How Cells Release Chemical Energy ï‚‍ Photosynthesis ï‚ Light energy converted into stored energy (glucose) ï‚ CO 2 + H 2 O => C 6 H 12 O 6 (glucose) + O

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  • How Cells Release Chemical Energy
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  • Photosynthesis Light energy converted into stored energy (glucose) CO 2 + H 2 O => C 6 H 12 O 6 (glucose) + O 2 Endergonic Cellular Respiration Stored energy (glucose) converted into useable energy (ATP) C 6 H 12 O 6 (glucose) + O 2 => CO 2 + H 2 O Exergonic
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  • Aerobic Respiration Requires oxygen High energy (ATP) yield Glycolysiscytoplasm Krebs Cyclemitochondrial matrix Electron Transport Systemcristae Anaerobic Respiration Doesnt require oxygen Organisms without mitochondria Low energy yield
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  • Step 1Glycolysis 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
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  • Step 2aAcetyl-CoA Pyruvate (3C) combines with CoA Releases CO 2 NAD + NADH Forms acetyle-CoA (2C) 2 Pyruvate => 2 CO 2 + 2 NADH
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  • Step 2bKrebs Cycle 2 Acetyl-CoA enter Transfers carbons to oxaloacetate (C4), forming citrate (C6) Cycles through steps to rearrange citrate 2 CO 2 released Ends forming oxaloacetate Cycle starts again Net gain of 4 CO 2, 6 NADH, 2 FADH 2, 2 ATP
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  • Step 3Electron Transfer Phosphorylation NADH & FADH 2 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 O 2, combines with H + to form H 2 O
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  • If no oxygen, electrons cant pass on This backs up to NADPH, so no H + gradients No ATP forms, starving cells
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  • Glycolysis Glucose + 2ATP 4ATP + 2NADH + 2 Pyruvate Intermediate 2 Pyruvate 2CO 2 + 2NADH + 2 Acetyl-CoA Krebs Cycle 2 Acetyl-CoA 6NADH + 2ATP + 2FADH 2 Electron Transfer 10NADH + 2FADH 2 32ATP + 4CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 6H 2 O + 6CO 2 + 36 ATP + heat
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  • Fermenters Protists, bacteria Marshes, bogs, deep sea, animal gut, sewage, canned food Some die when exposed to O 2 Some indifferent to O 2 Some can use O 2, but switch to fermentation when none around
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  • Glycolysis happens normally 2 Pyruvate, 2 NADH, 2 Net ATP form Enough energy for many single-celled species Not enough energy for large organisms
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  • Glucose 2 Pyruvate 2 Acetaldehyde + 2 CO 2 NADH + Acetaldehyde Ethanol
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  • Yeasts Bread Beer Wine
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  • Glucose Pyruvate Lactate
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  • Can spoil food Some bacteria create food Cheese, yogurt, buttermilk Cure meats Pickle some fruits & vegetables
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  • Muscle cells Slow-twitchlight, steady, prolonged activity Marathons, bird migrations Many mitochondria Only aerobic respiration dark meat in birds Fast-twitchimmediate, intense energy Weight lifting, sprinting Few mitochondria Lactate fermentation Produce ATP quickly, but not for long white meat in birds
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  • Glucose absorbed through intestines When glucose level rises, glucose converted to glycogen Diverts at glucose-6- phosphate in glycolysis
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  • 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
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  • Body stores most fats as triglycerides When glucose levels fall, triglycerides used Enzymes remove glycerol
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  • Glycerol converted to PGAL PGAL converted to pyruvate as in glycolysis
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  • Happens when eat too many proteins, or when carbohydrates & fats used Enzymes break down protein molecules Ammonia (NH 3 ) removed Leftover carbon backbone split Forms acetyl-CoA, pyruvate, or intermediate of Krebs cycle Specific amino acid determines which is formed

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