12.3 Oxidative phosphorylation

Question 1

Where does oxidative phosphorylation takr place

Answer 1

In the inner mitrochondrial membrane, inside the cristae are the enzyme and other proteins required

Question 2

What does the synthesis of ATP by oxidative phosphorylation involve

Answer 2

The transfer of electrons down a series of electron carrier molecules which forms an electron transfer chain

Question 3

What is the process of oxidative phosphorylation

Answer 3

1. The hydrogen atoms produced during glycolysis an the krebs cycle combine with NAD and FAD
2. The reduced NAD and FAD donate the electrons of the hydrogen atoms they are carrying to the first molecule in the electron transfer chain
3. The electrons pass along a chain of electron transfer carrier molecules in a series of oxidation-reduction reactions. As the electrons flow along the chain, the energy they release causes the active transport of protons across the inner mitochondrial membrane and into inter-membranal space
4. The protons accumulate in the inter-membranal space before they diffuse back into the mitochondrial matrix through ATP synthase channels embedded in the inner mitochondrial membrane
5. At the end of the chain the electrons combine with these protons and oxygen to form water. Oxygen is therefore the final acceptor of electrons in the electron transfer chain.

Question 4

Why is oxygen important in respiration

Answer 4

To act as the final acceptor of the hydrogen atoms produced in glycolysis and the Krebs cycle.

Without its role in removing hydrogen atoms, the hydrogen ions and electrons would back up along the chain and the process of respiration would come to a halt

Question 5

What are the alternative respiratory substrates

Answer 5

1. Proteins

2. Lipids

Question 6

What happens to lipids when they are respired

Answer 6

First they are hydrolysed to glyerol and fatty acids

The glycerol is phosphorylated and is converted to triose phosphate and subsequently the krebs cycle. (acts as glucose)

The fatty acids are broken into 2-carbon fragments which are converted to acetyl coenzyme A

Question 7

What does the oxidation of lipids produce

Answer 7

2 carbon fragments of carbohydrate and many hydrogen atoms. These hydrogen atoms are used in the ETC

Question 8

What happens to proteins when they are respired

Answer 8

It is hydrolysed firstly to its constituent amino acids.

They have their amino group removed before entering the respiratory pathway at different points depending on their number of carbon atoms

3-carbon compounds are converted to pyruvate, 4-carbon compounds and 5-carbon compounds to intermediates in the krebs cycle