NOTES: 9.3 FERMENTATION Vocabulary: -Fermentation -Aerobic -Anaerobic -Glycolysis -Lactic Acid Fermentation -Alcoholic Fermentation

What happens if your cells aren’t getting enough oxygen? ● Krebs Cycle & E.T.C. CANNOT proceed without oxygen ● Instead, FERMENTATION occurs Pyruvic Acid builds up in animal muscle cells & is converted to LACTIC ACID… feel the burn! In other organisms, the pyruvic acid builds up, ferments, and becomes alcohol

● Fermentation: the release of energy from food molecules in the absence of oxygen (anaerobic) ● Enables cells to carry out energy production in the absence of oxygen ● result of glycolysis + fermentation yields 2 ATP molecules per 1 molecule of glucose (not nearly as much energy!!!!)

2 Fermentation Pathways: 1) Alcoholic Fermentation 2) Lactic Acid

2 Fermentation Pathways: 1) Alcoholic Fermentation: ● occurs in yeast cells & some other microorganisms ● pyruvic acid is broken down into a 2-Carbon alcohol plus carbon dioxide

Alcoholic Fermentation: ● Important to brewers & bakers! When yeast in dough runs out of oxygen it ferments, giving off bubbles of carbon dioxide gas—which forms air space in bread Alcohol produced in the dough evaporates when bread is baked *(when the level of alcohol reaches 12%, yeast cells die)

2) Lactic Acid Fermentation: ● pyruvic acid from glycolysis is converted to lactic acid ● lactic acid is produced in muscles during rapid exercise (body can't supply enough O2 to the tissues) ● the build-up of lactic acid causes a burning, painful sensation in your muscles

Energy & Exercise: Quick Energy ● Muscle cells only contain enough ATP for a few seconds of energy, or a “burst” energy e.g. – an emergency, starting gun of race ● When this is gone, cells resort to lactic acid fermentation which can provide enough ATP for about 90 seconds

Energy & Exercise: Long Term Energy ● If a race or energy need is longer, your body must go through cellular respiration to get enough ATP to continue Even well-conditioned athletes have to pace themselves Your body stores energy in muscle cells and liver in the form of GLYCOGEN these stores are enough to last for 15-20 minutes of activity when broken down through cellular respiration After this, your body begins to break down other molecules, including fats, for energy This is why aerobic exercise is beneficial for weight control!!

Long Term Energy: ● some animals rely on stored fat for energy to get them through long periods without food ● EXAMPLE: a bear going into hibernation!