Cellular Respiration -Process that releases energy by breaking down glucose and other food molecules in the presence of oxygen Equation: 6O2 + C6H12O6  6CO2 + 6H2O + energy oxygen + glucose  carbon dioxide + water + energy *takes place in three steps *glycolysis Krebs cycle  e- transport chain

to the electron transport chain First Step of Respiration: Glycolysis- process in which one molecule of glucose is broken in half, producing 2 molecules of pyruvic acid (a 3-carbon compound) GLUCOSE 2 PYRUVIC ACID to the electron transport chain

-Even though glycolysis releases energy, it still needs energy to get going. ATP production *2 ATP used up in beginning *after completion of glycolysis, 4 ATP made *net gain of 2 ATP NADH production *electron carrier is NAD+ *accepts a pair of electrons and becomes NADH

-glycolysis does not require oxygen -glycolysis takes place in the cytoplasm -Krebs cycle and electron transport chain take place in the mitochondria

-If no oxygen then glycolysis is followed by fermentation -If no oxygen then glycolysis is followed by fermentation. fermentation- releases energy from food molecules by producing ATP in the absence of oxygen *fermentation is an anaerobic process anaerobic- does not require oxygen (not in air) -there are two types of fermentation: alcoholic and lactic acid

alcoholic fermentation- produces carbon dioxide as well as alcohol and NAD+ from pyruvic acid *used to make beers/wines and makes breads rise lactic acid fermentation- produces lactic acid and NAD+ from pyruvic acid *lactic acid is produced in your muscles when you exercise to make up for oxygen depletion *causes muscle soreness

At the end of glycolysis, about 90% of energy is still unused -it is locked in high energy electrons of pyruvic acid -to get the rest of the energy, the cell needs oxygen for the last two steps of respiration aerobic- process that requires oxygen

The Krebs Cycle *takes place in the mitochondria -pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reactions *also known as citric acid cycle b/c citric acid is the first compound formed -electron carriers are produced during the Krebs cycle

-The high energy electron carriers then drop the electrons off- electron transport chain -the chain is a series of proteins that pass the electrons, with every pass, H+ ions build creating a charge, results in ATP production -at end of chain, electrons are passed to oxygen and create water *occurs in all types of organisms

The Totals Glycolysis used 2 ATP, made 4 ATP The Totals Glycolysis used 2 ATP, made 4 ATP *net gain of 2 ATP Krebs cycle/Electron Transport Chain *make 34 ATP TOTAL = 36 ATP (38% of energy from glucose) *rest lost as heat

Comparing Photosynthesis and Cellular Respiration Function Energy capture Energy release Location chloroplasts Mitochondria Reactants CO2 and H20 C6H12O6 and O2 Products Equation 6CO2 + 6H20  C6H12O6 + 6O2 *need energy C6H12O6 + 6O2  6CO2 + 6H20 *energy released