CHEMIOSMOTIC THEORY
Peter Dennis Mitchell, was a British
biochemist who was awarded the 1978
Nobel Prize for Chemistry for his discovery
of the chemiosmotic mechanism of ATP
synthesis.
Chemiosmotic Theory: coupling of ATP
synthesis to respiration is indirect, via a H+
electrochemical gradient
Chemiosmosis
Definition
• Ions move by diffusion across a
semi-permeable
membrane
(from high concentration to low
concentration).
• During chemiosmosis, ions
move down an electrochemical
gradient, which is a gradient of
electrochemical potential (a
form of potential energy).
• Ions move to balance out the
electric charge across a
membrane.
Chemiosmosis
Chemiosmotic Theory
• The transport of protons from
matrix to intermembrane space is
accompanied by the generation of a
proton
gradient
across
the
membrane.
• Protons
(H+)
accumulate
intermembrane space creating an
electrochemical
potential
difference, proton gradient or
electrochemical gradient.
• This proton motive force (PMF)
drives the synthesis of ATP by ATP
synthase complex.