5.4 Electron Transport Chain Cell Respiration

Electron Transport Chain (ETC)

a series of proteins which pass high energy electrons to each other; embedded in the inner membrane of the mitochondria.

Where does ETC take place?

• Inner membrane of mitochondria

What happens to NADH and FADH2 as they pass through the ETC

They are oxidized:

• NADH ➞ NAD+

• FADH2 ➞ FAD

NAD+ and FAD will…

re-enter glycolysis and the CAC to pick up more electrons.

As high energy electrons pass through the ETC , the energy from their redox reactions is used to…

pump protons (H+) from the mitochondrial matrix into the intermembrane space, across the inner mitochondrial membrane.

H+ accumulates in…

intermembrane space, establishing an electrochemical gradient (a difference in concentration and charge) across the membrane.

- Intermembrane space increases in H+ concentration.

Exergonic transfer of electrons through the ETC is…

coupled to endergonic pumping of protons against their concentration gradient.

Final step of ETC

electrons are transferred to O2. The O2, protons, and electrons combine to form water (H2O).

• Note: oxygen is the final electron acceptor, forming water in the process.

ATP Synthase

makes ATP from ADP via oxidative phosphorylation, powered by the proton-motive force. Embedded in inner mitochondrial membrane.

Proton-Motive force

energy produced by the movement of protons down an electrochemical gradient (high [H+] in intermembrane space, low [H+] in mitochondrial matrix).

Chemiosmosis

movement of ions down a concentration gradient across a semipermeable membrane.

Protons flow…

down their gradient (from the intermembrane space into the mitochondrial matrix)

through ATP synthase. ATP synthase uses the flow of H+ to make ATP from ADP.

The highly folded mitochondrial inner membrane…

increases surface area for more electron transport

chains, allowing more ATP production.

In prokaryotes, the ETC is embedded in…

the cellular membrane instead of the inner mitochondrial membrane.

The ETC yields a total of

approximately 34 ATP.

ETC produces

by far the most ATP in cellular

respiration.