Chapter 8 Notes

Energy and Life


What is Energy? 




What is work?



Where do we get our energy?





Autotrophs: Organisms that can make their own food using light energy from the sun.


Ex. Land plants, algae, some protests and some bacteria


Heterotrophs: Organisms that cannot directly use the sun’s energy, but obtain their energy from the foods they consume.


 Ex.  Animals, some protists, some bacteria, fungus


Energy comes in many forms including light, heat, and electricity.  This energy can be stored in chemical compounds.


All living things run on the chemical energy in the bond of ATP (adenosine triphosphate): The principal chemical compound that cells use to store and release energy.


ATP consists of 3 parts:

1. adenine

2. ribose (a 5-carbon sugar)

3. three phosphate groups

The three phosphate groups store and release the energy needed by the cells.



Releasing Energy:


ATP is like a charged battery ready to be used. 


·    To release the energy, the chemical bond between the second and third phosphates is broken.  The cell can easily break this bond whenever energy is needed.


  •When a cell has excess energy it can store it by adding a phosphate group to ADP molecules, producing ATP.


Biochemical Uses:


ATP is used in several processes in the body including:




ATP is a good source of transferring energy, but it cannot store large amounts of energy like glucose can.

      Cells keep a small amount of ATP and keep recharging it.