Cellular Respiration Process where living organisms convert the energy in glucose into usable cellular energy (ATP) Too much energy in glucose to be released at once, needs to be converted into smaller ATP molecules High energy C-C & C-H bonds converted into C-O & O-H bonds Each glucose can be broken down to form 36 or 38 ATP Only 36% of energy in glucose is converted to ATP; rest is lost as heat (a car uses ~25% of energy from fuel)

Cellular Respiration Glycolysis is the first stage of respiration and occurs in the cytoplasm of the cell Glycolysis (Glyco= sweet; lysis= to cut) Splits Glucose (6 carbons) into 2 Pyruvic Acid (3 carbons) Does NOT need O2 to occur Uses 2 ATP to start; makes 4 ATP and NADH Controlled by an allosteric enzyme – 2 active sites; allosteric effector (ATP) must attach first to change the shape of the 2nd active site

Cellular Respiration 2 Types of Cellular Respiration: 1. Anaerobic Respiration (aka: Fermentation) Occurs without O2 Occurs in the cytoplasm Uses pyruvic acid from glycolysis Enzymes required Makes 2 ATP per glucose A) Alcohol Fermentation – creates ATP, alcohol, & CO2 Ex: Yeast B) Lactic Acid Fermentation – creates ATP, CO2, & lactic acid Ex: Muscle cells

Cellular Respiration 2. Aerobic Respiration Krebs Cycle Occurs with O2 in the mitochondria 95% of a cells energy is through aerobic pathway Also uses pyruvic acid from glycolysis Creates 34 ATP per glucose Enzymes required for the Krebs Cycle Chemical reaction: O2 + C6H12O6 ATP + CO2 + H2O 2 Stages: Krebs Cycle Electron Transport Chain (E.T.C.)

Cellular Respiration Krebs Cycle (aka: Citric Acid Cycle): Pyruvic acid reacts with coenzyme A to form acetyl coenzyme A (acetyl CoA) Krebs Cycle (aka: Citric Acid Cycle): Occurs in the mitochondrial matrix Acetyl CoA goes into the Krebs Cycle Acetyl CoA combines with Oxaloacetic acid to create Citric Acid Citric acid is made into a 5-carbon compound; produces CO2 and NADH As a 4-carbon compound is produced, another CO2 and 2 ATP are made FADH2 is produced 4-Carbon molecule is made back into oxaloacetic acid to restart cycle

Cellular Respiration Electron Transport Chain: Occurs in the inner membrane of the mitochondria NADH & FADH2 made in previous steps give up electrons and H+ Electrons are passed down the chain, pumping H+ across the membrane H+ move back to the other side through ATP Synthase and ATP is produced (32 ATP) O2 accepts H+ and forms H2O