Chemical Reactions and Enzymes

Energy and MatterEnergy and Matter Energy

The ability to do work or cause change

Occurs in various forms Can be converted to another form Forms important to biological

systems are chemical, thermal, electrical and mechanical energy

Free energy is the energy in a system that is available for work

States of MatterStates of Matter Atoms are in constant motion The rate at which atoms or molecules

in a substance move determines its state

Solid Molecules are tightly linked. Little energy

LiquidMolecules are not as

tightly linkedMedium amount of

energy

States of MatterStates of Matter

GasMolecules have little or no attraction to each otherFill the volume of the occupied containerMove most rapidly

To cause a substance to change state, thermal energy (heat) must be added to or removed from a substance

States of MatterStates of Matter

Energy and Chemical Reactions Living things

undergo thousands of chemical reactions as part of the life process

Many are very complex involving multistep sequences called biochemical pathways

Chemical equations represent chemical reactions Reactants are shown on

the left side of the equation

Products are shown on the right side A + B C + D

Energy and Chemical Reactions

Energy TransferEnergy Transfer Much of the energy

organisms need is provided by sugar (food) Undergoes a series

of chemical reactions in which energy is released (cell respiration)

The net release of free energy is called an exothermic reaction

Reactions that involve a net absorption of free energy are called endothermic reactions

Photosynthesis is an example

Energy TransferEnergy Transfer Mix Barium hydroxide and aluminum salt, and the products dissolve in water of hydration. This is VERY COLD!

Most chemical reactions require energy to begin

The amount of energy needed to start the reaction is called activation energy

Energy TransferEnergy Transfer

Certain chemical substances (catalysts) reduce the amount of activation energy required

Biological catalysts are called enzymes

CatalystsCatalysts

Enzymes are an important class of catalysts in living organisms Mostly protein Thousands of different kinds Each specific for a different

chemical reaction

CatalystsCatalysts

Enzyme Structure Enzymes work on

substances called substrates

Substrates must fit into a place on an enzyme called the active site

Enzymes are reusable!

Solutions

SolutionsSolutions A solution is a

mixture in which 2 or more substances are uniformly distributed in another substance

Solute is the substance dissolved in the solution Particles may

be ions, atoms, or molecules

Solvent is the substance in which the solute is dissolved

Water is the universal solvent

SolutionsSolutions

Acids and BasesAcids and Bases One of the most important aspects of a

living system is the degree of acidity or alkalinity

pH ScalepH Scale logarithmic scale

for comparing the relative concentrations of hydronium ions and hydroxide ions in a solution

ranges from 0 to 14

Each pH is 10X stronger than next

e.g. ph 1 is 10 times stronger than ph 2

AcidsAcids Compounds that donate a proton (H+)

when dissolved in a solution. the lower the pH the stronger the acid 0-6 on the pH scale

HCl H+ + Cl-

BasesBases Compounds that accepts a proton (H+)

when dissolved in a solution. the higher the pH the stronger the base 8-14 on the pH scale

NaOH Na+ + OH-

pH 7.0 is neutral

Acids and BasesAcids and Bases

BuffersBuffers

Control of pH is very important

Most enzymes function only within a very narrow pH

Control is accomplished with buffers made by the body

Buffers keep a neutral pH (pH 7)

Buffers neutralize small amounts of either an acid or base added to a solution

Complex buffering systems maintain the pH values of your body’s many fluids at normal and safe levels