzyme A (CoA) to form acetyl CoA.

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The acetyl group passes into acyclic reaction and combines witha 4C molecule (oxaloacetate) tofrom a 6C molecule (citrate).

The CoA is released for reuse.

6C molecule (citrate) is oxidisedto form a 5C molecule, NAD+ is

Krebs cycle (In mitochondria Matrix)

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.

5C molecule is oxidised anddecarboxylated to form 4Cmolecule.

CO2 is released.

Another NAD+ is reduced to formNADH.

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The 4C molecules undgoesseveral changes resulting inthe following products:

- another NADH formed- FAD is reduced to FADH2- reduction of ADP to ATP

The 4C molecules is

Krebs cycle (In mitochondria Matrix)

4

to reform the startingmolecule of the cycle,oxaloacetate.

Oxaloacetate may begin the

cycle again

NAD= nicotinamide adenine dinucleotidFAD= flavin adenine dinucleotide

http://www.mcgrawhill.ca/school/applets/abbio/quiz/ch05/how_the_krebs_cycle_wor.swf

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Summary of Krebs cycle

INPUT per turn OUTPUT per turn

1 Acetyl CoA 2 Carbon Dioxide

1 ADP + 1Pi 1 ATP

3 NAD+ 3 NADH

5

2

Note that 2 molecules of pyruvate (& thus 2molecules of acetyl CoA) are produced from each

glucose molecule.

Hence, the Krebs cycle has to turn twice for eachglucose oxidised.

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Glycolysis, Link Reaction, Kreb Cyclegenerates large amounts of reducedelectron Carriers. i.e NADH, FADH2

A lot of energy is still trapped within thesemolecules

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But How do we get Energy (ATP) fromReduced Electron Carriers (NADH, FADH2)?

Via Oxidative Phosphorylation!

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Process by which ATP is formed as

e- are transferred from NADH or FADH2to O2

via a series of electron carriers

Oxidative Phosphorylation(Occur on the inner mitochondrial membrane and on the membrane of cristae)

Oxidative because it involvesoxidation (loss of e-) of NADH or FADH2.

phosphorylation because it involvesaddition of Pi to ADP to form ATP.

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Electron Transport For reduced NADHydrogen atomscarried by by NADHare released at thecristae and split intohydrogen ions (or

protons or H+) andelectrons.

The electrons pass

Enrichment

8Electrons from NADH pass through all the carriers in theelectron transport chain and drive all three proton pumps

chain, losing energyas they pass fromone carrier to thenext.

Oxygen is the finalelectron acceptorand combine withhydrogen atoms toform water.

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Electron Transport For reduced FADHydrogen atomscarried by byFADH2 are releasedat the cristae andsplit into split into

hydrogen ions (orprotons or H+) andelectrons.

The electrons ass

Enrichment

9Electrons from FADH2 do not pass through all the carriers inthe electron transport chain; they drive two of the three protonum s.

along the transportchain, losing energyas they pass fromone carrier to thenext.

Oxygen is the finalelectron acceptorand combine withhydrogen atoms to

form water.

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Oxidative Phosphorylation= Electron Transport chain + Chemiosmosis

Enrichment

10

Accumulation of protons (hydrogen ions) in in the intermembrane space creates aproton gradient. Protons pass down the gradient through ATP synthase moleculesand produce ATP from ADP and Pi.

1 NADH yields 3 ATP1 FADH2 yields 2 ATP

Oxygen is the final electron acceptor andcombine with hydrogen atoms to form water.

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Stages ATPproduced

Glycolysis- used 2ATP- made 4ATP(substrate phosphorylation)- yield 2 NADH

2

Link reaction- yield 2 NADH

Krebs cycle

Summary of ATP production

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- made 2ATP(substrate phosphorylation)- yield 2 FADH2- yield 6 NADH

2

Oxidative Phosphorylation- 10 NADH yield 30 ATP- 2 FADH2 yield 4 ATP

304

Maximum Total Yield fromone molecule of glucose 38

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Summary of ATP production

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Diagram from Biological Science 1 by N.P.O. Green, G.W. Stout, D. J. Taylor, Cambridge University Press