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
(photosynthesis)

• 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

• 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).

• 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
2
O up 1 ° C
• Measured using a calorimeter