ATP synthesis

chemiosmotic theory

energy stored in ion gradient across a membrane

• like a battery

what is the short term energy stored in the membrane potential used for?

work

• transport ions/solutes against their gradients

• rotational catalysis→ ATP synthase

how many ATP per ATP synthase spin?

3 ATP

how many protons does it take to make an ATP?

depends on how many protons are needed to make ATP synthase spin

about how many protons to make 3 ATP?

10-16 H+

components of proton gradient provided energy (2)

1. pH gradient (based off of H+)

2. electric potential (based off of charge)

what happens if too many protons outside the membrane?

they float away and move around in water→ decreasing pH → proteins degrading

proton motive force (\Delta p )

mV

• force that is pulling protons down their gradient

if the proton-motive force is high…

it takes more force to pump the protons out

how to generate a \Delta p (4)

1. pump H+ out

2. fermentation → pH gradient

3. pump out protein → bring in ion (exchange)

4. bring electrons in

if H+ stay on/at membrane…

electrical potential develops

is H+ move into solution

change in pH develops

what do iodophors/uncouplers do?

increase membrane permeability to one or many ions

• can selectively change change in electron portential or pH

what does eliminating \Delta p do?

kills atp synthesis/coupled transport

• unused H+ leaves as heat

what does DNP and UCP1 do?

takes more proton motor force to make ATP → takes more fuel

• lose weight

• too much leads to inability to make ATP or too much internal heat made→ death

what are the good things ionophores/uncouplers do?

stimulate electron/respiration transport

using \Delta p to do symport in what way?

• protons moving down gradient can pull things into cell

  • 1 proton moving a solute against it gradient → 100-1000x more solute inside cell then outside

antiports that use \Delta p to do work

• exchange ions (H+ in→ ion out)

• drives ADP in/ ATP out exchange across inner membrane

ATP synthase

use proton motive force to combine ADP and Pi→ ATP

F1 particle of ATP synthase

catalytic portion

• 3a,2\beta,1\gamma,1\delta,1\epsilon subunits

F0 base of ATP synthase

embedded in inner membrane

• 8-18 c subunits (grab proton)

F0 particle of ATP synthase

hold F1 in place and allows protons to move from intermembrane space to the mitochondrial matrix

where are the active sites in ATP synthase?

in each of the 3 \beta subunits

• near \alpha \beta interface

what are the 3 conformations of the active sites in ATP synthase?

each active site is in a different conformation at once

1. open- atp is released and adp and pi come in

2. loose- bound to adp and Pi

3. tight- hold ADP and Pi rly close so they have → ATP

where is the rate limiting step of the 3 different active sites conformation in ATP synthase?

tight→ open

what causes tight→ loose confirmation

getting jammed by the gamma subunit

rotational catalysis

rotation of the gamma subunit jabbing different subunits in the back

subunit a

has a channel to allow protons to come in and be fed into empty holes of subunit c→ causing it to spin

• another channel to accept protons back from subunit c and transfer it to mito matrix

how do P/O ratios vary

1. types of electron transporters

2. number of c subunits → how many protons it takes to do a full rotation

how many ATP/ electron transporters when electron transport goes to complex 1

2.5 ATP/ NADH

how many ATP/ electron transporters when electron transport goes to complex 2?

1.5 ATP/FADH2

adenine nucleotide translocase

brings ADP to inner membrane space

send ATP out

• ATP attracted to intermembrane space because of pos charge

phosphate transolcase

symporter

• brings in H2PO4- and one H+ into matrix

ATP sythasome

a complex of ATP synthase both transolactors (phosphate transolcase and adenine nucleotide transolcase)

what happens when we block e- transfer?

AT synthesis stops because we need \Delta p to drive ATP synthase

what can we do if ATP synthesis is blocked?

add an uncoupler→ allows electron transporters number to continue and continue to help the \Delta p

• gets rid of gumming up