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Chemical Reactions and Enzymes
Section 2.4
Chemical Reaction Review• Reactions involve changes in the chemical
bonds of substances.• Mass and energy are conserved.• Reaction rates vary. (rusting vs. combustion)• Reactants and products
Energy in Reactions
• Some chemical reactions release energy (exothermic) in the form of heat, light, and sound. – Exothermic reactions can to be spontaneous.
• Example: cell respiration
• Some reactions absorb energy (endothermic).– Endothermic reactions will not occur without a source
of energy.• Example: photosynthesis
Exothermic reactionEndothermic reaction
Enzymes• Enzymes are proteins that act as biological catalysts which
speed up chemical reactions that take place in cells.• Without enzymes, some biological processes would happen
too slowly to maintain homeostasis.• Enzymes are very specific, generally catalyzing only one
chemical reaction, from which the name of the enzyme is derived.
Enzyme Substrates• Substrates are the reactants of enzyme
catalyzed reactions.• Substrates bind to a site on the enzyme called
the active site.• The fit is so precise that the active site is
compared to a lock and key.• http://www.youtube.com/watch?v=0XGiIE9b9QU
Enzyme Regulation• Temperature, pH, and regulatory molecules can
affect the activity of enzymes.• The enzyme can become denatured.• http://www.youtube.com/watch?v=E-_r3omrnxw• What is an inhibitor? How can inhibitors change
enzyme activity?