Zusammenfassung der Ressource
Link Reaction and Kreb's Cycle
- Significance of Krebs cycle
- 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