Oxidative Phosphorylation

Question 1

What happens when you go through the TCA cycle

Answer 1

Protons are pumped into the inner mitochondrial space and ATP is pumped into matrix

This forms a proton gradient, which creates energy due to the membrane potential (charge difference) and the pH gradient (proton concentration diffence)

Protons flow back into the matrix via ATP synthase (Fo-F1 ATPase) by converting ADP to ATP

For each NADH= 2.5 ATP is made, FADH2= 1.5 ATP

Question 2

Chemiostatic Theory

Answer 2

The ETC creates a proton gradient that provides the energy for ATP to be synthesized from ADP

pH in IMS is 1.4 units lower than matrix which creates an energy for 5.2 kcal/mol protons
for each NADH thats oxidized 10 protons are pumped in

The theory shows that almost all of the energy is captured by proton gradient

Question 3

Mechanism of ATP synthesis

Answer 3

ATP synthase is imbedded in the mitochondrial membrane with its Fo subunit in the membrane and an F1 subunit is in the matrix side. As H flows into the matrix (and made into H20) through the synthase, ATP is formed in the matrix side

As the H flows through, the gamma subunit of synthase rotates, which causes a conformational change of the 3 alpha beta subunit pairs, the active site is between the alpha and betas (catalytic subunit)

L (loose) binds ADP
T (tight) makes ATP
O (open) releases ATP

This all requires 9 H, and makes 3 ATP

If ADP levels are low and all the subunits are not filled, it will not make ATP

Question 4

Uncoupling agents

Answer 4

Increase the permeability of membrane, causing a decrease in the proton gradient and an increase in O2 consumption
ATP synthesis stops, but electron transport continues, it produces lots of heat

24 DNP is used for weight loss, asprin overdose, thermogenin in brown fat, antibiotics

Physiological uncoupling: brown fat (BAT) in newborns and hibernating animals produces heat via thermogenin (UCP1) on the inner membrane (there is a small amount of uncoupling ANT)

It allows protons to reenter the matrix without making ATP and the energy is released as nonshivering heat (Low RCI)

Question 5

Respiratory control

Answer 5

in healthy mitochondria ETC and oxidative phosphorylation are tightly coupled but not directly)
Electron flow pumps the expected number of protons into the IMS and those protons do not leak back into the matrix unless to make ATP

If the mito functions in this way (properly) its said to have a high Respiratory control index/ ratio (RCI RCR)

RCI/R is measured by O2 consumption

it tells you how tightly coupled ETC and oxidative phosphorylation

Question 6

P/O ratio

Answer 6

phosphorylation (ATP formation) / atoms of O2 consumed)

Each ATP made requires 3 H to be translocated, 1 H required for translocase to pump ATP out and ADP in mito

Net 1 ATP requires 4 H

Question 7

Why is uncoupling important

Answer 7

1. metabolic regulation
2. limits ROS in mito
3. lab tests (PET)
4. obesity