Lesson 5: The Electron Transport Chain and Chemiosmosis

Question 1

Electron Transport Chain (ETC) 1

Answer 1

Most of the ATP production occurs here

Takes place on the inner mitochondrial membrane of the cristae and in the
intermembrane space

The inner membrane contains proteins called electron carriers, which pick up
electrons and pass them from one to another in a series of redox reactions.

The inner membrane of the mitochondria is folded into cristae to increase the
surface area for the proteins of the electron transport chain.

Question 2

Electron Transport Chain (ETC) 2

Answer 2

Electrons from NADH + H+ and FADH2 are transferred to an electron carrier
protein.

During this process energy is released and used to pump a proton (H+) into
the intermembrane space from the matrix of the mitochondria.

Lowering the pH of the intermembrane space.

The electrons are then transferred to two further protein carriers and the
process is repeated.

As electrons from one NADH + H+ pass along the chain a total of nine protons
are pumped into the intermembrane space. FADH2 misses the first protein in the
chain so only pumps six protons.

Question 3

Oxidative Phosphorylation

Answer 3

At the end of the ETC, the electrons are combined with protons and oxygen to
make water in the oxidative part of oxidative phosphorylation this ensures that
the H+ concentration gradient is maintained.

In the phosphorylation stage, protons move through an integral protein
containing ATP synthase, along their concentration gradient. This completes the
release of energy and a phosphate group is bound to ADP to produce ATP.

Question 4

Chemiosmosis

Answer 4

The intermembrane space of the mitochondria is extremely narrow allowing for
rapid increase in concentration as protons are pumped into it.

This creates the concentration gradient across the membrane between the
intermembrane space and the matrix.

The concentration gradient allows the protons to flow passively through the
integral protein containing ATP synthase back into the matrix.

ATP synthase joins ADP and Pi to form ATP. Three protons passing through the
protein result in one ATP being formed.

Since the electrons from one NADH + H+ pump nine protons into the
intermembrane space, each results in the formation of three ATP. FADH2 only
forms two ATP.

Question 5

Steps of Chemiosmosis

Answer 5

NADH + H+ supplies a pair of hydrogen atoms to the first electron carrier in the
chain. NAD+ returns to the matrix.

Hydrogen atoms are split to release two electrons that will move throughout the
chain. Energy is released as the electrons pass from carrier to carrier. This
energy is used to pump the protons across the membrane into the
intermembrane space.

The electrons are transferred to oxygen at the end of the chain in order to keep
the electrons flowing through the chain.

Protons pass back into the matrix along their concentration gradient.