Energy of Living Things

Introduction to Photosynthesis and Cellular Respiration Unit

Energy of Living Things

Cells need energy for life

Energy comes from food you eat, directly or indirectly from the sun!

Definitions

a. Metabolism – Sum of all chemical processes occurring in an organism.

b. Autotroph – Organism that obtains energy from sunlight or inorganic substances.

i. Example: PLANTS need sun, water and carbon dioxide (CO2) to make energy Photosynthesis.

1. Photosynthesis – Process by which light energy from the sun is converted into chemical energy.

Definitions cont…

c. Heterotroph – Organisms that must get energy from food sources instead of sunlight and inorganic substances.

1. Example: ANIMAL cells get energy from food Cellular Respiration.

Definitions cont…

I. Cellular Respiration – A metabolic process similar to burning fuel. The process by which living organisms convert energy within food molecules into energy for the cell, ATP.

a. ATP – “adenosine tri-phosphate”, an organic molecule that is the main energy currency of cells.

Thought Question: Energy Flow

Write down what you ate for your last meal.

How can energy in those food molecules be traced back to the sun?

How does cellular energy come from food?

a. Chemical energy is stored in food molecules

b. Energy is released from food molecules with the help of ENZYMES in your body

c. The process takes place in a series, the end product of one reaction is the reactant (starting material) of the next reaction.

d. Each reaction in the series releases ENERGY.

What happens to the energy?

a. Some energy is lost as heat during each reaction.

b. Some energy is stored temporarily as ATP, a portable form of energy in cells.

c. ATP delivers energy to wherever it is needed in a cell.

d. Energy released from ATP can be used to power other chemical reactions, and MOSTLY to drive the activities of the cell.

ATP Molecules & Energy

a. ATP is a nucleotide with two extra energy-storing phosphate groups.

b. Phosphate groups store energy like a compressed spring.

c. Energy is released when the bonds between phosphate groups are broken.

ATP Molecules and Energy

d. Some energy is required to break these bonds, BUT much more energy is released when the bonds are broken.

e. When one phosphate group is removed the molecule is then called, ADP “adenosine di-phosphate” because there are now 2 phosphates (di-) rather than the 3 (tri-) in ATP.

ATP Molecules and Energy

Reactants

ATP

Products

ADP