Pre-AP Biology: Chapter 2—Section 4 Enzymes Ms. Fortenberry

Introduction into Chemical Reactions Chemical Reaction —— a process that changes or transforms one set of chemical into another The elements or compounds that enter into the chemical reaction —— reactants The elements or compounds produced by the chemical reaction —— products Chemical reactions always involve changes in the chemical bonds that join atoms in compounds. Energy changes — some chemical reactions release energy (often spontaneous) and other reactions absorb energy (will not occur without a source of energy)

Activation Energy The energy that is needed to get a reaction started — activation energy

Enzyme Basics: WHAT is an enzyme? Most enzymes are proteins. WHAT does an enzyme do? Acts as a catalyst to accelerate a reaction. Catalyst: a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change.

HOW do enzymes lower activation energy? Enzyme Basics: HOW does an enzyme effect a chemical reaction? Basically, enzymes speed up chemical reactions that take place in cells by lowering the activation energy in starting a reaction. HOW do enzymes lower activation energy? weaken the chemical bonds

Enzymes: are not permanently changed in the process VERY specific to the reaction they catalyze so specific that each enzyme generally catalyzes only one reaction enzymes are reusable by the cell Enzyme names end in “-ase.” sucrase maltase lactase -Due to their specificity, part of an enzyme’s name is usually derived from the reaction it catalyzes.

HOW do enzymes do their job? Enzyme Action: HOW do enzymes do their job? for a chemical reaction to happen, the reactants must collide together with enough energy so that existing bonds break and new bonds form. If there is not enough energy, the reactants will remain unchanged after the reaction.

The Enzyme-Substrate Complex: Enzymes need substrates for a chemical reaction Enzyme with no substrate = no reaction

The Enzyme-Substrate Complex: reactant: a substance that takes part in and undergoes change during a reaction The reactants of enzyme-catalyzed reactions = substrates Enzymes provide a site where reactants can be brought together. This site is known as the active site of the enzyme. The active site reduces the amount of energy needed for the reaction

The Enzyme-Substrate Complex Let’s look at Figure 2-21 on page 52! What is the name of the enzyme? What are the names of the substrates? What is taking place at the enzyme-substrate complex? What are the names of the products? Let’s take a look at Figure 2-22 on page 53! What is taking place in this image? What happens after the substrate binds to the enzyme?

Regulation of Enzyme Activity: Since enzymes are catalysts for reactions — they can be affected by any variable that influences a reaction Enzymes work best at certain pH levels Many enzymes are affected by changes in temperature

Regulation of Enzyme Activity: Most cells contain proteins that help turn key enzymes “on” and “off” at critical stages in the life of the cell In Conclusion: What are some of the essential roles that enzymes play in a cell? regulate chemical pathways make materials that cells need release energy transfer information

Next: Classroom Activity “Enzymes-to-go!” Understanding the lock and key concept Learning specific digestive enzymes

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