Energy and Life 8-1

Autotrophs & Heterotrophs Energy is the ability to do work Nearly every activity, and every organism depends on energy Energy that living things require comes from food

Plants are able to use light energy from the sun to make their own food Plants and other organisms that make their own food are called autotrophs

Organisms that cannot use the sun’s energy to produce their own food are called heterotrophs Heterotrophs get energy from things they eat or decompose

Chemical Energy and ATP Energy comes in many forms including Light Heat Electricity Chemical bonds

Living organisms use chemical compounds Principal compound cells use to store and release energy is Adenosine triphosphate or ATP ATP consists of adenine 5-carbon sugar ribose 3 phosphate groups Keys to ATP’s ability to store and release energy

Storing Energy Adenosine diphosphate, or ADP, looks like ATP but only has 2 phosphate Having only 2 P-groups is the key to organisms abililty to store energy

When cells have energy available, they can store small amounts of energy by adding a phosphate group to ADP Energy is stored in the bonds between each of the P-groups

Releasing Energy Energy is released from ATP breaking the bonds between the 2nd and 3rd P- groups So, by adding or subtracting a phosphate group, cells can store and release energy as needed

Using Biochemical Energy Cells use energy for active transport protein synthesis muscle contractions ATP energy is used to power sodium- potassium pumps located in the cell membrane

This is a form of active transport because Na+ ions are pumped out of the cell and K- are pumped into the cell Molecules move against a concentration gradient While ATP is a useful source of energy, cells only have enough ATP to last for a few seconds

ATP molecules are not good at long term storage of large amounts of energy A single molecule of glucose stores more than 90x the chemical energy of one ATP Cells only store small amounts of ATP because it can easily be regenerated from ADP by using the energy stored in food