CONVERTS ENERGY IN FOOD TO ENERGY IN ATP

 Involves over 25 chemical reactions  Occurs in cytoplasm and mitochondria  Can be divided into three main stages:  1) Glycolysis  2) The Krebs cycle  3) The electron transport chain

 1 st Stage: Glycolysis - cytoplasm—anaerobic ( no O 2 needed )  2 nd Stage: Krebs Cycle - mitochondria—aerobic ( O 2 needed )  3 rd Stage: Electron Transport Chain - mitochondria—aerobic ( O 2 needed )

 Does NOT require oxygen  anaerobic  First step in cellular respiration  Occurs in cytoplasm  Occurs in ALL organisms  One glucose molecule is split to form two molecules of pyruvic acid

 Energy investment phase: 2 ATP needed to start reaction  Energy harvest phase: 4 ATP produced  Net gain: 2 ATP

 Envelope has inner and outer membranes  Inner membrane:  Very highly folded  provides increased surface area  Has many sites where cellular respiration can occur  Encloses thick fluid matrix

 Occurs in matrix of inner mitochondrial membrane  Aerobic – O 2 needed  2 Pyruvic acid  2 Acetyl CoA + 2 CO 2  2 Acetyl CoA  4 CO ATP  Net result: 2 ATP produced

 Occurs on inner mitochondrial membrane  Also called oxidative phosphorylation or chemiosmosis  Aerobic—requires O 2  Electron transport chain works with H + ions and ATP synthase (proteins in membrane) to produce ATP  Generates up to 34 ATP per original glucose molecule

 GLYCOLYSIS = 2 ATP  KREBS CYCLE = 2 ATP  ELECTRON TRANSPORT CHAIN / ATP SYNTHASE = 34 ATP 38 ATP This production results only if O 2 is present

SOME CELLS CAN HARVEST ENERGY WITHOUT OXYGEN

 Process that makes ATP without O 2  ATP produced in fermentation comes entirely from glycolysis  Produces no additional ATP  When O 2 is not present there is an overall net gain of 2 ATP per glucose molecule  Two major types of fermentation:  Lactic acid fermentation  Alcoholic fermentation

 Occurs in muscle cells when O 2 supply is too low  Cellular respiration continues but fermentation is main ATP source  Produces lactic acid - waste product  Results in muscle soreness after strenuous exercise  Relieved after O 2 supply restored

CAUSES MUSCLE PAIN AND CRAMPING

 Yeast: alcoholic fermentation  Produces ethyl alcohol instead of lactic acid under anaerobic conditions  Used in brewing industry  Released CO 2 makes champagne and beer bubbly  Used by bakers to make bread rise

 Fungi & Bacteria: produce lactic acid like muscle cells  Used to flavor yogurt, some cheeses  Other fermentation processes:  Soybeans  soy sauce  Cabbage  sauerkraut