Respiration.pdf

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  Aerobic Respiration...

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  Aerobic Respiration C6H12O6 + 6O2 + 6H2O 6CO2 + 12H2O + energy (glucose) (ATP) 1 mole glucose 36 ATP  Efficiency of Aerobic Respiration ADP-P bond releases -7.6 kcal/mol ATP when bond is broken Theoretical energy yield from burning 1mol glucose in a calorimeter = -686 kcal/mol Practical yield from burning 1mol of glucose in the cell with oxygen = 36ATP ▪ 36 ATP X -7.6 kcal/mol = -274 kcal/mol glucose ▪ 274/686 kcal/mol X 100 = 40% efficiency  Efficiency of Anaerobic Respiration ADP-P bond releases -7.6 kcal/mol ATPwhen bond is broken Theoretical energy yield from burning 1mol glucose in a calorimeter = -686 kcal/mol Practical yield from burning 1mol of glucose in the cell without oxygen = 2 ATP ▪ 2 ATP X -7.6 kcal/mol = -15.2 kcal/mol glucose ▪ 15.2/686 kcal/mol X 100 = 2.2% efficiency  3 Stages of Respiration Glycolysis ▪ 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  Spherical to oval Mitochondria ▪ about 1 micron diameter ▪ # mito./cell increases with demand for respiration; 300-1000/root tip cell Double-membrane bound ▪ outer smooth ▪ inner folds forming cristae controls movement in/out site of electron transport cristae matrix  Glycolysis Occurs in all living organisms Only stage which can occur without oxygen Oldest stage of respiration ▪ operated for billions of years in anaerobic organisms Converts glucose to 2 pyruvates in cytosol ▪ with O2 goes on to TCA cycle ▪ without O2 pyruvate is converted to lactate or ethanol (fermentation) Yields 2ATP/mole glucose in the absence of O2  Glycolysis Glucose (6C) 2 Pyruvate (3C) CO2 -O2 -O2 +O2 Ethanol Lactate TCA Cycle  Matrix ADP + Pi ATP H+ + NADH NAD+ + 2H+ + ½ O2 H2O 2H+ F1 2 –– I e Q III IV Fo ++ cyt 3H+ 4H+ 4H+ 2H+ c Intermembrane Space The Chemiosmotic Theory of oxidative phosphorylation, for which Peter Mitchell received the Nobel prize: Coupling of ATP synthesis to respiration is indirect, via a H+ electrochemical gradient.  Chemiosmotic theory proposed by Peter Mitchell The transport of protons from matrix to intermembrane space is accompanied by the generation of a proton gradient across the membrane. Protons (H+) accumulate in the 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. IMM- Inner mitochondrial membrane IMS- Inter membrane space Peter mitchel OMM- outer mitochondrial membrane H+ H+ H+ H+ H+H + 4H+ 4H+ 2H+ H+ H+ 2e- III I Iv H+ + H+ 4H+ H + H H + 4H+ H+ H+ H+ ADP+Pi H+ + H H + + 4H+ 4H++ H V H H+ H+ H+ H+ ATP HH+ + H + + H + H H + MATRIX H + HH + HHH+ ++ H+ H+ +H+ H+ H+ H+ IMM H+ Complex I, III and IV H + + H+ H + H are proton pumps H + H + IMS H + H+ OMM  Proton dependent ATP synthese ¡ ATP synthase is a protein assembly in the inner mitochondrial membrane. ¡ Uses proton gradient to make ATP ¡ Protons pumped through channel on enzyme ▫ From intermembrane space into matrix ▫ ~4 H+ / ATP NADH FADH2 10 H+ X 1 ATP = 2..5 (3) 6 H+ X 1 ATP = 4 H+ ATP 1.5 (2) ATP 4 H+ ATP synthase has two units F1 - projects into matrix -has 3 α , 3 β , gamma , delta, epsilon chains -catalyses ATP synthesis Peripheral catalytic sites are present on beta subunits. Fo - embedded in membrane - acts as channel for transport of H+  ADP + Pi ATP matrix F1 34H+ Fo intermembrane space H+ H+ H+ H+ H+ H+ H+ H +  Alternate Fates of Glucose C Not all C respired to CO2 Intermediates of respiration branch off: ▪ amino acids ▪ pentoses for cell wall structure ▪ nucleotides ▪ porphyrin biosynthesis ▪ fatty acid synthesis ▪ lignin precursors ▪ precursors for carotenoid synthesis, hormones Factors Affecting Resp. Rate [Substrate] [ATP] [Oxygen] Temperature Plant type Plant organ Plant age