CELLULAR RESPIRATION

1. CELLULARRESPIRATION

2. Overall Process C6H12O6 + 6O2 6CO2 + 6H2O + ENERGY Purpose: Organisms routinely break down complex molecules in controlled stepsand use energy released (in the form of ATP) from this catabolic process to do work.

3. ATP – adenosine triphosphate

4. Phosphate bonds • PO4 bonds are high energy bonds • Require energy to make • Release energy when broken

5. Phosphorylation • Adding a phosphate group to any molecule • Ex: ADP + Pi ATP • Oxidative phosphorylation – phosphorylation results from redox reactions • Substrate-level phosphorylation – phosphate group transfers from a molecule (“substrate”) instead of ADP + Pi ADP

7. How ATP Drives Cellular Work • Transport Work: • ATP Phosphorylates Transport Proteins • Mechanical Work: • ATP Phosphorylates Motor Proteins • Chemical Work: • ATP Phosphorylates Key Reactants • Phosphate groups are removed and recycled as work is performed ADP + P ATP

8. Cellular Respiration • Divided into 3 parts: • 1. Glycolysis • 2. Krebs Cycle (aka Citric Acid Cycle) or Fermentation • 3. Oxidative phosphorylation (ETC & Chemiosmosis)

10. 1. Glycolysis • Breakdown of glucose into pyruvate in cytoplasm w/ or w/o presence of O2 • 2 phases: • Investment phase: use 2 ATP to break up glucose into 2 PGAL (C-C-C-p) • Payoff phase: each PGAL turns into pyruvate (C-C-C) • Each PGAL  pyruvatechange makes 2 ATPs via substrate level phosphorylation and 1 NADH via redox

13. Occurs in presence of O2 Occurs in inner space or matrix of mitochondria Complete oxidation of glucose to CO2 occurs here 2. Krebs Cycle (aka citric acid cycle)

14. 1. Pyruvate is oxidized into Acetyl CoA reducing NAD+ into NADH on the way • CO2 is formed • 2. Acetyl CoA + oxaloaceticacid → citric acid

15. 3. Citric acid is oxidized forming 2 CO2 as waste • This becomes oxaloaceticacid again@ end of cycle • This oxidation powers the reduction of 3 NAD+ 3 NADHand 1 FAD+ FADH2as well as the phosphorylation of ADP  ATP. • Also get e-’s and protons (H+) for ETC/Chemiosomosis

18. ETC • Occurs in the inner membrane of mitochondrial matrix • Energy released as e- travels down • ETC is used to establish a proton • gradient

19. Final electron acceptor is O2 • 2H+ (from FADH2 and NADH) • 2e- (from FADH2 and NADH) • ½ O2 • H2O!

21. Key Points • No ATP is generated during ETC; ATP comes from chemiosmosis! • Source of e- = NADH and FADH2 reduction • Source of H+ = same as above!

22. Phosphorylation… • Photophosphorylation– plants use energy from sun to drive phosphorylation of ADP  ATP • Substrate-level phosphorylation – glycolysis and Krebs cycle use proteins (substrates) to phosphorylate ADP  ATP • Oxidative phosphorylation – in ETC, redox reactions drive production of ATP • This is where most of ATP generated from cell respiration comes from!

24. Fermentation • Process whereby cells produce ATP without O2 • Alcohol fermentation – pyruvate is converted to ethanol • CO2 released • Lactic acid fermentation – pyruvate is reduced directly by NADH to form lactate • No CO2 released