Breaks down macromolecules into smaller one;
pyruvate is broken down into carbon dioxide
Produces hydrogen atoms that are carried by NAD to the
electron transport chain for oxidative phosphorylation
Produces ATP that provides metabolic energy for the cell
Regenerates the 4-carbon molecule that combines with
acetylcoenzyme A, which would otherwise accumulate
It is a source of intermediate compounds used by cells in the manufacture of
other important substances such as fatty acids, amino acids and chlorophyll
Coenzymes
NAD
Hydrogen carrier - important for respiration
FAD
Important in Krebs cycle
NADP
Important in photosynthesis
Link Reaction
Pyruvate is oxidised by removing hydrogen
The hydrogen is accepted by NAD to form reduced NAD which is later used to produce ATP
The 2-carbon molecule (acetyl group) that is formed combines
with coenzyme A (CoA) to produce acetylcoenzyme A
A carbon molecule is formed from each pyruvate
Pyruvate + NAD + CoA --> acetyl CoA + reduced NAD + CO2
Krebs Cycle
Occurs in the matrix of the
mitochondria
2-carbon acetylcoenzyme A from the link
reaction combines with a 4-carbon molecule
Produces a 6-carbon molecule
The 6-carbon molecule loses carbon dioxide and hydrogens
Gives a 4-carbon molecule and a single molecule of ATP
as a result of substrate-level phosphorylation
The 4-carbon molecule can now combine
with a new molecule of coenzyme A
Begins the cycle again
For each molecule of pyruvate, the link reaction
and Krebs cycle therefore produce:
1 molecule of ATP
3 molecules of carbon dioxide
reduced coenzymes such as NAD and FAD
These have the potential to produce
ATP molecules and therefore the
important products of Krebs cycle