ATP and Respiration Notes - Detailed

Detailed notes on ATP structure and suitability to role and all the stages involved in aerobic and anaerobic respiration.



Anaerobic Respiration in Plants and Animals

The Link Reaction

The Krebs Cycle

Oxidative Phosphorylation

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AQA Biology Unit 4: Section 2 ­ Energy Supply
ATP & Cellular Respiration
Cellular Respiration ­ the process of deriving energy from glucose (in the form of ATP).
Before energy can be utilised by our cells it must be turned into ATP (Adenosine Triphosphate) ­ a
specific shortterm energy storage unit. It is the `currency' of energy exchange in cells.
Adenosine Triphosphate is made of the nucleotide base adenine , combined with a ribose sugar
and three phosphate groups . Diffusing easily through membranes it carries energy to areas of the
cell its needed. It is synthesised from ADP and an inorganic phosphate molecule (iP) in a process
called phosphorylation that is catalysed by the enzyme ATP synthase .
ATP can be converted back into ADP + iP through the
addition of water (hydrolysis ). ATP is relatively unstable ­ one of the three phosphate groups can
easily be discarded, releasing energy. ATP can therefore easily donate inorganic phosphates to
different molecules ­ substratelevel phosphorylation.
A large store of ATP is kept in cells for a short amount of time, as ATP is the cell's immediate
source of energy.
Properties making it suitable as an immediate energy source/ shortterm store:
energy released in small, manageable quantities ­ no energy wasted
easily broken down / hydrolysed into ADP and iP ( in one stage, not many as with glucose)
­ energy released quickly
small and soluble molecule ­ easily transported around cell
can transfer energy between molecules easily by transferring a phosphate group
ATP cannot pass out of the cell ­ always an immediate source of energy
Cellular Respiration occurs in 4 steps:
1) Glycolysis ­ in the cytoplasm
2) The Link Reaction ­ across the innermitochondrial membrane
3) The Krebs Cycle ­ across the innermitochondrial membrane
4) The Electron Transport Chain/ Oxidative Phosphorylation ­ across the innermitochondrial
Role of CoEnzymes & Enzymes:

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AQA Biology Unit 4: Section 2 ­ Energy Supply
Bring together iP + ADP to form ATP ( ATP synthase ­ an enzyme)
Transport electrons and protons in the form of Hydrogen ( NAD & NADH , and FAD & FADH2 ­
coenzymes and reduced coenzymes )
Coenzymes are molecules that aid the function of an enzyme. They work by transferring a
chemical group from one molecule to another.…read more

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AQA Biology Unit 4: Section 2 ­ Energy Supply
Krebs Cycle
This is an AEROBIC REACTION: can only occur when oxygen is present.
Occurs across the innermembrane of the mitochondria.
Acetyl CoA (2C ) combines with Oxaloacetate (4C Compound). Citric Acid (or Citrate ) is formed (a
6C Compound ). Co Enzyme A rejoins the Link Reaction.…read more

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AQA Biology Unit 4: Section 2 ­ Energy Supply
pumped. Therefore, less protons are pumped across the membrane per FADH2 , meaning less
ATP is formed as a result.
During Oxidative Phosphorylation therefore, 34 ATP molecules are produced. Therefore, from one
glucose molecule, 38 ATP are produced altogether (4 ATP having been produced in earlier stages).…read more


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