chapter 19 biochem

Which processes primarily occur in the mitochondria in eukaryotic cells?

Pyruvate oxidation to Acetyl-CoA

Citric Acid Cycle

Beta-oxidation

Electron Transport Chain

Oxidative Phosphorylation

What is the correct order of molecules in the electron transport chain?

NADH, NADH Dehydrogenase complex (Complex I), Ubiquinone (Coenzyme Q), Cytochrome b-c1 complex (Complex III), Cytochrome c, Cytochrome oxidase complex (Complex IV), O₂ (final electron acceptor → reduced to H₂O)

Which components of the electron transport chain actively pump protons across the mitochondrial inner membrane?

Complex I, III, IV

What are the infoldings of the inner mitochondrial membrane called?

Cristae

Where in the mitochondria are the enzymes for the citric acid cycle found?

Mitochondrial matrix

Which components of the electron transport chain are entry points for electrons?

Complex I and II; they belong to the class of enzymes called oxidoreductases.

What is a flavoprotein?

A class of oxidizing enzymes containing flavin mononucleotide (FMN) or flavin adenine dinucleotide (FAD) as electron acceptors.

Why do electrons from FADH2 produce fewer ATP than those from NADH?

Electrons from FADH2 enter the ETC at a lower energy level (Complex II), bypassing Complex I and resulting in fewer protons pumped across the membrane.

What is the function of ubiquinone (coenzyme Q) in the electron transport chain?

It acts as a cofactor for Complexes I, II, and III in the electron transport chain.

Which class of electron carriers use a heme group for temporary storage of electrons?

Heme proteins

How are iron-sulfur centers used in the electron transport chain?

They are used as electron carriers in Complexes I, II, and III.

What is the input for Complex I in the electron transport chain?

NADH + H⁺ from the TCA cycle.

What is the output of Complex I?

NAD⁺ regenerated; CoQH₂ carries electrons to Complex III.

What is the input for Complex II?

FADH₂ from the TCA cycle (succinate → fumarate).

What is the output of Complex II?

CoQH₂ enters the pool for Complex III.

What does Complex III do?

Carries electrons from reduced ubiquinone to cytochrome c.

What is the role of cytochrome c?

It serves as a mobile electron shuttle between Complex III and Complex IV.

What is the input for Complex IV?

Electrons from cytochrome c.

What does Complex IV transfer electrons to?

O₂

What is Complex IV also known as?

Cytochrome oxidase

What does Complex IV do in the electron transport chain?

Transfers electrons from cytochrome c to O2

What is the output of Complex IV?

Water; O₂ is the final electron acceptor

How many protons are pumped by Complex IV per pair of electrons?

2 H⁺

Which component of the ETC participates directly in the reactions of the citric acid cycle?

Complex II

What is the role of Complex IV in the ETC?

Responsible for passing electrons to the final electron acceptor

What is a respirasome?

A supercomplex formed by Complexes I, III, and IV

Which component of the ETC typically remains free-floating?

Complex II-

How does the proton-motive force store energy in mitochondria?

By pumping protons out of the matrix to create a gradient

What are the two components of the proton-motive force?

Chemical potential energy and electrical potential energy

What are reactive oxygen species (ROS)?

Highly reactive products of the partial reduction of O2

How does superoxide dismutase protect cells from ROS?

Converts ROS into harmless water

What provides the energy for the FoF1 ATP synthase?

A proton gradient (proton-motive force)

Why is FoF1 ATP synthase considered Complex V of the ETC?

It is the fifth and final large protein complex in oxidative phosphorylation

What is the function of the A3β3 hexamer in FoF1 ATP synthase?

Contains catalytic sites for ATP synthesis

What does the γ-subunit of FoF1 ATP synthase do?

Acts as a central stalk that rotates inside the A3β3 hexamer

What is the role of the c-ring in FoF1 ATP synthase?

Essential for rotary catalysis

What happens in the β-ADP state of the A3β3 hexamer?

Binds ADP + Pi loosely

What occurs in the β-ATP state of the A3β3 hexamer?

Catalyzes the conversion of ADP + Pi to ATP

What is the β-Empty state of the A3β3 hexamer?

Releases ATP and is ready to accept new substrates

How many ATP molecules can be produced per NADH electron donor?

2.5 ATP

How does the malate-aspartate shuttle work?

Converts oxaloacetate into malate using NADH, then regenerates NADH in the mitochondria

What is an advantage of the glycerol 3-phosphate shuttle?

Speed in meeting high energy demands

What is a disadvantage of the glycerol 3-phosphate shuttle?

Lower ATP production efficiency compared to other shuttles

What is an uncoupling agent in relation to the ETC?

Inhibits coupling between electron transport and ATP synthesis

What happens to ATP synthase activity under hypoxia?

ATP synthesis is reduced

What is the mechanism of the small protein inhibitor IF1 under hypoxia?

Binds due to collapse in mitochondrial membrane potential, leading to acidification of the matrix