Recap: structure of ATP

P P P

ribose guanine inorganic phosphate

deoxyribose thymine

organic phosphate

nicotinamide cytosine adenine flavine

Recap: where in the cell?

1. Glycolysis1. Phosphorylation

2. Oxidation

2. Link reaction

3. Krebs cycle

4. Oxidative phosphorylation

Recap: glycolysis

Recap: link reaction

Recap: Krebs cycle

Enzymes

• Glycolysis:– Phosphofructokinase

• Krebs cycle:– Decarboxylases

– Dehydrogenases

Regulatory enzymes

glucose

phosphofructokinase enzyme

pyruvate

Krebscycle

↑ ATP↑ citrate

↑ ADP↓ ATP

↓ citrate

How much ATP has been produced?

• Glycolysis:

• Link reaction:

• Krebs cycle:

Is this enough???

The electron transport chain

The electron transport chain1. Hydrogen atoms released from NADH and FADH as

they are oxidised

2. Hydrogen atoms split into protons and electrons

3. Electrons move along the electron transport chain, losing energy at each carrier

4. Energy is used to pump protons into intermembrane space forming an electrochemical gradient

5. Protons move down electrochemical gradient back to matrix via ATP synthase

6. Movement of protons drives synthesis of ATP from ADP and inorganic phosphate

7. Protons, electrons and oxygen combine to form water, the final electron acceptor

Evidence for chemiosmosis1. pH of intermembrane space is lower than pH of

matrix– Proton gradient exists between intermembrane space and

matrix

2. Artificial vesicles created with proton pump proteins resulted in ↓ pH in vesicle– Proton gradient can be used to synthesise ATP

3. Mitochondria in pH8 solution produced no ATP– Proton gradient can be used by mitochondria to make ATP

4. Uncouplers destroyed proton gradient in mitochondria– Proton gradient is required by mitochondria to make ATP

How much ATP?

• Oxidative phosphorylation makes ATP using energy from NADH and FADH

• 1 NADH → 2.5 ATP

• 1 FADH → 1.5 ATP

More cutbacks:In 1997 1 NADH → 3 ATP and 1 FADH → 2 ATP!

How much ATP?

Stage of respiration Molecules produced Number of ATP molecules

Glycolysis

Link reaction (x2)

Krebs cycle (x2)

Total ATP =

Anaerobic respiration

glucose

pyruvate

carbon dioxide + ethanal

ethanol

lactic acid

Aerobic and anaerobic respiration

Aerobic• Where?

• Is oxidation complete?

• What are the waste products?

• How much energy?

Anaerobic• Where?

• Is oxidation complete?

• What are the waste products?

• How much energy?