Oxidative Phosphorylation 18.4

Question 1

Explain what happens during oxidative phosphorylation

Answer 1

• The NADHs and FADH2s are delivered to the electron transport chain which are carrier proteins embedded in the inner mitochondrial membrane.
• The hydrogen atoms from the reduced coenzymes dissociate into H+ ions and electrons. This is oxidation
• The electrons are excited so are used in the etc for chemiosmosis to occur. The electrons oxidise electron carriers as they flow through the etc.
• This energy causes protons to be pumped from the mitochondrial matrix to the intermembrane space
• This creates a proton gradients which leads to the diffusion of protons through a hydrophilic membrane channel that is attached to ATP synthase
• ATP is then synthesised because the protons release energy as they travel through.
• The protons end up back at the matrix and the electrons at the end of the etc will combine with protons and oxygen to form water.

Question 2

Why does the electron transport chain not function without oxygen?

Answer 2

Oxygen is the final electron acceptor so the etc cannot operate without it as the electrons in the etc wouldn’t be accepted

Question 3

Why can’t the hydrogens released from the NADH and FADH2 just combine with the oxygen?

Answer 3

This wouldn’t provide the energy needed for ATP to be synthesised, it would just raise the temperature of the cell

Question 4

How many ATPs are made from oxidative phosphorylation?

Answer 4

30 because NAD results in 3 ATPS being made and FAD is 2.

Question 5

How many ATPs are made in total in aerobic respiration for each step?

Answer 5

38 in total

• 2 from glycolysis
• 0 in the Link reaction
• 2 made in Krebs
• 30 made from oxidative phosphorylation
• 4 made from substrate-level phosphorylation

Question 6

Why is it unlikely you will use 38 ATP molecules?

Answer 6

You will never use all of them as they will be used up for other things. Some are used for reductions, some are used to make pyruvate in the matrix…