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.