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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.