Chapter 21 Proton-Motive Force

Flashcards from Biochemistry II Lecture Notes

What powers ATP synthesis in mitochondria?

Proton-motive force (proton gradient)

What two gradients make up the proton-motive force?

Chemical gradient (ΔpH) and charge gradient (ΔΨ)

How many H+ are needed for synthesis of 1 ATP?

3–4 (Typically 4)

What is the role of ATP synthase dimers and oligomers?

They contribute to the formation of cristae in mitochondria.

What are the two components of ATP synthase?

F1 (catalytic unit) and F0 (proton channel)

Where are the active sites located on ATP synthase?

On the three β subunits of the F1 component

What connects the F1 and F0 components of ATP synthase?

The γ subunit

What three conformations can the catalytic β subunits of the F1 component exist in?

O (open), L (loose), and T (tight)

What does the O (open) form of the β subunit allow?

Nucleotides can bind to or be released from the β subunit.

What is trapped in the β subunit when it is in the L (loose) form?

Nucleotides

What occurs in the T (tight) form of the β subunit?

ATP is synthesized from ADP and Pi.

What does Interconversion of the three β subunits require?

Rotation of the γ subunit

What powers the movement of the γ subunit?

Rotation of the c ring

Where does proton flow occur in ATP synthase?

Through the F0 component

Where do protons enter the half-channel in subunit a?

The intermembrane space

Where do protons leave the c subunit?

Towards the matrix half channel

What determines the number of protons required to synthesize a molecule of ATP?

The number of c rings

What is the most efficient vertebrate ATP synthase made of?

Consist of eight subunits c rings

What purpose do shuttles achieve in the mitochondria?

Allow Electrons from Cytoplasmic NADH Enter Mitochondria

What shuttle do muscle cells use?

Glycerol phosphate shuttle

What shuttle do heart and liver cells use?

Malate–aspartate shuttle

What does the ATP–ADP translocase primarily enable?

The exchange of cytoplasmic ADP for mitochondrial ATP

Where does ADP need to enter for ATP to leave?

Mitochondria

What is the name of the large complex that includes ATP–ADP translocase, the phosphate carrier, and the ATP synthase?

The ATP synthasome

How many molecules of ATP are formed through substrate-level phosphorylation?

Four ATP molecules

What ultimately determines the rate of oxidative phosphorylation?

The need for ATP

What is the regulation of oxidative phosphorylation by ADP called?

Acceptor or respiratory control

What does Inhibitory factor 1 (IF1) inhibit?

ATP synthase

What is nonshivering thermogenesis?

Electron transport is uncoupled from ATP synthesis, and heat is generated.

What does uncoupling protein 1 (UCP-1) generate?

Heat by permitting the influx of protons into the mitochondria without the synthesis of ATP.