BIOL4: Respiration

Name the order in which aerobic respiration occurs.
1) Glycolysis

2) Link reaction

3) Krebs cycle

4) Oxidative phosphorylation
What does glycolysis produce?
2 pyruvate + 2 ATP
What does the link reaction produce?
Reduced NAD, CO2, acetylcoenzyme A.

What does the Krebs cycle produce?
3 reduced NAD, 1 reduced FAD. 1 ATP per cycle (2 ATP per glucose).
What does oxidative phosphorylation produce?
Oxidises reduced NAD and reduced FAD. Produces water.
32 ATP molecules are produced from 1 glucose molecule. Explain where they come from.
Glycolysis: 2 reduced NAD, 2 ATP
Link reaction: 2 reduced NAD
Krebs cycle: 6 reduced NAD, 2 reduced FAD, 2 ATP.

Each reduced NAD nets 2.5 ATP; each reduced FAD nets 1.5 ATP.
What does anaerobic respiration in plants and animals produce?
In plants: ethanol and CO2.

In animals: lactate.
Describe the process of glycolysis.
1) Using 2x ATP, 1 glucose is converted to 2x triose phosphate.

2) 2x triose phosphate is converted to 2x pyruvate, with 4 ATP being produced. Therefore, there is a net gain of 2 ATP from each molecule of glucose.

3) Converting triose phosphate to pyruvate is an oxidation reaction. 2x NAD, a coenzyme, gets converted to 2x reduced NAD as a result.
Describe the process of the link reaction.
1) Energy is still available in pyruvate. Pyruvate combines with coenzyme A, using NAD, producing acetylcoenzyme A and reduced NAD.

2) Two carbon atoms enter the Krebs cycle. One goes on to form CO2 as waste.
Describe the process of the Krebs cycle.
1) Acetylcoenzyme A (2C), from the link reaction, combines with oxaloacetate (4C) to produce citrate (6C).

2) In a series of oxidation reactions, citrate is converted back to oxaloacetate, giving off 2x CO2, 1x ATP, 3x reduced NAD, and 1x reduced FAD. The reduced NAD and FAD are passed onto the electron transport chain for oxidative phosphorylation.
Describe the process of oxidative phosphorylation.
1) Hydrogen atoms are released as reduced NAD and reduced FAD are oxidised to NAD and FAD. Hydrogen is then split into H+ and e-.

2) The electrons move along the electron transport chain, made up of three electron carriers, losing energy at each carrier.

3) This energy is used to pump protons from the mitochondrial matrix into the intermembrane space. The concentration of protons is now higher in the intermembrane space, so an electrochemical gradient is formed.

4) Protons move down this gradient, back to the matrix, via ATP synthase. This movement drives the synthesis of ATP from ADP and Pi. This movement is called chemiosmosis.

6) In the matrix, at the end of the transport chain, the protons, electrons, and O2 (from the blood) combine to form water. O2 is the final electron acceptor.
Why is anaerobic respiration needed?
If O2 supply is insufficient.
What is the only stage in anaerobic that produces ATP and what does this imply?
Glycolysis; this implies anaerobic respiration is not very efficient.
Describe the process of anaerobic respiration in plants.
1) The pyruvate molecule formed at the end of glycolysis is oxidised by reduced NAD (produced in glycolysis), forming CO2, ethanol, and NAD.

2) This NAD can then be reused in glycolysis.
Describe the process of anaerobic respiration in animals.
1) The pyruvate molecule formed at the end of glycolysis is oxidised by reduced NAD (produced in glycolysis), forming lactate and NAD.

2) This NAD can then be reused in glycolysis.