CELLULAR RESPIRATION

Overall Process C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + ENERGY Purpose: Organisms routinely break down complex molecules in controlled steps and use energy released (in the form of ATP) from this catabolic process to do work.

ATP – adenosine triphosphate

Phosphate bonds PO 4 bonds are high energy bonds –Require energy to make –Release energy when broken

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

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 ATP ADP + P

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

1. Glycolysis Breakdown of glucose into pyruvate in cytoplasm w/ or w/o presence of O 2 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  pyruvate change makes 2 ATPs via substrate level phosphorylation and 1 NADH via redox

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

1. Pyruvate is oxidized into Acetyl CoA reducing NAD + into NADH on the way CO 2 is formed 2. Acetyl CoA + oxaloacetic acid → citric acid

3. Citric acid is oxidized forming 2 CO 2 as waste This becomes oxaloacetic acid end of cycle This oxidation powers the reduction of 3 NAD +  3 NADH and 1 FAD +  FADH 2 as well as the phosphorylation of ADP  ATP. Also get e - ’s and protons (H + ) for ETC/Chemiosomosis

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

Final electron acceptor is O 2 2H + (from FADH 2 and NADH) 2e - (from FADH 2 and NADH) ½ O 2 H 2 O!

Key Points No ATP is generated during ETC; ATP comes from chemiosmosis! Source of e - = NADH and FADH 2 reduction Source of H + = same as above!

Phosphorylation… 1.Photophosphorylation – plants use energy from sun to drive phosphorylation of ADP  ATP 2.Substrate-level phosphorylation – glycolysis and Krebs cycle use proteins (substrates) to phosphorylate ADP  ATP 3.Oxidative phosphorylation – in ETC, redox reactions drive production of ATP This is where most of ATP generated from cell respiration comes from!

Fermentation Process whereby cells produce ATP without O 2 Alcohol fermentation – pyruvate is converted to ethanol CO 2 released Lactic acid fermentation – pyruvate is reduced directly by NADH to form lactate No CO 2 released