Respiration A levels

• ATP is soluble - It can transport chemical energy to all energy-consuming processes in the cell. . • Hydrolysis of ATP releases energy and requires water . • Phosphorylation of ADP forms ATP - ADP is phosphorylated with inorganic Pi by the enzyme ATP synthase . This supports ATP’s role as a universal energy carrier.

• Glycolysis - O2 not needed - Occurs in the cytoplasm - glucose (6C) is oxidised to produce 2 molecules of pyruvate (3C) . • Link Reaction - O2 needed but not directly involved - Occurs in mitochondrial matrix of a euk cell OR the cytosol of a prokaryote - Pyruvate is oxidised to acetyl-CoA . • Krebs Cycle - O2 needed but not directly involved - Occurs in mitochondrial matrix of an euk cell OR the cytosol of prokaryotes - Acetyl-CoA is further oxidised via a series of reactions . • Oxidative phosphorylation - O2 directly involved - Occurs in Inner mitochondrial membrane of euk cell OR CSM of prokaryotes - electrons released via oxidation in the first 3 stages are transported along an electron transport chain to release large amts of energy

• Energy investment phase or Preparatory phase . • Energy pay-off phase

• Activation of glucose - to make it more chemically reactive - Glucose is phosphorylated into glucose-6-phosphate by hexokinase using** ATP** . • Isomerisation - Glucose is isomerised to fructose-6-phosphate . • Phosphorylation of fructose-6-phosphate using ATP - Fructose-6-phosphate is phosphorylated to fructose-1, 6-** bis**phosphate by _phosphofructokinase using ATP. . • Cleavage of fructose-1, 6-bisphosphate - into 2 triose phosphates - which are di hydroxy acetone phosphate and glycer aldehyde-3- phosphate . • Isomerisation - Isomerisation of -dihydroxy acetone phosphate_ into glycer aldehyde-3- phosphate - The final prdts are 2 molecules of glycer aldehyde-3-phosphate

• Subsequent conversion of each gylceraldehyde (GALP) molecule to pyruvate via multiple steps. . the multiple steps: - generate 2 ATP via substrate level phosphorylation .AND - GALP releases protons and electrons via dehydrogenation which are transferred to 1 oxidised NAD to form 1 reduced NAD . Since 2 molec of GALP is formed from 1 glucose, 2 pyruvate, 4 ATP and 2 reduced NAD can be produced from 1 glucose

• Activation (has enzyme and ATP) • isomerisation • Phosphorylation (has enzyme and ATP) • cleavage • isomerisation

Nicotinamide adenine dinulceotide It is a co-enzyme and a proton/electron carrier

Flavin adenine dinucleotide. It is a co-enzyme and a proton/electron carrier.

Since 2 molec of GALP is formed from 1 glucose, 2 pyruvate, 4 ATP (net 2 ATP) and 2 reduced NAD can be produced from 1 glucose after glycolysis

A mode of ATP synthesis where an enzyme transfers a phosphate group from a substrate molecule to ADP. . - Occurs during glycolysis and Krebs cycle. - Compared to oxidation phosphorylation, only a small amt of ATP is genrated here

• In presence of O2, Pyruvate enters the mitochondrion via active transport of a transport protein. . - Pyruvate undergoes oxidative decarboxylation catalysed by dehydrogenase. . • Pyruvate is Decarboxylated - carboxyl grp of pyruvate is removed - CO2 is released - 2C molecule produced. . • **_Oxidation / Dehydrogenation - resulting 2C molecule undergoes oxidation via dehydrogenation - Protons and e- from 2C moelcule are transferred to oxidised NAD, converting it to reduced NAD. - Acetate is produced. . • Additon of Coenzyme A - Coenzyme A is attached to acetate to form acetyl CoA. . Prdts formed from link reaction per glucose (2 GALP / 2 pyruvate) 2 acetyl CoA, 2 CO2, 2 Reduced NAD

per glucose / 2 GALP / 2 Pyruvate: - 2 Acetyl CoA - 2 CO2 - 2 reduced NAD

• Acetyl-CoA is attached to ox-alo-acetate to form citrate. - Citrate is isomerised into isocitrate. . • Isocitrate undergoes oxidative phosphorylation & reduces NAH to reduced NAD. - Isocitrate also decarboxylated & releases 1 CO2 while reducing NAD into NADH, - forming a 5C carbon. - Resulting mol is decarboxylated again to form a 4C compound. - NAD is reduced to NADH again. . • Substrate level phosphorylation - Inorganic phosphate is transferred from 4C compound to ADP to form ATP. . • FAD reduced to FADH2 - while 4C compound is oxidised. . • 1 ATP is produced via substrate level phosphorylation . • Oxaloacetate regeneration - NAD reduced to NADH - substrate from prev step is oxidised, - regenerating oxaloacetate

2 times bcuz 2 acetyle-CoAs were produced to react w oxaloacetate.

• Electron transport chain . • Chemiosmosis

• a collection of electron carriers embedded in the inner mito matrix. . • extensively folded mito (cristae) increase SA to vol ratio, more space for more copies. . • electron carriers arranged in decreasing levels of free energy

• Reduced NAD and FAD transfer high energy e- to ETC for synthesis of ATP. . -Electrons are passed along the ETC from one e- carrier to the next, each w lower a energy level than the previous one. . • e- carriers alternate btwn oxidised and reduced as they accept and donate e-. . • the last e- carrier passes the e- to oxygen. • O2 acts as the final H+ & e- acceptor to become water in a rxn catalysed by cytochrome oxidase. . • **Oxidised NAD and FAD are regenerated** in this process

• occurs alongside ETC for ATP synthesis. • as e- are passed from 1 e- carrier to the next, energy released is used to pump H+ from the matrix of the mito into the intermembrane space (outisde mito). . • High [H+] in intermembrane space creates a steep electrochemical proton gradient • The proton motive force generated powers chemiosomosis. . • Stalked particles each containing ATP synthase are embedded on the inner mito membrane. • H+ diffuse through the stalked particles, down the electrochemical proton grad, back into the matrix. . • This provides enough energy to synthesise ATP by phosphorylation of ADP w inorganic phosphate

• Glycolysis can still occur in the cytosol, without oxygen to yield pyruvate, • generating a small yield of 2 ATP molecules per glucose • via SLP • and NADH is also produced . • In lactate fermentation • pyruvate gets reduced to lactate • NADH is oxidized to NAD, • catalysed by lactate dehydrogenase • to regenerate NAD for use in glycolysis . • allow glycolysis to continue generating ATP in the absence of O2

• Glycolysis can still occur in the cytosol, without oxygen to yield pyruvate, • generating a small yield of 2 ATP molecules per glucose • via SLP . • In alcoholic fermentation • pyruvate gets decarboxylated to release CO2 • _pyruvate gets reduced to ethanol • while NADH is oxidized to NAD, • catalysed by alcohol dehydrogenase • to regenerate NAD for use in glycolysis . • allow glycolysis to continue generating ATP in the absence of O2

• 2 ATPs are used in the energy investment phase to phosphorylate glucose, forming fructose-1,6-bisphosphate which is cleaved to form 2 glyceraldehyde-3-phosphates (GALP) . Energy pay off phase • 2 G3Ps are then oxidised by dehydrogenation while 2 NAD is reduced to 2 NADH. • Substrate level phosphorylation occurs where a phosphate group from the substrate is transferred to each of the 4 ADPs to form 4 ATPs, catalysed by an enzyme. . • Eventually forming 2 pyruvates (3C) , • net gain of 2 ATP and 2 NADH in the cytosol.

• NAD+ and FAD are coenzymes for dehydrogenase rxns during glycolysis, link rxn and Krebs . . NAD+ and FAD+ are also mobile electron carriers • Upon getting reduced in glycolysis, link reaction and the Krebs cycle , NADH and FADH2 carries electrons to the e - carriers in the ETC . • In oxidative phosphorylation, NADH and FADH 2 are oxidised to regenerate NAD and FAD - This releases the e- into the ETC to be captured by O2 at the end of the ETC . • H+ released from the oxidation are pumped into the intermembrane space to establish a electrochemical proton gradient for chemiosmosis - for ATP synthesis

((aerobic resp produces net 32 ATP per glucose while anaerobic resp produces net 2 ATP per glucose)) . Why no OP - in anaerobic resp, - w/o O2 as the final e- acceptor in oxidative phosphorylation, - NADH and FADH2 cannot be oxidised - to regenerate NAD+ and FAD - to release e-s down the ETC • w/o ETC, there is no energy released to pump H+ from matrix to IMS • NO electrochemical proton gradient established . • NO chemiosmosis • H+ cannot diffuse from high conc in the IMS to a lower conc in the matrix through ATP synthase • ATP synthase CANNOT phosphorylate ADP to ATP • hence NO ATP from OXIDATIVE PHOSPHORYLATION . Why no Krebs • NO oxidation of NADH & FADH2 to regenerate NAD & FAD • NO NAD and FAD for link rxn & Kreb

• acts as the final e- acceptor at the end of the ETC during oxidative phosphorylation • combines with e- and H+ to form H2O (in a rxn catalysed by cytochrome oxidase) . • O2 removes e- from the ETC • AND oxidises the ETC • so NADH and FADH2 can continue to donate e- • for OP to continue producing ATP . • This ALSO allows NAD+ and FAD to be regenerated so they transport more e-s and H+ (from__) for respiration to continue