What if there is not enough or no O 2 present? Alcoholic Fermentation (Yeast) Pyruvate + NADH → Ethanol + NAD + CO 2 Used in baking, beer & wine production Lactic Acid Fermentation Pyruvate + NADH → Lactic Acid + NAD Strenuous exercise = can’t get all the O 2 your cells need so use lactic acid fermentation = Sore muscles!!!

Anaerobic Respiration: Fermentation The fate of the 2 pyruvate molecules that are produced by glycolysis depends on the organism involved.

Anaerobic Respiration - Fermentation If no oxygen is available, cells can obtain energy through the process of anaerobic respiration. A common anaerobic process is fermentation. Fermentation is not an efficient process and results in the formation of far fewer ATP molecules than aerobic respiration. There are two primary fermentation processes: 1.Lactic Acid Fermentation 2.Alcohol Fermentation KEY CONCEPT Fermentation allows the production of a small amount of ATP without oxygen.

Anaerobic Respiration - Fermentation Lactic acid fermentation occurs when oxygen is not available. For example, in muscle tissues during rapid and vigorous exercise, muscle cells may be depleted of oxygen. They then switch from respiration to fermentation.

Anaerobic Respiration - Fermentation The pyruvic acid formed during glycolysis is broken down to lactic acid and energy is released (which is used to form ATP). Glucose → Pyruvic acid → Lactic acid + energy

Anaerobic Respiration - Fermentation The process of lactic acid fermentation replaces the process of aerobic respiration so that the cell can have a continual source of energy, even in the absence of oxygen. However this shift is only temporary and cells need oxygen for sustained activity.

Anaerobic Respiration - Fermentation Lactic acid that builds up in the tissue causes a burning, painful sensation.

Anaerobic Respiration - Fermentation Alcohol fermentation occurs in yeasts and some bacteria. Pyruvic acid formed during glycolysis is broken down to produce alcohol and carbon dioxide and is released (which is used to form ATP).

Anaerobic Respiration - Fermentation Glucose → Pyruvic acid → alcohol + carbon dioxide + energy

Anaerobic Respiration - Fermentation Fermentation is used in food production. CheeseVinegarYogurt Soy SauceBreadOlives/Pickles Beer/MeadeWine/Ale [PPT] Anaerobic Respiration - FermentationAnaerobic Respiration - Fermentation

The Beer and Wine Industry In wine making, special strains of yeast are added to grape juice, which is then sealed in airless tanks for weeks. The yeast ferments the sugar in the grapes, glucose. The alcohol content eventually reaches 10-12% and the yeast are killed. Brewers of beer add yeast to barley. The starch in barley is broken down to glucose. In fermenting the glucose, alcohol is produced.

Baking with Yeast Bakers add the yeast Saccharomyces cervisiae to the ingredients for bread. Once inside the dough, the yeast breaks down the starch in the flour to glucose. The yeast then ferments the glucose, producing CO 2 and alcohol. The bubbles of CO 2 cause the bread dough to rise. The alcohol produced evaporates during baking.

Muscle Energy During periods of vigorous exercise, an animal may not be able to provide enough oxygen to the muscles. The muscles will continue to work using ATP from the anerobic breakdown of glucose to pyruvate. Lactic acid accumulates in the muscles and soon fatigue sets in. Lactic acid accumulation can cause cramping of the muscles. After ceasing the strenuous activity, rapid breathing eventually supplies the cells with oxygen. The lactic acid is converted back to pyruvate and aerobic respiration resumes.

Lactic Acid in the Food Industry The flavor of many familiar dairy products is due to lactic acid produced by the fermenting of glucose by the bacterium Lactobacillus. Yogurt, buttermilk, and sour cream, as well as many cheeses, are manufactured by culturing lactic acid- producing bacteria in milk or cream.

**Fermentation & Running** In our bodies certain muscle cells called fast twitch muscles, have less capability for storing & using oxygen than other muscles. When you run & these muscles run short of oxygen, the fast twitch muscles begin using lactic acid fermentation. This allows the muscles to continue to function by producing ATP by glycolysis. The muscles get enough ATP for quick energy spurts, or shall we say sprints, but quickly become fatigued as their stores of glycogen are used up. Eventually you cramp. This is in part because the muscles lack sufficient ATP to continue contracting. Also, lactic acid build up & must be metabolized by the liver. Runners who sprint actually have more muscle cells specialized for lactic acid fermentation than do long distance runners.

**White & Dark Meat** If you want to see what these muscles are like, when you eat chicken or turkey the white meat is fast twitch muscle. The dark meat is what is called slow twitch muscle. This meat is dark because it contains an oxygen building protein called myoglobin. Note that the slow twitch muscles tend to be wing or leg muscles where long term energy endurance is required. The fast twitch muscles tend to be more common in the breast where quick response but not necessarily endurance is needed. Also, wild animals tend to have more slow twitch muscle than their domestic counterparts.