Ch. 21 Proton Motive Force

proton-motive force

proton gradient generated by the oxidation of NADH and FADH2

ATP synthase

unit that uses the proton gradient to spin and generate ATP

FI component of ATP synthase

contains active sites and protrudes into the mitochondrial matrix

FI subunits

alpha, beta, gamma

F0 component of ATP synthase

embedded in the inner mitochondrial membrane and contains proton channel

What does ATP synthase catalyze?

formation of ATP from ADP and Pi

What are ATP and ADP bound to in order to function as substrates?

Mg2+

Conformations of the beta subunits of F1

open (o), loose (l), tight (t)

open form

nucleotides can bind to or be released from the beta subunit

loose form

nucleotides are trapped in the beta subunit

tight form

ATP is synthesized from ADP and Pi but can’t be released from the enzyme

When is energy used in the beta subunits?

to release ATP, not to form it

Where does proton flow occur in ATP synthase?

through the Fo component

Subunit A

has a channel that opens to the intermembrane space and another to the matrix

Where does the F0 pump protons?

from the intermembrane to the matrix

What powers the rotation of the c ring?

the force of the proton gradient created by subunit A

What does the rotation of the c ring cause?

the movement of the gamma subunit, causing the conformation of the beta subunits to change

How many ATP does 1 NADH produce?

2.5 ATP

How many ATP does 1 FADH2 produce?

1.5 ATP

How many H+ does each ATP need?

3.3 H+

glycerol 3-phosphate shuttle

transfers electrons from cytosolic NADH into the mitochondria by converting them into FADH₂ at the inner membrane, which then donates electrons to CoQ

malate-aspartate shuttle

Glutamate and α‑ketoglutarate convert oxaloacetate ↔ aspartate on each side of the membrane, moving electrons into the matrix; in heart and liver cells

ATP-ADP Translocase

swaps ATP out for ADP in, using the membrane potential to keep ATP synthase supplied with substrate

What does ATP-ADP translocase use for energy?

proton-motive force, the difference in charges

How many molecules of ATP is yielded from the complete oxidation of glucose?

30 ATP

How much ATP is produced by glucose in the heart / liver?

32 ATP

How much glucose is produced by glucose in the muscles?

30 ATP

glycolysis net reaction

Glucose + 2 Pi + 2 ADP + 2 NAD⁺ —> 2 pyruvate + 2 ATP + 2 NADH + 2 H + 2 H2O

pyruvate dehydrogenase net reaction

pyruvate + CoA + NAD⁺ —> acetyl CoA + CO2 + NADH + H⁺

CAC net reaction

Acetyl CoA + 3 NAD⁺ + FAD + ADP + Pi + 2 H2O —> 2 CO2 + 3 NADH + FADH2 + ATP + 2 H⁺ + CoA

acceptor / respiratory control

regulation of oxidative phosphorylation by ADP

When do electrons flow through the ETC?

if ADP is available to be converted to ATP

When is ADP low and ATP high?

when there is sufficient energy

When is ADP high and ATP is low?

when there is low energy

How is oxidative phosphorylation inihibited?

inhibiting the ETC to prevent forming the proton motive force or by uncouplers

Uncouplers

carry protons across the inner mitochondrial membrane, proton gradient can’t form so ATP synthesis is inhibited

2,4-dinitrophenol

example of an uncoupler