Chemical Reactions and

Enzymes

Are processes that change or transform, one set of chemicals into another.

Drive all the activities associated with life.

Involve reactants (starting materials) and products (ending materials). The atoms of the

reactants are rearranged to form the products.

There are two types Endothermic

▪ Absorb energy▪ Breakdownmacromolecules

Exothermic▪ Release energy▪ Build macromolecules

Need some energy to get started The needed energy is called

activation energy.▪ Activation energy is a chemical push

Is required for both exothermic and endothermic reactions.

Is lowered by enzymes▪ Enzymes are biological catalysts that

speed up chemical reactions, but are not used up by them.

Enzymes speed up reactions by lowering the activation energy (Ea) of a reaction. The activation energy is the energy needed to start a reaction.

Different reactions have different activation energies.

reaction (time)

ener

gy

(kJ)

Ea with enzyme

Ea without enzyme

Are large folded proteins that are made of hundreds of amino acids.

All enzymes have active sites Active sites

▪ Form in the protein folds.

▪ Have a complimentary substrate shape.

Speed up chemical reactions by binding with specificmolecules. The specific

molecule is a substrate.

Promote specific chemical reactions

http://www.youtube.com/watch?v=V4OPO6JQLOE

Are affected by heat, acidity, and enzyme concentration Enzymes function with in a certain

temperature range. Enzymes cease to function if the

strength of acids in body fluids is too high or too low.

Enzyme concentration determines if a reaction occurs.

Work with a partner to answer questions 1-3 of Assessment 2.4 on page 53 of your Biology textbook. Write the questions and answers in your notebook. Answer the questions thoughtfully and with complete sentences.