ENZYMESENZYMES

Energy and Chemical Energy and Chemical ReactionsReactions

Energy for Life ProcessesEnergy for Life Processes Energy – the Energy – the ability to moveability to move or change or change

matter. Light energy, heat energy, matter. Light energy, heat energy, chemical energy, mechanical energy, chemical energy, mechanical energy, and electrical energy.and electrical energy.

Energy can be converted from one form Energy can be converted from one form to another.to another. If you cook an egg in a hot If you cook an egg in a hot pan, heat caused the egg to change pan, heat caused the egg to change color and solidify. The energy color and solidify. The energy transferred to the egg by heat transferred to the egg by heat rearranges the atoms and molecules in rearranges the atoms and molecules in the egg, causing it to go from a liquid to the egg, causing it to go from a liquid to a solid.a solid.

Energy can be Energy can be stored or released by stored or released by chemical reactions.chemical reactions. A chemical A chemical reaction is a process during which reaction is a process during which chemical bondschemical bonds between atoms are between atoms are brokenbroken and new ones are formed, and new ones are formed, producing one or more different producing one or more different substances.substances.

ReactantsReactants: the starting material for : the starting material for chemical reactions.chemical reactions.

Products: the Products: the newly formed newly formed substancessubstances from a chemical reaction from a chemical reaction

Energy in Chemical Energy in Chemical ReactionsReactions

In In chemical reactions, energy is chemical reactions, energy is released and absorbed when chemical released and absorbed when chemical bonds are broken and new ones are bonds are broken and new ones are formed.formed.

Example: energy is released from Example: energy is released from water as water as heatheat, and the water freezes., and the water freezes.

Example: ice absorbs energy as heat Example: ice absorbs energy as heat from the environment, and the ice from the environment, and the ice melts.melts.

Activation EnergyActivation Energy Activation Activation

Energy – the Energy – the energy energy needed to needed to start a start a chemical chemical reactionreaction. . Example: It Example: It takes a few takes a few seconds for a seconds for a car to car to actually start.actually start.

EnzymesEnzymes Enzymes – substances Enzymes – substances

that that increase the speed increase the speed of chemical reactionsof chemical reactions. . Most enzymes are Most enzymes are proteinsproteins that work best that work best at a specified pH. at a specified pH. Another word for Another word for enzymes is enzymes is catalyst.catalyst.

Enzymes help Enzymes help organisms maintain organisms maintain homeostasis. Without homeostasis. Without them, chemical them, chemical reactions would not reactions would not occur quickly enough occur quickly enough to sustain life.to sustain life.

Enzyme SpecificityEnzyme Specificity Substrate Substrate – a substance on which an enzyme – a substance on which an enzyme

acts during a chemical reaction. acts during a chemical reaction. Enzymes Enzymes act only on specific substrates.act only on specific substrates.

Example: the enzyme catalase in our body Example: the enzyme catalase in our body breaks down the poisonous substance breaks down the poisonous substance hydrogen peroxide..hydrogen peroxide..

An enzyme’s shape determines its activity. An enzyme’s shape determines its activity. An enzyme is usually a large protein with An enzyme is usually a large protein with one or more deep folds on its surface. These one or more deep folds on its surface. These folds form pockets called folds form pockets called active sitesactive sites. An . An enzyme’s enzyme’s substrate will fit into the active substrate will fit into the active site.site. Only the specific substrate will fit into Only the specific substrate will fit into the enzyme’s active site.the enzyme’s active site.

How an Enzyme works:How an Enzyme works:Step 1: When an Step 1: When an

enzyme first enzyme first attaches attaches to a substrateto a substrate during during a chemical reaction, a chemical reaction, the enzyme’s shape the enzyme’s shape changes slightly so changes slightly so that the substrate that the substrate fits more tightly in fits more tightly in the enzyme’s active the enzyme’s active site.site.

Step 2: At an active site, an enzyme and a Step 2: At an active site, an enzyme and a substrate interact in a way that reduces substrate interact in a way that reduces the activation energy of the reaction, the activation energy of the reaction, making the substrate more likely to making the substrate more likely to react. react.

Step 3: The reaction is complete when Step 3: The reaction is complete when products have formed. The enzyme is products have formed. The enzyme is now free to catalyze further reactions. now free to catalyze further reactions. Notice, the Notice, the enzyme never changesenzyme never changes, and , and is never harmed.is never harmed.

InhibitorsInhibitors Inhibitors – an inhibitor is Inhibitors – an inhibitor is a substance a substance

that fits into the active site of an that fits into the active site of an enzyme to slow the reactionenzyme to slow the reaction downdown. .