Enzymes Catalyst – substance that speeds up the rate of a chemical reaction Enzymes – proteins that act as biological catalysts (speed up chemical reactions that take place in cells); do NOT change during the reaction Enzymes help lower the activation energy of a chemical reaction (the energy needed to get a reaction started)

Enzymes The reactants of enzyme-catalyzed reactions are known as substrates Substrates bind to a site on the enzyme called the active site

______________ ___________ Substrate Products Enzyme Active Site

Enzymes The fit between the active site and substrates is so precise that it is often compared to a lock and key Often named by affected substrate; ending in –ase Example: lactose  glucose + galactose Lactase (enzyme) speeds up this reaction of lactose (substrate) Lactase

Enzymes The rate of enzyme activity depends not only on its shape, but it also depends on other factors. temperature pH concentration

Temperature The temperature where the enzyme functions most effectively is called the optimal temperature. If the temperature is raised above OR BELOW the optimal temperature, the rate of enzyme action will decrease.

1.What is the optimal temperature for enzyme A? ________ 2.What is the optimal temperature for enzyme B? ________ 3.Knowing that body temperature is approximately 22 degrees Celsius, which enzyme would work best in your body? __________ A

pH The pH scale is a measure of hydrogen ions in a solution. The pH will also affect the rate of enzyme activity.

Bases Acids NaOH KOH OH HCl H 2 SO 4 H

pH 1.What is the optimal pH for the enzyme found in your stomach ? __________ 2.What is the optimal pH for the enzyme found in your intestine? ___________ Gastric Protease Intestinal Protease

Concentration The rate of enzyme action also depends on the concentration of enzyme present. The larger the concentration of enzyme, the faster the rate of reaction; however, there is still an optimal concentration of enzyme.

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