Respiration and ATP

STRUCTURE AND FUNCTION OF ATPATP stands for ADENOSINE TRIPHOSPHATE. It is a phosphorylated nucleotide and consists of ADENINE, RIBOSE and the PHOSPHATE GROUPS. When a phosphate group is removed from ATP in a HYDROLYSIS REACTION, 30.6kJ of energy is released per mole of ATPThe energy released is used to drive biological processes in the body, collectively known as METABOLISM. Processes that require ATP include ACTIVE TRANSPORT, MUSCLE CONTRACTION, PROTEIN SYNTHESIS, endocytosis and exocytosis, DNA replication and nerve conduction.

STAGES OF RESPIRATIONAerobic Respiration consists of four stages:-GLYCOLYSIS which takes place in the CYTOPLASM-the LINK REACTION and KREB'S CYCLE which take place in the MATRIX of the mitochondria-OXIDATIVE PHOSPHORYLATIO, which takes place in the CRISTAE of the mitochondria

GYLCOLYSIS1 - PHOSPHORYLATION OF GLUCOSE - Glucose is phosphorylated to make it more reactive. 2 phosphate groups are added to the glucose from ATP to form HEXOSE BISPHOSPHATE2 - The hesoxe bisphosphate is split into 2 TRIOSE PHOSPHATES3 -The triose phosphates are oxidated by a dehydrogenase enzyme. THe H is taken up by NAD. This forms 2 pyruvate molecules, 2 NADH and 2 net molecules of ATP per molecule of glucose

LINK REACTION AND KREB'S CYCLEPyruvate dehydrogenase and pyruvate decarboxylase remove hydrogen atoms and CO2 from the pyruvate, converting it into ACETATE. The H is accepted by NAD, and the CO2 is excreted. The acetate combines with coA to form ACETYL CoA. Per molecule of glucose, 2 CO2, 2 reduced NAD and 2 acetyl CoA are formed.Acetate is released from acetyl CoA and bonds with oxaloacetate to form citrate. Citrate is dehydrogenated and decarboxylated, producing a 5C compound, CO2 and H. The 5C compound undergoes the same process, forming a 4C compound. The 4C compound has H removed in a series of reactions, where the H is then accepted by FAD and NAD and ATP is produced. Per molecule of pyruvate, 3 NADH, 1 FADH, 1 ATP, 2 CO2 and 1 regenerated oxacoacetate are formed.

OXIDATIVE PHOSPHORYLATIONReduced NAD and FAD release H, which splits into an H+ and e-. The e- is picked up by the first e- carrier and is passed along the carriers until it is accepted by O2 and combined with H+, forming H2O. E- release energy as they pass along the ELECTRON TRANSPORT CHAIN, which is used to pump H+ from the matrix to the intermembrane space, setting up an ELECTROCHEMICAL GRADIENT. H+ diffuse through ATPsynthase proteins in the membrane, which generates energy to form ATP. This process is CHEMISOSMOSIS 

ANAEROBIC RESPIRATIONOxygen is the final electron acceptor in the electron chain, so when it is not present, the electron chain stops, NAD cannot be reused and so the Kreb's cycle and link reaction stop. Anaerobic respiration in mammals involves pyruvate dehydrogenase converting pyruvate into lactate, and the NAD being free to go back and take part in glycolysis. In anaerobic respiration in yeast, ethanal is formed from pyruvate be decarboxyalted, and accepts hyrdogen in a reaction catalysed by ethanol dehydrogenase. The end products are CO2 and ethanol

RESPIRATORY QUOTIENT = Volume of CO2 produced/Volume of O2 consumed

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