5.2.2 - Respiration Flashcards
Why is cellular respiration needed?
Respiration transfers energy stored in complex organic molecules to ATP which is required for:
- Active transport for the conduction of nerve impulses and uptake of nitrates by root hair cells
- Muscle contraction
- Anabolic processes such as the synthesis of proteins and amino acids for growth and repair of tissues
What is the structure of mitochondria?
- Smooth outer mitochondrial membrane
- Inner mitochondrial membrane which is folded into many cristae
- Matrix
- Mitochondrial DNA
What is the first stage of aerobic and anaerobic respiration?
Glycolysis
Where does glycolysis take place?
In the cytoplasm
What happens during glycolysis?
- 2 ATP molecules break down into 2 ADP molecules
- An enzyme adds the 2 phosphate groups to glucose in a process called phosphorylation
- This produces a molecule of hexose bisphosphate
- Hexose bisphosphate breaks down into 2 molecules of triose phosphate
- Triose phosphate is oxidised and the hydrogen lost is transferred to NAD forming NADH (oxidation-reduction reaction and dehydrogenation)
- Another phosphate group is added resulting in 2 ATP molecules per triose phosphate molecule
- This converts triose phosphate to pyruvate
What is the overall yield of glycolysis?
2 ATP molecules
What happens after glycolysis?
Link reaction
Where does the link reaction take place?
Mitochondrial matrix
What happens in the link reaction?
- Pyruvate is actively transported into the mitochondrial matrix
- A molecule of carbon dioxide is removed (decarboxylation)
- Pyruvate is oxidised and the hydrogen lost is transferred to NAD forming NADH (oxidation-reduction reaction)
- Pyruvate is converted to a molecule of acetate
- A molecule of CoA is added to acetate producing Acetyl-CoA
What happens after the link reaction?
Krebs cycle
Where does the Krebs cycle take place?
Mitochondrial matrix
What happens in the Krebs cycle?
- Acetyl-CoA reacts with a 4 carbon molecule called oxaloacetate
- This forms a new 6 carbon molecule called citrate and loses CoA
- Citrate then undergoes a series of oxidation-reduction reactions to reform oxaloacetate
- During these reactions citrate loses 2 carbon atoms in the form of carbon dioxide
- These reactions produce 3NADH, FADH2 and ATP which is produced in a reaction called substrate-level phosphorylation
What happens after the Krebs cycle?
Oxidative phosphorylation
Where does oxidative phosphorylation take place?
Inner mitochondrial membrane
What happens during oxidative phosphorylation?
- NADH and FADH2 travel to the inner mitochondrial membrane
- They donate electrons to proteins in the membrane producing NAD, FAD and protons
- These electrons move along the proteins known as the electron transfer chain through a series of oxidation-reduction reactions
- As the electrons travel they transfer energy to the proteins which is used to actively transport protons from the matrix into the intermembrane space
- This maintains a proton gradient between the 2 areas
- The electrons at the end of the chain react with oxygen (final electron acceptor) and protons forming water
- As a result of the proton gradient protons in the intermembrane space diffuse by chemiosmosis back into the matrix via ATP synthase
- Chemiosmosis supplies ATP synthase with energy which it uses to catalyse the production of ATP
