Chapter 8.1 Energy and Life

Energy is the ability to do work. Living things need energy at all times!

Autotrophs and Heterotrophs Energy comes from food. Autotrophs – plants and other types of organisms that are able to use light energy from the sun to produce food. Heterotrophs – other animals that cannot directly use the sun’s energy – they must eat other organisms.

Chemical Energy and ATP Energy can be store in chemical compounds – these are bonds between atoms. ATP (adenosine triphosphate) is the main source of energy in organisms. It is made of adenine, a 5-carbon sugar called ribose, and 3 phosphate groups. The 3 phosphates are where energy is stored and able to be released.

Storing Energy ADP (adenosine diphosphate) is like ATP except it only has 2 phosphate groups. The difference between the 2 is key to how the energy is stored. When adding that third phosphate it takes a lot of energy to add that phosphate on, so once there is a bond between the 2 phosphates there is a lot of energy stored there.

Releasing Energy Energy is released by breaking the chemical bond between the phosphates. ATP is the basic energy source of all cells. Think of it like a rechargeable battery – it is fully charged when it has 3 phosphates, it gives off energy when it loses a phosphate, a phosphate can then be added back on to restore stored energy.

Using Biochemical Energy One use of biochemical energy is in active transport. Many cells have a sodium-potassium pump. This pumps sodium ions out of the cell and potassium ions into the cell. ATP is necessary for that to happen – it is the energy that makes the motor for the pump run. ATP doesn’t store large amounts of energy, it gives small amount of energy.