Oxidative Phosphorylation and ATP Synthesis

Flashcards about Oxidative Phosphorylation and ATP Synthesis

Why is NADH not directly transported across the inner mitochondrial membrane?

There is no NADH transporter on the inner mitochondrial membrane.

What is the main purpose of the malate-aspartate shuttle?

To transfer electrons and protons from cytoplasmic NADH to NAD+ in the mitochondrial matrix.

How many ATP are produced per NADH when the malate-aspartate shuttle is used?

3 ATP per NADH

Where does the glycerol-phosphate shuttle primarily function?

Metabolically active tissues like neurons and muscle.

What is the net ATP production from glycolysis, and what else is produced?

Net 2 ATP + 2 NADH

What happens to the electrons passed from NADH and FADH2 to oxygen?

They are transferred from one carrier to the next in the ETC that has a significantly higher affinity for electrons than the previous carrier ,resulting in the formation of water.

What two gradients form the electrochemical gradient?

The electrical gradient and the chemical gradient.

What is the final electron acceptor in the electron transport chain?

Molecular oxygen (O2)

What is the role of Complex I (NADH ubiquinone reductase/ NADH-Q reductase)?

It oxidizes NADH and transfers 2 electrons to ubiquinone, transferring ~4 protons across the inner mitochondrial membrane.

What is ubiquinol (QH2)?

Reduced ubiquinone, a mobile carrier of electrons throughout the mitochondrial membrane.

What is the function of Complex III (Q-cytochrome-c oxidoreductase)?

Receives electrons from QH2 and transfers from to cytochrome-c (transferring electrons from one mobile carrier to another). 4 protons (2 from QH2 and 2 from the matrix) are transferred into the intermembranous space (IMS).

What is the role of Complex IV (cytochrome oxidase)?

Transfers electrons from cytochrome-c to oxygen, which is coupled by the transfer of 2 protons, producing H2O.

How many protons are transferred to the intermembranous space (IMS) per NADH oxidized?

Approximately 10 protons.

How many ATPs are produced from FADH2?

Approximately 2 ATPs.

Roughly how many H+ are required per ATP synthesised in the ATP synthase channel?

Roughly 3 H+ are required per ATP.

How does the ATP synthase rotor work to synthesize ATP?

The return of H+ causes rotation of the ATP synthase spindle (rotor), leading to conformational changes in the head group subunits (stator) and generates a proton motor force, that drives ATP synthesis from ADP and Pi.

Where does ATP synthesis occur?

Mitochondrial matrix

How are ATP and ADP transported across the inner mitochondrial membrane?

By an antiporter, driven by the charge across the membrane.

Why does electron transport stop if there is no demand for energy?

ADP levels would be low as ATP does not need to be hydrolysed, halting H+ return to the matrix, thus the proton gradient opposes electron transport. H+ can’t return to the matrix and the proton gradient will be matched by the oxidation of NADH causing the electron transport chain to stop

What is the role of ADP in regulating ATP synthesis?

Rising ADP levels signal a cytoplasmic demand for energy which allows ADP to enter the matrix, be phosphorylated by ATP synthase, and reduce the proton motive force, restarting the electron transport chain to renew the proton motive force.

What is the role of QH2 (Ubiquinone)

To deliver electrons to Complex II. The transfer of one electron results in the movement of 2 protons into the IMS