L13 - Oxidative Phosphorylation

Oxidative phosphorylation is how ___ is produced

ATP

Chemiosmotic theory: the synthesis of ATP is coupled to

electron transport, energy rich proton gradient, hydrogen ions diffuse back via the ATP synthase complex, energy from proton gradient is used to drive the conversion of ADP to ATP

Experimental design showed that we need ________ for ATP synthesis

e^- transport

Experimental design showed that uncoupling e^- transport and atp synthesis showed that electron transport can

occur without atp synthesis by dissipating the proton gradient

At equilibrium of proton gradient, there is no

ATP synthesis; Equilibrium of H⁺ and charge

By changing the proton concentration, there is a proton gradient that drives

ATP synthesis even without oxygen consumption. Potential difference drives ATP synthesis.

Less H⁺ going in than out.

ATP synthase is F_o membrane embedded in the ___________ and F1 is present in the ____

inner membrane; matrix (N)

______________ has the proton gradient

Intermembrane space (P)

F1 complex has 3 alpha and 3 beta subunits that are arranged

alternating which makes 3 dimers of alpha and betas attached to a gamma shaft

F1 is the site of

atp synthesis

ATP is synthesized at the

interface between alpha-beta dimers

Alpha-beta dimers do not rotate but they

adopt different conformations as the gamma shaft rotate

Conformational process of F1 complex

ADP + Pi enters alpha beta, gamma shaft rotates 120 degrees, causing a conformational change, ADP+Pi -> ATP, gamma shaft 120 degrees, causing a conformational change, ATP released

______ is the driving force of the rotation of the gamma shaft. Rotation is driven by proton gradient

F_o complex

F_o has a half channel on the _____ side and a half channel on the _____ side

positive; negative

F_o is made up of

an a, b, and c ring (8-15)

C subunits on F_o complex in the c ring formation will rotate as a

unit which allows protons to be released to the negative side from the positive side

C ring on F_o complex is like a

ferris wheel that carries protons; Once all spots are filled, the first H⁺ will exit on the other side of membrane (N) to allows another H⁺ from P side to enter

ADP enters the matrix by

adenine nucleotide translocase (antiporter) as ATP exits the matrix

Phosphate groups enters the matrix via the

phosphate translocase (symporter) with H+ protons

Phosphate translocase is/ is not coupled with ATP synthesis

IS NOT even though it transports H+ protons; it just needs the energy from gradient (Not ATP)

NADH created in glycolysis needs to be transported from the cytosol to

the mitochondrial matrix

NADH needs to go through electron exchange to enter the mitochondrial matrix:

Oxaloacetate -> Malate which oxidizes NADH, malate is transported to matrix by malate-akg transporter, malate -> oxaloacetate which reduces NAD+ to NADH

glycerol 3-phosphate shuttle is an alternative way of moving

reducing equivalents from the cytosol to the respiratory chain, and operates in skeletal muscles in the brain.

Glycerol 3-phosphate is not as efficient but is _____; Why?

rapid; FADH₂ is not as energy efficient as NADH

Glycerol 3-phosphate pathway

1. NADH + H⁺ from glycolysis is oxidized via cytosolic glycerol 3-phosphate dehydrogenase.

2. At the same time, it reduces Dihydroxyacetone phosphate to glycerol 3-phosphate.

3. This is then oxidized by mitochondrial glycerol 3-phosphate dehydrogenase to reduce FAD to FADH_2, which can then be transferred to Ubiquinone and then complex III in the ETC.

4. Dihydroxyacetone phosphate is recovered during oxidation.