Fermentation Section 9.3

Glycolysis Glycolysis can generate energy when oxygen isn’t available BUT, in a few seconds all of a cell’s NADP+ ions are full of electrons No oxygen means no electron transport chain Without NADP+ glycolysis stops Fermentation saves the day…..

Fermentation Cells convert NADH to NAD+ - high energy electrons are passed back to pyruvic acid Glycolysis can continue happening Fermentation is anaerobic – occurs in cell cytoplasm Two types Alcoholic fermentation Lactic acid fermentation

Alcoholic fermentation Yeasts and some other microorganisms use alcoholic fermentation to produce ethyl alcohol and carbon dioxide Used to make bread rise, used to make alcohol

Lactic acid fermentation Most organisms can perfrom lactic acid femernattion No carbon dioxide is given off Lactic acid from bacteria can be used to make cheese, yoghurt, sour cream Acid = sour taste Humans produce lactic acid Muscles are most adapted to do this, as they often need large supplies of ATP

Energy and exercise Humans have three sources of energy for sports ATP already in muscles Enough for a few seconds ATP made by lactic acid formation Enough ATP for 90 seconds (200 – 400 meter sprint…) Large amounts of lactic acid builds up, an oxygen debt that must be repaid

Energy and exercise continued ATP made from cell respiration The only way to supply muscles with energy for a long amount of time Releases energy slowly – why athletes pace themselves Glycogen stored in muscles provides energy for 20 minutes or so After that other molecules are broken down Help people loose weight Allow animals to hibernate At the beginning of a race muscles use all forms of energy, but stored ATP and lactic acid fermentation can only supply energy for a limited time