Lecture 30 - ATP synthesis Flashcards
Who proposed the chemiosmotic coupling hypothesis for ATP synthesis
Peter Mitchell, in 1961
What is oxidative phosphorylation
It is the process where electron transport through the ETC is coupled with phosphorylation of ADP to ATP by ATP synthase, driven by proton gradient
Describe the chemiosmotic coupling hypothesis
The hypothesis suggest that the energy required for ATP synthesis is provided by a proton gradient by the ETC across the IMM
What is the proton motive force PMF
Its the electrochemical gradient generated by the ETC, consisting of chemical and electrical gradient, which drives ATP synthesis
What are the two components of the PMF
- Chemical gradient - due to the proton concentration differences
- Electrical gradient - due to the charge difference
How does the ETC contribute to the PMF
The ETC pumps protons from the Mitochondiral matrix to the inter membrane space, creating the proton gradient necessary for ATP synthesis
How does the ATP synthase generate ATP using the PMF
ATP synthase acts like a rotary motor, with protons flowing through the FO subunit causing rotation. The mechanical energy leads to the conformational changes in the F1 subunit, allowing it to catalyse the conversion of ADP and P into ATP
How many protons required to generate one ATP molecule
4 protons are required to generate one ATP molecule
How many protons are pumped when one NADH enters the ETC, and how much ATP is produced?
One NADH pumps 10 protons and produces approximately 2.5 ATP.
How many protons are pumped when one FADH2 enters the ETC, and how much ATP is produced?
One FADH2 pumps 6 protons and produces approximately 1.5 ATP
What are uncouplers and how do they affect the oxidative phosphorylation
Uncouplers are molecules that dissipate the proton gradient by allowing protons to flow back into the matrix without generating ATP, which leads to increased metabolism but no ATP synthesis. The ETC functions
DNP as a uncoupler
In the presence of DNP
- ETC functions
- No ATP is made
Describe an experiment that supports the chemiosmotic theory using an artificial liposome
An artificial liposome with bacteriorhodopsin (a light-induced proton pump) and ATP synthase was created. In light, bacteriorhodopsin pumped protons, and ATP was synthesized, proving the proton gradient alone drives ATP synthesis.
What happens to the energy stored in the proton gradient if uncouplers are present
The energy is released as heat, since the proton gradient is dissipated without producing ATP
What was the evidence from mitochondrial isolation experiments for the chemiosmotic hypothesis?
When mitochondria were treated with mild detergents that removed only the outer membrane, the ETC worked, but no ATP was produced, showing the need for a proton gradient across an intact membrane.
