Transcript PowerPoint
How Cells Release Chemical Energy Photosynthesis Light energy converted into stored energy (glucose) CO2 + H2O => C6H12O6 (glucose) + O2 Endergonic Cellular Respiration Stored energy (glucose) converted into useable energy (ATP) C6H12O6 (glucose) + O2 => CO2 + H2O Exergonic Aerobic Respiration Requires oxygen High energy (ATP) yield Glycolysis—cytoplasm Kreb’s Cycle—mitochondrial matrix Electron Transport System—cristae Anaerobic Respiration Doesn’t require oxygen Organisms without mitochondria Low energy yield Step 1—Glycolysis Glucose (6C) broken down into two PGAL (3C) PGAL restructured into pyruvate Produces 2 NADH Requires 2 ATP to start Produces 4 ATP Net gain of 2 ATP Glucose P-Glucose 2 Pyruvate Step 2a—Acetyl-CoA Pyruvate (3C) combines with CoA Releases CO2 NAD+ NADH Forms acetyle-CoA (2C) 2 Pyruvate => 2 CO2 + 2 NADH Step 2b—Krebs Cycle 2 Acetyl-CoA enter Transfers carbons to oxaloacetate (C4), forming citrate (C6) Cycles through steps to rearrange citrate 2 CO2 released Ends forming oxaloacetate Cycle starts again Net gain of 4 CO2, 6 NADH, 2 FADH2, 2 ATP Step 3—Electron Transfer Phosphorylation NADH & FADH2 from previous steps start chain Electrons flow through “chain” of membrane proteins Each protein then takes H+ from above molecules and pumps them into intermembrane space This sets up concentration gradient H+ moves down gradient through ATP synthase Movement forms ATP from ADP & P (32 net gain) Ends with electrons passed to O2, combines with H+ to form H2O If no oxygen, electrons can’t pass on This backs up to NADPH, so no H+ gradients No ATP forms, starving cells Glycolysis Glucose + 2ATP 4ATP + 2NADH + 2 Pyruvate Intermediate 2 Pyruvate 2CO2 + 2NADH + 2 Acetyl-CoA Krebs Cycle 2 Acetyl-CoA 6NADH + 2ATP + 2FADH2 Electron Transfer 10NADH + 2FADH2 32ATP + 4CO2 + 6H2O C6H12O6 + 6O2 6H2O + 6CO2 + 36 ATP + heat Fermenters Protists, bacteria Marshes, bogs, deep sea, animal gut, sewage, canned food Some die when exposed to O2 Some indifferent to O2 Some can use O2, but switch to fermentation when none around Glycolysis happens normally 2 Pyruvate, 2 NADH, 2 Net ATP form Enough energy for many single-celled species Not enough energy for large organisms Glucose 2 Pyruvate 2 Acetaldehyde + 2 CO2 NADH + Acetaldehyde Ethanol Yeasts Bread Beer Wine Glucose Pyruvate Lactate Can spoil food Some bacteria create food Cheese, yogurt, buttermilk Cure meats Pickle some fruits & vegetables Muscle Slow-twitch—light, steady, prolonged activity cells Marathons, bird migrations Many mitochondria Only aerobic respiration “dark” meat in birds Fast-twitch—immediate, intense energy Weight lifting, sprinting Few mitochondria Lactate fermentation Produce ATP quickly, but not for long “white” meat in birds Glucose absorbed through intestines When glucose level rises, glucose converted to glycogen Diverts at glucose-6phosphate in glycolysis Glycogen is storage polysaccharide Stores in liver & muscles With low blood glucose, insulin released This triggers glycogen to convert back to glucose If too many carbohydrates/glucose in blood, acetyl-CoA diverted & made into fatty acid Body stores most fats as triglycerides When glucose levels fall, triglycerides used Enzymes remove glycerol Glycerol converted to PGAL PGAL converted to pyruvate as in glycolysis Happens when eat too many proteins, or when carbohydrates & fats used Enzymes break down protein molecules Ammonia (NH3) removed Leftover carbon backbone split Forms acetyl-CoA, pyruvate, or intermediate of Krebs cycle Specific amino acid determines which is formed