Ch. 9 Cellular Respiration Harvesting Chemical Energy

9.1 Catabolic pathways yield energy by oxidizing organic fuels  Can be aerobic or anaerobic  Cellular respiration vs fermentation  Energy released is used to do work and some is lost as heat  ATP is produced

Oxidation and Reduction  The relocation of electrons releases energy stored in organic molecules  Leo goes ger – lose electron/oxidation, gain electron/reduction(reduction in positive charge)  Oxidizing vs Reducing agent 

Oxidation of organic fuel  Glucose is oxidized and oxygen is reduced  Electrons lose potential energy along the way and energy is released  Enzymes in our cells allow glucose to be oxidized in a series of steps

Stepwise Energy Harvest via NAD+

Electron Transport Chain

The Stages of Cellular Respiration 1. Glycolysis 2. Citric Acid Cycle 3. Oxidative phosphorylation: electron transport and chemiosmosis

Overview of cellular respiration

Substrate-level phosporylation

9.2 Glycolysis

A Closer Look at Glycolysis

9.3 Citric Acid Cycle  Much of the energy remains in the pyruvate molecules  If oxygen is present, pyruvate enters mitochondrion and oxidation is completed by enzymes of the CAC  But first we must convert pyruvate to Acetyl CoA

Conversion of pyruvate to acetyl CoA

A closer look at the citric acid cycle

The Pathway of Electron Transport

Electron Transport Animation  /student_view0/chapter25/animation__el ectron_transport_system_and_atp_synthesis_ _quiz_1_.html /student_view0/chapter25/animation__el ectron_transport_system_and_atp_synthesis_ _quiz_1_.html  dient/movie-flash.htm dient/movie-flash.htm

Fermentation  Glycolysis plus a mechanism to regenerate NAD+ from NADH  1. Alcoholic fermentation – pyruvate is converted to ethyl alcohol plus carbon dioxide  2. Lactic Acid fermentation – pyruvate is converted to lactic acid  Obligate vs facultative anaerobes

Lactic vs alcoholic fermentation

The Evolutionary Significance of Glycolysis  Glycolysis is the most widespread metabolic pathway among Earth’s organisms  The cytosolic location of glycolysis implies great antiquity 

Glycolysis and the citric acid cycle connect to many other metabolic pathways

Biosynthesis

Regulation of Cellular Respiration via feedback mechanisms