Oxidative Phosphorylation

Question 1

What is Oxidative Phosphorylation?

Answer 1

Combination of the e- transport chain w/ ATP synthase
- Primary source of ATP in aerobic cell

Question 2

Where does ox. phosphorylation occur?

Answer 2

in the inner mitochondrial membrane

Question 2

Mitochondria; Endosymbiosis theory

Answer 2

• mito. were once ind. unicellular organisms
• taken up by cells by endosymbiosis
  Evidence: Two membranes, Mito. DNA, size/shape

Question 3

High energy e- are transferred to the ETC

Answer 3

• the TCA produces 3 NADH and 1 FADH2 for each acetyl-CoA that enters
• NADH and FADH2 are carriers of high energy e-
• these e- are passed through ETC in series of redox rxn

Question 3

The ETC

Answer 3

• greater number of H+ in intermembrane space than inner mitohcondrial membrane
• ATP created form ATP synthase not ETC

Question 4

Generation of free radicals

Answer 4

• reduction of O2 has dangerous rxns that generate reactive oxygen species
• results in diseases
• efficient enzymes convert ROS into harmless water to protect the cell

Question 5

Generation of Proton Gradient

Answer 5

Free energy released as e- are transferred down the ETC is used to pump protons at complexes into the intermembrane s[ace

Question 6

How does the proton gradient power ATP synthesis?

Answer 6

Proton pumping generates a pH and electrochemical gradient - combination of these gradients is called the proton-motive force

Question 7

Oxidative Phosphorylation

Answer 7

Production of ATP from ADP and P driven by the free energy produced by the transport of e- through the ETC

Question 7

Chemisomotic Hypothesis

Answer 7

Protons transfered to intermembrane space re-enter the mitochondrial matrix through a channel in the enzyme AtP synthase driving the synthesis of ATP

Question 8

ATP synthase

Answer 8

embedded in the inner mitochondrial membrane

Question 9

Synthesis of ATP

Answer 9

ATP synthase has three active sites that perform 3 different tasks
1- Trapping ADP + P
2- ATP synthesis
3- ATP release and ADP + P binding
- Proton motive force causes the active sites to change functions as protons flow through

Question 10

ATP synthase subunits

Answer 10

• subunits rotate 120 degrees, points to active sites
• spinning dictates active site and stimulates production of ATP

Question 10

Experimental evidence of rotation

Answer 10

• fluorescently labelled actin filament rotates in correlation to ATP synthesis

Question 10

Proton flow around C-ring powers ATP synthase

Answer 10

• glutamic acid fits into cytoplasmic half-channel allows to turn
• pressure to relieve gradient

Question 11

Proton Path

Answer 11

• Proton enters from intermembrane space
• binds Glu making it neutral
• rotates clockwise 9 steps before being released into matrix

Question 11

Regulation of rate of oxidative phosphorylation

Answer 11

• e- do not usually enter ETC without forming ATP
• increases in ADP result in increased oxidative phosphorylation
• if conc. of ADP are low, will also effect the rate of TCA
• high levels of ATP, decrease TCA
• high levels of ADP, increase TCA

Question 12

Uncoupling results in heat generation

Answer 12

• UCP-1 is a protein in the inner mitochondrial membrane
• provides alternate path for protons to return to matrix
  (bypass ATP synthase, producing heat)
• overdoes of apirin is similar, binds protons when in inter membrane space producing heat