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Chapter 2.4
Energy and Chemical Reactions
ObjectivesEvaluate the importance of energy to
living things.
Relate energy and chemical reations.
Describe the role of enzymes in chemical reactions.
Identify the effect of enzymes on food molecules.
Chemical Reactions in Living Things
Chemical reactions occur in laboratories…
but is that the only place?
Chemical reactions occur in every living cell!
Chemical Reactions
Reactants Products
A + B AB
Glucose + O2 CO2 + H2O
MetabolismAll of the chemical reactions
occurring in an organism
Chemical reactions can release energy
Your cells breakdown glucose
The energy released is used to make proteins and others needed molecules
Chemical reactions that build molecules need energy
Reactants
Products
Chemical reactions need some energy to get started.
Activation energyThe energy needed to start a
reaction
Climbing a slide is like adding the necessary activation energy for a reaction to proceed
Enzymes hasten chemical reactions by lowering activation
energy.
Enzyme
A protein that can hasten a chemical reaction by lowering activation energy
CatalystMakes a chemical reaction
proceed faster but is not used up by the reaction
How Enzymes Work
Cells have 100’s of different enzymes!
Each enzyme promotes a different chemical reaction
Different cells have different enzymes
Nerve cells have different chemical reactions occurring than red blood cells and so they have different enzymes.
The active enzymes in a cell direct reaction traffic just as a traffic light
directs traffic
Enzymes are very sensitive
Extremes of temperature can cause them to shut down or be destroyed (denatured)
OR…….
May cause them to begin working.
Darker pigment is produced in cooler areas of Siamese cats
pH Can Also Affect Enzymes
Too much acid or not enough acid causes enzymes to “turn off”.
It can even destroy them by changing their shape.
Except for pepsin. an enzyme that functions in the stomach's acid environment
Enzyme rates can also be affected easily.
The greater the enzyme concentration, the faster the reaction will proceed.
Increasing enzyme concentration, speeds up a reaction.
A very small amount of enzyme speeds up reactions somewhat.
A large amount of enzyme speeds up the work, easily.
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