Chemiosmotic Process

Presented By_ To_

Sanjeeb Limbu(14305019) Dr.S.Kannan Sir

M.Tech.-Nanoscience & Technology Assistant Professor

(FIRST YEAR) (CNST)

PONDICHERRY UNIVERSITY

PONDICHERRY UNIVERSITY

Chemiosmosis:

Chemiosmosis is the movement of ions across a selectively permeable

membrane, down their electrochemical gradient. More specifically, it

relates to the generation of ATP by the movement of hydrogen ions across a

membrane during cellular respiration or photosynthesis.

Hydrogen ions (protons) will diffuse from an area of high proton

concentration to an area of lower proton concentration, and

an electrochemical concentration gradient of protons across a membrane

can be harnessed to make ATP. This process is related to osmosis, the

diffusion of water across a membrane, which is why it is

called chemiosmosis.

ATP synthase is the enzyme that makes ATP by chemiosmosis. It allows

protons to pass through the membrane and uses the kinetic

energy to phosphorylate ADP, making ATP. The generation of ATP by

chemiosmosis occurs in chloroplasts and mitochondria as well as in

most bacteria and archaea .

PONDICHERRY UNIVERSITY

PONDICHERRY UNIVERSITY

The Chemiosmotic Theory: Peter D. Mitchell proposed the chemiosmotic hypothesis in 1961.

The theory suggests essentially that most ATP synthesis in respiring cells comes from

the electrochemical gradient across the inner membranes of mitochondria by using the

energy of NADH and FADH2 formed from the breaking down of energy-rich

molecules such as glucose.

The carriers pass electrons to the electron transport chain (ETC) in the inner

mitochondrial membrane, which in turn pass them to other proteins in the ETC.

The energy available in the electrons is used to pump protons from the matrix across

the inner mitochondrial membrane, storing energy in the form of a

transmembrane electrochemical gradient .

The protons move back across the inner membrane through the enzyme ATP synthase

. The flow of protons back into the matrix of the mitochondrion via ATP synthase

provides enough energy for ADP to combine with inorganic phosphate to form ATP.

The electrons and protons at the last pump in the ETC are taken up by oxygen to

form water.

PONDICHERRY UNIVERSITY

As electrons are passed down the chain, protons are pumped across the membrane

(between the inner membrane and outer membrane of the thylakoids).This results in a

pH and electric gradient. The protons move back into the matrix through a pore

created by ATP synthetase allowing the enzyme to make ATP at the expense of this

gradient.

PONDICHERRY UNIVERSITY

PONDICHERRY UNIVERSITY

The mitochondrial electron-transport chain are grouped into three large

respiratory enzyme complexes, each containing multiple individual proteins.

Each complex contains metal ions that form a pathway

for the passage of electrons through the

complexes.

PONDICHERRY UNIVERSITY

Chemiosmotic Coupling: Once called the chemiosmotic hypothesis. chemi from making ATP, osmotic because of crossing the membrane. Now known as chemiosmotic coupling

PONDICHERRY UNIVERSITY

14_07_Mito_catalyze.jpg Chemiosmotic theory (Paul Mitchell, 1960’s):

Coupling of electron transfer, proton pumping and ATP synthesis

PONDICHERRY UNIVERSITY

PONDICHERRY UNIVERSITY