Energy Transfer In And Between Organisms: - Link Reaction And Krebs Cycle.

- Link reaction and Kreb cycle - 

Link reaction: 

Pyruvate is oxidised to acetate // pyruvate loses a CO₂ and (X2) H // H is accepted by NAD to reduced NAD later used to produce ATP. 

2-Carbon acetate combines coenzyme A (CoA) = acetylcoenzyme A 

Krebs cycle

2-Carbon acetylcoenzyme A from link reaction combined with the 4-carbon molecule to produce a 6-carbon molecule. 

6-Carbon molecule loses carbon dioxide and hydrogen to give 4-Carbon molecules and single molecule of ATP produced as result of substrate-level phosphorylation 

4-Carbon molecule combines with new molecule of acetylcoenzyme A // cycle starts again. 

Pyruvate, link reaction and krebs cycle produces 

- Reduced coenzymes NAD and FAD // by oxidative phosphorylation potential to provide energy to produce ATP 

- 1 ATP molecule 

- 3 CO₂ molecules

2 Pyruvate molecules produced for each original glucose molecule. 

Coenzymes = molecules that enzymes require to function, includes:

NAD - important throughout repsiration 

FAD - important in the Kreb cycle 

NADP - important in photosynthesis

Respiration NAD important carrier // works with dehydrogenase enzymes catalyse removal hydrogen atoms from substrates transfer them to the other molecules involved in oxidative phosphorylation. 

Kreb cycle is important for: 

Breaking down pyruvate into CO₂ 

Producing hydrogen atoms carried by NAD to electron transfer chain prodivde energy for oxidative phosphorylation = ATP produced 

Regenerates 4 carbon molecule combines with acetylcoenzyme A 

Source of intermediate compounds used by cells - fatty acids, amino acids and chlorophyll.