1 / 28

Energy Release in Cells: Photosynthesis, Aerobic & Anaerobic Respiration Mechanisms

This chapter delves into how cells release chemical energy through metabolic reactions, focusing on photosynthesis and cellular respiration. It explains how light energy is converted into glucose (C6H12O6), a process known as photosynthesis, and contrasts it with cellular respiration where stored energy in glucose is converted into usable ATP. Key processes include glycolysis, the Krebs cycle, and the electron transport chain under aerobic conditions, as well as anaerobic respiration techniques like fermentation. This comprehensive overview highlights energy transformation, storage, and usage.

tatum
Télécharger la présentation

Energy Release in Cells: Photosynthesis, Aerobic & Anaerobic Respiration Mechanisms

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 8 How Cells Release Chemical Energy

  2. Metabolic reactions • 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

  3. Cellular respiration • 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

  4. Aerobic respiration • 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

  5. Aerobic respiration • Step 2a—Acetyl-CoA • Pyruvate (3C) combines with CoA • Releases CO2 • NAD+ NADH • Forms acetyle-CoA (2C) • 2 Pyruvate => 2 CO2 + 2 NADH

  6. Aerobic respiration • 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

  7. Aerobic respiration • 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

  8. Aerobic respiration • If no oxygen, electrons can’t pass on • This backs up to NADPH, so no H+ gradients • No ATP forms, starving cells

  9. Aerobic respiration • 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

  10. Anaerobic respiration • 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

  11. Anaerobic respiration • Glycolysis happens normally • 2 Pyruvate, 2 NADH, 2 Net ATP form • Enough energy for many single-celled species • Not enough energy for large organisms

  12. Alcohol fermentation • Glucose  2 Pyruvate  2 Acetaldehyde + 2 CO2 • NADH + Acetaldehyde  Ethanol

  13. Alcohol fermentation • Yeasts • Bread • Beer • Wine

  14. Lactate Fermentation • Glucose  Pyruvate  Lactate

  15. Lactate fermentation • Can spoil food • Some bacteria create food • Cheese, yogurt, buttermilk • Cure meats • Pickle some fruits & vegetables

  16. Lactate fermentation • Muscle cells • Slow-twitch—light, steady, prolonged activity • 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

  17. Energy storage • Glucose absorbed through intestines • When glucose level rises, glucose converted to glycogen • Diverts at glucose-6-phosphate in glycolysis

  18. Energy storage • 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

  19. Using fats • Body stores most fats as triglycerides • When glucose levels fall, triglycerides used • Enzymes remove glycerol

  20. Using fats • Glycerol converted to PGAL • PGAL converted to pyruvate as in glycolysis

  21. Using proteins • 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

More Related