Chapter 20 Electron-Transport Chain

Flashcards about the electron-transport chain and oxidative phosphorylation.

What is the primary function of the electron-transport chain?

To transfer the energy of the oxidation of carbon fuels to the energy of a proton gradient.

What is the overall process that includes the citric acid cycle and oxidative phosphorylation called?

Cellular respiration or simply respiration.

What is the role of an inorganic compound in respiration?

Serves as the ultimate electron acceptor.

What two processes are coupled by transmembrane proton fluxes?

Oxidation and ATP synthesis

Where do the electron-transport chain and ATP synthesis occur in eukaryotes?

In the mitochondria.

Where does the citric acid cycle occur within the mitochondria?

The mitochondrial matrix.

What makes the outer mitochondrial membrane permeable to most small ions and molecules?

Mitochondrial porin (channel protein).

What is the name given to the folds of the inner mitochondrial membrane?

Cristae.

Where does electron transport and ATP synthesis take place?

The inner mitochondrial membrane.

Where do the citric acid cycle and fatty acid oxidation occur?

The matrix.

What is the reduction potential (E0′)?

A measure of a molecule’s tendency to donate or accept electrons.

What kind of reducing agent readily donates electrons?

A strong reducing agent.

What kind of oxidizing agent readily accepts electrons?

A strong oxidizing agent.

What happens to energy when high-energy electrons are transferred to oxygen?

Energy is released and used to establish a proton gradient.

Name four types of electron carriers found in the electron-transport chain complexes.

Flavin mononucleotide (FMN), iron–sulfur proteins, cytochromes, and coenzyme Q (Q).

What mobile electron carrier binds protons as well as electrons and can exist in several oxidation states?

Coenzyme Q.

What is the Q pool?

Oxidized and reduced Q present in the inner mitochondrial membrane

What is the function of Frataxin?

A mitochondrial protein required for the synthesis of iron–sulfur clusters.

Name the three large protein complexes through which electrons flow from NADH to O2.

NADH-Q oxidoreductase (Complex I), Q-cytochrome c oxidoreductase (Complex III), and cytochrome c oxidase (Complex IV).

Which complex delivers electrons from FADH2 to Complex III but is not a proton pump?

Succinate-Q reductase (Complex II).

What occurs in Complex I?

Electrons from NADH are passed along to Q to form QH2, and four protons are simultaneously pumped out of the mitochondria.

Where do electrons from FADH2 enter the electron transport chain?

Ubiquinol (Q pool).

What complex does Succinate dehydrogenase belong to?

Succinate-Q reductase (Complex II)

What role does Coenzyme Q play?

Dietary supplement, that boosts energy, enhances the immune system, and acts as an antioxidant.

What reaction is catalyzed by Q-cytochrome c oxidoreductase (Complex III)?

Reduction of two molecules of cytochrome c, using electrons from QH2.

What mechanism couples electron transfer from QH2 to cytochrome c?

The Q cycle.

What is the function of cytochrome c oxidase?

Accepts four electrons from four molecules of cytochrome c in order to catalyze the reduction of O2 to two molecules of H2O.

Why are some protons called 'chemical protons' in the cytochrome c oxidase reaction?

Because they participate in a clearly defined reaction with O2 to form water.

Why are some protons called 'pumped protons' in the cytochrome c oxidase reaction?

Because they are transported out of the matrix, doubling the efficiency of free-energy storage.

Why are the electrons carried by FADH2 not as energy-rich as those carried by NADH?

Because of their different points of entry and roles in the electron transport chain (ETC).

How does Amytal affect the electron transport chain?

Inhibits electron flow through Complex I

What is the respirasome composed of?

Two copies each of Complex I, Complex III, and Complex IV.

What results in the creation of a dead zone?

Agricultural runoff.

What chemicals other than oxygen can be used as the final electron acceptor in anaerobic respiration?

None of these electron acceptors are as electropositive as O2

What are reactive oxygen species (ROS)?

Highly reactive oxygen derivatives generated by partial reduction of O2.

What enzymes help protect against ROS damage?

Superoxide dismutase and catalase.

What is dismutation?

A reaction in which a single reactant is converted into two different products.

Which enzyme complexes catalyzes the reduction of oxygen to water during oxidative phosphorylation?

Cytochrome c oxidase

Which of the following carriers in the electron-transport chain is a protein (as opposed to a small molecule)?

Cytochrome c

What enzyme transforms the energy of protons falling down an energy gradient into ATP?

Mitochondrial enzyme ATP synthase