18.4 oxidative phosphorylation

where are the electron transport chains present

in the membranes of the cristae of the mitochondria

why is oxygen important for aerobic respiration

oxygen acts as the final electron acceptor. without oxygen the electron transport chain cannot continue as the electrons have nowhere to go. Without oxygen accepting the electrons the reduced co enzymes NADH and FADH cannot be oxidised to regenerate NAD and FAD, so they cannot be used in further hydrogen transport

chemiosmotic theory

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

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

• the energy of the hydrogens flowing down their concentration gradient is harnessed resulting in the phosphorylation of ADP into ATP by ATP synthase

an outline of oxidative phosphorylation 

• hydrogen atoms are donated by reduced NAD and reduced FAD from the krebs cycle

• hydrogen atoms split into hydrogen ions and electrons

• the high energy electrons enter the electron transport chain and release energy as they move through the electron transport chain

• the released energy is used to transport protons across the inner mitochondrial membrane from the matrix into the intermembrane space

• a concentration gradient of protons is established between the intermembrane space and the matrix

• the protons returns to the matrix via facilitated diffusion through the channel protein ATP synthase

• the movement of protons down their concentration gradient provides energy from ATP synthesis

• oxygen acts as the final electron acceptor and combines with protons and electrons at the end to form water

the electron transport chain

• made up of a series of membrane proteins/electron carriers

• they are positioned close together which allows the electrons to pass from carrier to carrier

• the inner membrane of the mitochondria is impermeable to hydrpgen ions so these electron carriers are required to pump the protons across the membrane to establish the concentration gradient