Government Degree College Bijbehara Department of Botany Prof Burhan Ahad Semester IV Topic : Electron Transport Chain (Cellular Respiration)

Brief Introduction of Respiration Biological process whereby the energy stored in carbohydrates from PS is released in a step-wise, controlled manner. Energy released is coupled to the synthesis of ATP. ATP is essential for plant cell maintenance, growth and development

Cellular respiration a metabolic pathway of redox reactions: -oxidation – loss of electrons dehydrogenations: loss of hydrogen e-’s -reduction - gain of electrons gain on hydrogen e-’s Oxidized molecules actually loose a hydrogen atom (1 electron, 1 proton) Both the protons and electrons are used by cellular respiration to produce ATP

3 Stages of Respiration Glycolysis TCA Cycle Electron Transport Chain cytoplasm with or without oxygen present breaks glucose (6C) into 2 pyruvates (3C) TCA Cycle mitochondrial matrix only if oxygen present converts pyruvate via acetyl CoA into CO2; generates NADH and FADH2 Electron Transport Chain mitochondrial membranes = cristae transfers electrons from NADH and FADH2 to reduce O2 to H2O and generate ATP

Glycolysis Glucose (6C) 2 Pyruvate (3C) Ethanol Lactate TCA Cycle CO2 -O2 -O2 +O2 Ethanol Lactate TCA Cycle

TCA cycle

Electron Transport Chain During respiration, high energy electrons are passed along chains of molecules - Electron Transport Chains Energy is released as molecules in the electron transport chains are oxidized The energy released is used to power the production of ATP

Electron Transport System NADH and FADH2 e- H+ ATP e- H+ 4e- + 4H+ + O2 2H2O cyt. oxidase

Stage 3: Electron Transport Chain The electron transport chain (ETC) is a series of membrane-bound electron carrier molecules called cytochromes embedded in the mitochondrial inner membrane electrons from NADH and FADH2 are transferred to cytochromes of the ETC each cytochrome transfers the electrons to the next cytochrome in the chain

Stage 3: Electron Transport Chain Energy from the Electrons As the electrons are transferred, some electron energy is released with each transfer This energy is used by the cytochromes to pump protons (H+) across the membrane from the matrix to the inner membrane space

Stage 3: Electron Transport Chain Energy from the Protons Electron energy is used by the cytochromes to pump protons (H+) across the membrane from the matrix to the inner membrane space A proton gradient is established There are more protons on the

Stage 3: Electron Transport Chain The cytochromes are channel proteins and use the electron energy to pump protons (H+) across the inner mitochondrial membrane Now there are more protons on the inside of the membrane than the outside A proton gradient is established This proton gradient is potential energy that can be utilized to make more ATP’s Recall diffusion: The protons want to equalize their number on both sides of the membrane

Stage 3: Electron Transport Chain

Stage 3: Electron Transport Chain There are other channel proteins in the membrane known as ATP synthases ATP synthases provide a channel for the protons to diffuse through The rushing protons provides the energy for ATP synthase to phosphorylate ADP to ATP

Animation OF ETC

Stage 3: Electron Transport Chain In Aerobic Respiration, oxygen is the final molecule to receive the hydrogens as they are passed down the Electron Transport Chain The result is water: O2 + 4e- + 4H+ 2H2O Oxygen is reduced to water Oxygen is the Final Electron Acceptor in Aerobic Respiration