The Krebs Cycle

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  • Created by: J.E.C.
  • Created on: 14-10-13 20:01

Overview

> Involves a series of oxidation-reduction reactions that take place in the matrix of the mitochondria

> The 2-carbon Acetyl CoA combines with a 4-carbon molecule to produce a 6-carbon molecule

> The 6-carbon molecule loses CO2 and hydrogens to give a 4-carbon molecule & a single molecule of ATP > produced as a result of substrate-level phosphorylation

> The 4-carbon molecule can now combine with a new molecule of acetyl CoA to begin the cycle again

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For each molecule of pyruvate...

The link reaction & Krebs cycle therefore produce:

> Reduced coenzymes such as NAD & FAD, which have the potential to produce ATP molecules

> One molecule of ATP

> Three molecules of CO2

> However, two molecules of pyruvate are produced for every glucose, so the quantities above are doubled

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Coenzymes

> Molecules that some enzymes require in order to function

> Carry hydrogen atoms from one molecule to another in photosynthesis & respiration

> NAD - important throughout respiration

> FAD - important in the Krebs cycle

> NADP - important in photosynthesis

> NAD is the most important carrier when it comes to repiration, working with enzymes that catalase the removal of hydrogen ions from substrates and then transfers them to other molecules, such as hydrogen carriers involved in oxidative phosphorylation

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The significance of the Krebs Cycle

> Breaks down macromolecules into smaller ones, pyruvate into CO2

> Produces H atoms that are carried by NAD to the electron transport chain for oxidative phosphorylation. Leads to the production of ATP, whcih provides metabolic energy for the cell

> Regenerates the 4-carbon molecule that combines with Acetyl CoA, whcih would otherwise accumulate

> Source of intermediate compounds used by cells in the manufacture of other important substances such as fatty acids, amino acids & chlorophyll

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