The Electron Transport Chain (ETC)

Electron Transport Chain

A sequence of electron carrier molecules (membrane proteins) that shuttle electrons during the redox reactions that release energy used to make ATP.

Redox reactions

A chemical reaction involving the transfer of one or more electrons from one reactant to another; also called oxidation-reduction reaction.

Photosynthesis; Redox Reactions

Electron transport chains are the cellular mechanisms used for extracting energy from sunlight in ________ and also from _________, such as the oxidation of sugars (respiration).

Pumping

Passage of electrons between donor and acceptor releases energy, which is used to generate a proton gradient across the mitochondrial membrane by actively _______ protons into the intermembrane space, produces a thermodynamic state that has the potential to do work.

The entire process is called oxidative phosphorylation, since ADP is phosphorylated to ATP using the energy of hydrogen oxidation in many steps.

Why is the entire process called oxidative phosphorylation?

oxidative phosphorylation

What is an enzymatic process in cell metabolism that synthesizes ATP from ADP?

Proton Gradient

What is a gradient formed by the difference in proton concentrations across a membrane?

NADH

In eukaryotes, what is the most important electron donor?

An electron carrier that stores energy used to make ATP

What is NADH?

The most important transport proteins, use energy from ATP to pump protons out of the cell

What are proton pumps?

Oxidative Phosphorylation

In ___________, electrons are transferred from a high-energy electron donor (e.g., NADH) to an electron acceptor (e.g., O2) through an electron transport chain.

Photophosphorylation

In _________________, the energy of sunlight is used to create a high-energy electron donor and an electron acceptor. Electrons are then transferred from the donor to the acceptor through another electron transport chain.

2 hydrogen ions and 2 electrons start the chain. Oxygen and ADP are also reactants.

What are the initial reactants which start the electron transport chain?

3 ATP and a water molecule

What are the final products of the chain?

The first reaction is exothermic while the second reaction is endothermic.

What is a coupled reaction?

Removal of hydrogen is oxidation

When NADH converts back to NAD+, is this oxidation or reduction?

Addition of hydrogen is reduction

When CoQ converts to CoQH2, is this oxidation or reduction?

Change in oxidation state from +3 to +2 is a reduction.

When iron +3 ions add an electron to become +2 ion, is this oxidation or reduction?

Oxidation

What is the process of oxidizing?

Reduction

Definition: Any process in which electrons are added to an atom or ion (as by removing oxygen or adding hydrogen).