12.3: Oxidative Phosphorylation

Question 1

Where does oxidative phosphorylation take place

Answer 1

Within the inner folded membrane (cristae)

Enzymes for ATP synthesis (ATP synthase) are stored here.

Question 2

Where would there be more mitochondria/densely packed cristae

Answer 2

Metabolically active cells, such as the liver, muscles and epithelial cells which carry out active transport.

These cells have:

1. Denser cristae to provide a greater surface area of membrane incorporating enzymes involved in oxidative phosphorylation

Question 3

Process of Oxidative Phosphorylation

Answer 3

1. The hydrogen atoms produced during glycolysis and the krebs cycle combine with NAD and FAD to produce reduced NAD/FAD
2. the reduced NAD/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. 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 before they diffuse back into the mitochondrial matrix through ATP synthase channels embedded in the inner mitochondrial membrane.
5. The movement of protons through this channel causes the shape of ATP synthase channels leading to ATP synthesis.
6. At the end of the chain, the electrons combine with these protons and oxygen to form water. Oxygen is the final acceptor

Question 4

Alternate respiratory substances

Answer 4

1. Lipids

2. Proteins

Question 5

Respiration of lipids

Answer 5

1. Lipids are hydrolysed to glycerol and fatty acids
2. The glycerol is phosphorylated and converted to triose phosphate which enters the glycolysis pathway and the krebs cycle.
3. The fatty acids are broken down into 2-carbon fragments which are converted into acetylcoenzyme-A. This enter the krebs cycle

Question 6

Products of the respiration of lipds

Answer 6

1. 2-Carbon fragments of carbohydrate
2. Many hydrogen atoms

Lipids release twice the energy of the same mass of carbohydrate

Question 7

Respiration of proteins

Answer 7

1. Proteins are first hydrolysed into their constituent amino acids
2. These amino acids have their amino group removed before entering the respiratory pathway at different stages

3:
3-carbon compounds are converted into pyruvate
4 & 5 carbon compounds are converted into intermediates for the krebs cycle.