Why is respiration important?
● Respiration produces ATP (to release energy)
● For active transport, protein synthesis
Summarise the stages of aerobic respiration
Aerobic respiration
1. Glycolysis - cytoplasm (anaerobic)
2. Link reaction - mitochondrial matrix
3. Krebs cycle - mitochondrial matrix
4. Oxidative phosphorylation - inner
mitochondrial membrane
Summarise stages of anerobic respiration
- Glycolysis - cytoplasm
- NAD regeneration - cytoplasm
Describe the process of glycolysis
- Glucose phosphorylated to glucose phosphate
○ Using inorganic phosphates from 2 ATP - Hydrolysed to 2 x triose phosphate
- Oxidised to 2 pyruvate
○ 2 NAD reduced
○ 4 ATP regenerated- net gain of 2 ATP
Explain what happens after glycolysis if respiration is anaerobic
- Pyruvate converted to lactate (animals & some bacteria) or ethanol (plants & yeast)
- Oxidising reduced NAD → NAD regenerated
- So glycolysis can continue (which needs NAD) allowing continued production of ATP
Suggest why anaerobic respiration produces less ATP per molecule of glucose than aerobic respiration
● Only glycolysis involved which produces little ATP (2 molecules)
● No oxidative phosphorylation which forms majority of ATP
What happens after glycolysis if respiration is aerobic?
Pyruvate is actively transported into the mitochondrial matrix
Describe the link reaction
- Pyruvate oxidised and decarboxylated to acetate
○ CO2 produced
○ Reduced NAD produced (picks up H) - Acetate combines with coenzyme A, forming Acetyl Coenzyme A
Describe the Krebs cycle
- Acetyl coenzyme A (2C) reacts with a 4C molecule
○ Releasing coenzyme A
○ Producing a 6C molecule that enters the Krebs cycle - In a series of oxidation-reduction reactions, the 4C molecule is regenerated and:
○ 2xCO2lost
○ Coenzymes NAD & FAD reduced
○ Substrate level phosphorylation
(direct transfer of Pi from intermediate compound to ADP) → ATP produced
Describe the process of oxidative phosphorylation
- Reduced NAD/FAD oxidised to release H atoms → split into protons (H+) and electrons (e-)
- Electrons transferred down electron transfer chain
○ By redox reactions - Energy released by electrons used in the production of ATP from ADP + Pi (chemiosmotic theory):
○ Energy used by electron carriers to actively pump protons from matrix into intermembrane space
○ Protons diffuse into matrix down an electrochemical gradient, via ATP synthase (embedded)
○ Releasing energy to synthesise ATP from ADP + Pi - In matrix at end of ETC, oxygen is final electron acceptor (electrons can’t pass along otherwise)
○ So protons, electrons and oxygen combine to form water
Give examples of other respiratory substrates
● Fatty acids from hydrolysis of lipids → converted to Acetyl Coenzyme A
● Amino acids from hydrolysis of proteins → converted to intermediates in Krebs cycle
Products of glucose in kreb cycle
6 x reduced NAD, 2 x reduced FAD, 2 x ATP and 4 x CO2
