electron transport chain

where does the electron transport chain take place

• inner mitochondrial membrane

what is the current model for oxidative phosphorylation

• chemiosmotic theory

what does the chemiosmotic theory state

• energy from electrons passed through a chain of proteins in the membrane is used to pump proton against their concentration gradient and into the intermembrane space

• hydrogen then allowed to flow by facilitated diffusion through a channel in ATP synthase into the matrix

1st step in electron traansport chain

• hydrogen atoms are donated by NADH from krebs cycle

• hydrogen atom splits into 2 protons (H+ ions) and 2 electrons

• the electrons are accepted by the first electron acceptor carrier within the electron transport chain

2nd stage of electron transport chain

• the electrons are passed from carrier to carrier

• as they are moved energy is released which is used by coenzymes (complexes I,II and IV) to pump protons from the matrix into the intermembrane space

• before the 2nd electron carrier, FADH2 splits into FAD and 2H+ ions and 2electrons

• H+ ions are NOT able to be pumped by complex II

3rd stage of ETC

• the electrons released from the reduced FAD enter the electron transport chain at comple II

• they are passed along the carriers and eventually combine with O2 + H+ to make water

4th stage of ETC

• electrons have passed along to complex IV

• finally the electrons combine with hydrogen ions and oxygen to form WATER

• oxygen is the final electron acceptor

• 2 electrons from complex IV bond with 4H+ ions and an O2 molecu.e to from 2H2O

5th stage of ETC

• protons pumped into the intermembrane space during ETC build up bc they are unable to diffuse through the lipid part of the membrane

6th stage of ETC

• protons diffuse back into the matrix through channels associated with ATP synthase enzymes

• this causes the rotation of the part of the enzyme which joins ADP + Pi to form ATP like a windmill

why do the hydrogen ions ahve to be pumped through the electron carriers

• the inner membrane is impermeable to hydrogen ions

why is oxygen so important for aerobic respiration

• oxygen is the final acceptor

• without oxygen the electron transport chain cannot continue as the electrons have nowhere to go

• without oxygen accepting electrons, the reduced coenzymes NADH and FADH2 cannot be oxidised to further regenerate NAD and FAD, so they cant be used in further hydrogen transport

etc diagram