ENERGY An introduction



An introduction


• In physics, defined as “the ability to do work”.

• The vast majority of energy for living things comes from the sun.

• Light energy is only useable by autotrophs – organisms that convert light energy to chemical energy


Autotrophs and Heterotrophs

• Autotroph means “self feed”

• Autotrophs use photosynthesis to make their fuel molecules (glucose)

• They convert light energy to chemical energy.

• Other organisms have to consume other organisms for their food molecules.

• Heterotroph means “other feed”.

• They eat other things for chemical energy

Using Chemical Energy

• Cellular Respiration: the release of useable chemical energy from the breakdown of larger molecules, usually glucose.

• Combustion: a very rapid chemical process (as oxidation) that produces heat and usually light from the breakdown of molecules.

• Cellular respiration is an enzymatically controlled combustion (of sorts).

Measuring Chemical Energy

• Energy has many units

• Calorie

• One calorie is the amount of energy needed to raise one gram of water one degree Celsius or…

• 1 cal = 1 g H


O up 1 ° C

• Measured using a calorimeter