Cytochromes and Iron-Sulfur Proteins in Respiration

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What is the role of heme c in cytochromes?

It is involved in trans-membrane H+ transport coupled to e- transfer. (correct)

It is bound to 6 sites of Fe, preventing any molecule from approaching.

It absorbs light at characteristic wavelengths.

It carries oxygen only.

How do hemes in the 3 classes of cytochrome (a, b, c) differ?

By the number of propionate side-chains.

By the substituents on the porphyrin ring system. (correct)

By the presence of a covalent link to the protein via thioether bonds.

By the ability to undergo 1 e- transition between ferric and ferrous states.

Which type of transition can the heme iron undergo?

Transition between Fe(III) and Fe(II). (correct)

Transition between Fe(III) and Fe(0).

Transition between Fe(II) and Fe(I).

Transition between Fe(II) and Fe(0).

What is a common feature among the classes of cytochrome hemes?

Presence of thioether bonds to cysteine residues. Signup and view all the answers

What is the function of coenzyme Q (CoQ) based on the text?

Involved in trans-membrane H+ transport coupled to e- transfer. Signup and view all the answers

What is a distinguishing factor of heme c compared to other cytochrome hemes?

Is covalently linked to the protein via thioether bonds. Signup and view all the answers

Which component of the electron transport chain is responsible for transferring electrons from Complex III to Complex IV?

Ubiquinone (CoQ) Signup and view all the answers

What is the prosthetic group present in cytochromes that facilitates electron transfer?

Heme Signup and view all the answers

What is the role of the isoprenoid tail in ubiquinone (CoQ)?

It anchors the molecule to the inner mitochondrial membrane Signup and view all the answers

Which complex of the electron transport chain is responsible for reducing oxygen to water?

Complex IV (Cytochrome c oxidase) Signup and view all the answers

What is the role of the heme prosthetic group in cytochrome c?

It facilitates the transfer of electrons between complexes Signup and view all the answers

Which component of the electron transport chain is responsible for transferring electrons from Complex I to Complex III?

Ubiquinone (CoQ) Signup and view all the answers

Which of the following is the correct order of electron transfer through the cytochromes in the mitochondrial electron transport chain?

Cytochrome b, c1, c, a, a3 Signup and view all the answers

What is the primary function of Coenzyme Q (CoQ) in the electron transport chain?

To act as a mobile carrier, shuttling electrons between Complexes I/II and Complex III Signup and view all the answers

What is the primary structural feature that allows Coenzyme Q (CoQ) to act as a mobile electron carrier?

The presence of an isoprenoid tail Signup and view all the answers

Which of the following is NOT a function of the iron-sulfur centers in the electron transport chain?

Provide a binding site for copper ions Signup and view all the answers

Which of the following complexes in the electron transport chain directly links the TCA cycle to electron transport?

Complex II (succinate-coenzyme Q reductase) Signup and view all the answers

What is the primary function of the heme prosthetic group in cytochrome c oxidase (Complex IV)?

To act as the final electron acceptor, transferring electrons to oxygen Signup and view all the answers