ATP & Energy Transfer Yay!

Energy Release Glucose is the main source of energy in a cell Respiration releases the energy stored in the glucose This is controlled by enzymes - involves lots of reactions Some of the energy is converted into heat - the rest of the energy is used for…..

ATP ATP is an immediate source of energy (in muscles etc.) Made of Adenosine – adenine + ribose and 3 inorganic phosphates ATP is converted into ADP + Pi to release energy ATP can be reformed from ADP Glucose provides energy for ATP regeneration

Role of ATP Makes energy for many processes: E.g. muscle contraction, protein synthesis, transmission of nerve impulses Links processes that consume energy, and release energy 2 million ATP molecules/sec used (RAPID TURNOVER) Only 50g in the whole body Constantly regenerated (400g/hr)

Oxidation / Reduction Oxidation - the release of an electron from a substance Substance becomes oxidised Reduction – gain of an electron Substance becomes reduced Reactions often coupled together

Chemistry of Respiration The release of chemical energy from food by oxidation Stage 1 -GLYCOLYSIS (in cytoplasm) Net gain of 2 ATP Hydrogen (H) is released and joined to NAD (a co-enzyme) Oxygen not needed for this stage Occurs in the cytoplasm (Pyruvic Acid)

Mitochondria Organelles in the cytoplasm Site of aerobic respiration Cristae – membrane folds - site of ATP production (large surface area) More cristae = more ATP production Central matrix – Fluid-filled (contains enzymes) Many reactions occur in the matrix

Fate of pyruvic acid – aerobic respiration Converted into acetyl CoA in the central matrix Conversion produces 2CO2 & 2NADH2 Acetyl CoA then enters the Kreb’s/Citric Acid cycle Net release of 6CO2 & 10NADH2 Decarboxylase enzymes control CO2 formation CO2 released as waste Dehydrogenase enzymes control NADH2 formation Pyruvic Acid Anaerobic Respiration Aerobic Respiration

Kreb’s Cycle

Hydrogen transfer system 12NADH2 are produced from glycolysis/Kreb’s cycle Passed to a series of carriers - the CYTOCHROME system Carriers on stalked particles on the cristae These use H+ ions from NADH2 - ions form ATP from ADP +Pi This is oxidative phosphorylation Each NADH2 forms 3ATP Glucose produces a gain of 38ATP - 2 from glycolysis, 36 from aerobic respiration CRISTAE STALKED PARTICLES

Role of oxygen Accepts the final hydrogen to make water Controlled by cytochrome oxidase Without oxygen process cannot go beyond glycolysis

Anaerobic Respiration Glucose only partially broken down Oxygen absent Only glycolysis occurs Net gain of 2ATP only Alternative pathway occurs If oxygen returns, lactic acid converted back into pyruvic acid - oxygen debt repaid Pyruvic acid then enters aerobic pathway Oxygen