Electron Transport Chain / Oxidative Phosphorylation

Question 1

Describe the location where the ETC occurs in the mitochondria by referring to one or more of the mitochondrial matrix, inner membrane, intermembrane space and outer membrane.

Answer 1

Complexes I to IV that make up the electron transport chain (enzymes) are
embedded within the inner membrane of the mitochondria.
Hence, the electron
transport chain takes place in the inner membrane of the mitochondria where the
complexes are located.

Question 2

Describe the location where OP occurs in the mitochondria by referring to one or more
of the mitochondrial matrix, inner membrane, intermembrane space and outer membrane.

Answer 2

In some way the matrix, inner membrane and intermembrane space are all involved in OP.
Hydrogen ions are pumped from the matrix into the intermembrane space through
complexes I, II and IV of the ETC (located in the inner membrane).
Once enough of
the H+ have built up in the intermembrane space (between the inner and outer
mitochondrial membrane) the H+ move back into the matrix via ATP synthase (generating ATP), which is located in the inner membrane.

Question 3

What is the starting input (reactant) for ETC and what is the final output (end products)?
Why is the final output important?

Answer 3

The starting input for the ETC are the electron rich coenzymes NADH and FADH2 which off-load their electrons (via a redox reaction) to begin the ETC.
Oxygen is also required as the final electron acceptor, creating H2O.
If oxygen is not available, ETC stops, so does OP and ATP production ceases.

Question 4

Where does the input required for the ETC come from?

Answer 4

The main source of NADH
and FADH2 is the citric acid cycle.
In each CAC, 3 NADH and 1 FADH2 are generated before being taken to the ETC.

Question 5

What makes the ETC coupled to oxidative phosphorylation (OP)?

Answer 5

The ETC is coupled to OP because OP can not occur without the ETC.
As the ETC passes electrons along the chain, the protein complexes of the ETC allow H+ to move from the matrix into the intermembrane space.
OP relies on the H+ in the
intermembrane space to move back into the matrix through the ATP synthase
protein.
As H+ moves through ATP synthase the energy generated is used to attach
a phosphate unit to ADP which regenerates ATP. The majority of the cells ATP is
generated through OP.

Question 6

What is the final output OP?

Why is this output important?

Answer 6

The final output of OP is ATP.
The more H+ that move through ATP synthase during
OP, the more ATP is made.