Energy in Compounds

What is energy?The ability to do work In the cell, the energy contained within the

chemical bonds powers the work done.

6 O2 + C6H12O6 ! 6 CO2 + 6 H2O

What is energy?The ability to do work In the cell, the energy contained within the

chemical bonds powers the work done.

6 O2 + C6H12O6 ! 6 CO2 + 6 H2O

Complex molecules (high energy storage)

Low energy storage

What is energy?The ability to do work In the cell, the energy contained within the

chemical bonds powers the work done.

Different chemical bonds contain different amounts of energy (see page 129)

In a chemical reaction, the energy of chemical bonds must be broken in order for a reaction to progress

Calculate the energy required to break the bonds in the following reactants

CH4= 1644 kJ

O2=494 kJ x 2 =988 kJ

TOTAL =2632kJ

Activation Energy (EA)

• all chemical reactions require an initial input of energy, called activation energy (EA)

EA for this reaction is 2632 kJ

In the formation of products, some energy will be released

Energy released as bonds are formed when products are made

EA

Release Energy• Products of reaction will have energy output. • To calculate this, the bond energies of the

products are calculated

Release Energy• When products form, they will have energy

output. • To calculate this, the bond energies of the

products are calculated

CO2= 1598 kJ

H2O= 918 kJ x 2 =1836 kJ

TOTAL= 3434 kJ

Exergonic vs EndergonicIn reactions If products release more

energy then the input of energy-> Exergonic

(energy to break bonds < energy released when new bonds form)

In reactions If products release less

energy then the input of energy-> Endergonic

(energy to break bonds > energy released when new bonds form)

• In living organisms, energy is responsible for all chemical and physical work