1.7 - Cellular Respiration

Stage 1 - Glycolysis
1. Occurs in the cytoplasm
2. Occurs in the presence or absence of oxygen
3. Phase 1 - Energy Investment
  1. ATP broken down
    1. This provides energy
  2. First phosphorylation occurs
    1. Addition of phosphate to a molecule
    2. Phosphate from breakdown of ATP is added onto glucose
      1. Forms intermediate compounds
        Intermediates can continue onto a number of pathways
4. Phase 2 - Energy Pay Off
  1. ATP generated
    1. Net gain of 2 ATP
  2. Second phosphorylation occurs
    1. Phosphate added to intermediates to form pyruvate
  3. Catalysed by phosphofructokinase
  4. Irreversible reaction leading to glycolytic pathway
5. Dehydrogenase enzymes remove hydrogen ions and electrons which are passed onto coenzyme NAD
  1. Forms NADH
Stage 2 - Citric Acid Cycle
1. Occurs in the matrix of the mitochondria
2. Requires the presence of oxygen
3. Pyruvate is broken down into an acetyl group
4. Acetyl group combines with coenzyme A
  1. Forms acetyl coenzyme-A
5. Acetyl Co-A is transferred to the citric acid cycle
6. Acetyl Co-A combines with oxaloacetate
  1. Forms citrate
7. A series of enzyme mediated steps converts citrate back to oxaloacetate
8. Cycle produces CO2 and generates ATP
9. Dehydrogenase enzymes remove hydrogen ions and electrons which are passed onto conezymes NAD and FAD
  1. Forms NADH and FADH2
Stage 3 - Electron Transport Chain
1. Occurs on a collection of proteins (cristae) attached to the inner mitochondrial membrane
2. Coenzymes NADH and FADH2 release high energy electrons to the electron transport chain
3. High energy electrons pass along the chain and release energy
  1. Energy is used to pump hydrogen ions across the inner mitochondrial membrane
4. Hydrogen ions flow black through the membrane
  1. ATP is synthesised using the membrane protein ATP synthase
    1. Provides the bulk of ATP generated by cellular respiration
5. The final electron acceptor is oxygen
6. Oxygen combines with hydrogen ions and electrons
  1. Forms water
Respiratory Substrates
1. Starch and glycogen are broken down to glucose
2. Other sugar molecules are converted to glucose or a glycoloysis intermediate
3. Proteins can be broken down to amino acids
  1. Converted to intermediates of glycolysis and citric acid cycle
4. Fats can be broken down to intermediates of glycoloysis and citric acid cycle

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1.7 - Cellular Respiration

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	Created by Calum Mooney over 8 years ago