SBI 4U Cellular Respiration Controlling Aerobic Respiration SBI 4U Cellular Respiration Metabolism of Nutrients Other Than Glucose Proteins Amino acids Carbohydrates Starch Glucose Lipids Glycogen Glycerol Glucose-6phosphate PGAL Pyruvate Acetyl-CoA Kreb’s Cycle NH3 CO2 H2O Fatty Acids SBI 4U Cellular Respiration Anaerobic Pathways: Glycolysis (the same as for aerobic respiration) Fermentation: two types depending on the organism 1. Alcoholic (Ethanol) Fermentation glucose 2 pyruvic acid 2acetaldehyde 2 ethanol Occurs in yeasts and bacteria that live in absence of oxygen This form of fermentation allows us to produce wine from grapes and beer from grains, make bread and pastries, and soy sauce. A large quantity of energy remains “locked” in the alcohol molecule; it can therefore be used as fuel. Today, ethanol fuel is giving us new fuels for our internal combustion engines, replacing the need for gasoline from fossil fuels. 2. Lactic Acid Fermentation Occurs when there is an oxygen deficit glucose 2 pyruvic acid 2 lactic acid SBI 4U Cellular Respiration As activity levels increase, muscles rapidly deplete the energy in the available ATP; therefore, the cellular respiration rate increases (because the need for O2 increases). The heart/lungs may not always be able to provide enough O2; if there is a lack of O2, the mitochondria shut down, but glycolysis proceeds (if there is enough glucose). However, as pyruvic acid molecules accumulate in the cytoplasm, glycolysis slows down. Creatine phosphate (CP) provides the necessary energy to produce ATP (short duration). Energy is stored in the muscle as CP. CP breakdown is the fastest anaerobic method of ATP production CP + ADP C + ATP The body still needs to stop and rest. As lactic acid builds up, there is increased muscle fatigue (“burn”), and as the acidity level in the cells increases (pH ↓), muscles cannot contract. When O2 is again present, lactic acid diffuses into the blood where it is carried to the liver to be converted back into glucose through the process of gluconeogenesis. (Gluconeogenesis cannot take place in the muscles because they lack the necessary enzyme for the reaction to proceed When activity levels decrease, enough O2 becomes available so cellular respiration may take place, CP levels are replenished and lactic acid (waste) is eliminated.