Aim: In what ways are enzymes specific ? Do now: List the ways enzymes are specific So far you know that the shape of an enzymes is specific to the shape of the substrate. When the enzymes fits the combined unit is call the “substrate-enzyme complex” There is another criteria for enzyme action – temperature and pH

Enzymes work best under optimum conditions of temperature Many work best at temperatures close to body temperatures and most lose their ability to catalyze if they are heated above 60 or 70o C. The reason why enzymes are so sensitive to changes in pH and temperature is that such change can affect the interactions that hold the parts of the protein chain in place.

Enzymes work best under optimum conditions of pH Many enzymes work best at a particular pH and stop working if the pH becomes too acidic or alkaline.

Enzyme changes shape and no longer fits the enzyme substrate complex Extreme conditions of temperature and pH cause the enzyme to become denatured Enzyme changes shape and no longer fits the enzyme substrate complex If the shape of the active site is changed, the substrate molecule will no longer be able to form temporary attractions with the protein chain, because the chemical groups needed to do this will no longer be in the right place. We say that the enzyme has become denatured.

Optimum pH Graph pH 7 1.5 Rate 6.0-6.5 7-8 5.5 - 7 7 14 pH Section 38-2 Graph Site Mouth Stomach Small intestine (from pancreas) Duodenum Ileum Large Intestine pH 7 1.5 6.0-6.5 7-8 5.5 - 7 Rate Create graphs showing conditions of pH. 7 14 pH

Cytochrome c is an enzyme that functions in respiration Section 9-1 Mitochondrion Electrons carried in NADH Electrons carried in NADH and FADH2 Pyruvic acid Glucose Electron Transport Chain Krebs Cycle Glycolysis Write the chemical equation for aerobic respiration Glucose + oxygen  carbon dioxide + water Mitochondrion Cytoplasm Go to Section:

Fermentation (without oxygen) Chemical Pathways Section 9-1 Glucose Krebs cycle Electron transport Glycolysis Chemical pathway depends on the evolution of the organism, many bacteria, yeasts are anaerobic Higher organisms are aerobic Alcohol or lactic acid Fermentation (without oxygen) Cytochrome c shuttles H+ to oxygen to produce water during aerobic respiration Go to Section:

Electron transport chain with cytochrome c Where else would cytochrome c function?

Anaerobic respiration This reaction produces 2 ATP’s of energy. Found in yeast and simple organisms. Simple reaction does not go through the Krebs cycle or the electron transport chain. There is also no molecular oxygen to receive the hydrogens to form water.