Temperature can affect the rate at which chemical reactions happen Low temp = slow reactions High temp faster reactions Enzymes are special ‘helper’ proteins that help a chemical reaction to happen quicker

Macromolecules Atoms come together to form macromolecules important to life Macro = big 1. Proteins (single most important macromolecule for life) 2. Carbohydrates (energy) 3. Lipids (fats, oils, waxes) 4. Nucleic acids (DNA, RNA)

Water is also an important molecule but it is not made by the body It is used in virtually every chemical reaction in our body Water has an unusual structure called a polar molecule that allows for all these different types of reactions to happen A polar molecule has one side that has a slight positive charge & one side that has a slight negative charge

The 7 Characteristics of Life In order for an organism to be considered alive it MUST meet all 7 of the characteristics of life!!! 1. Cells & Organization The cell is the smallest unit that can perform all life’s processes One celled organisms are called unicellular (singlecelled) - Organisms made up of two or more cells are called multicellular

2. Response to their environment A living organism can respond to a stimulus A stimulus is a change in the organisms environment Temperature, too much or not enough water, fertilizer, pollution...

3. Maintain balance (homeostasis) An organism must have a stable inside environment even when the outside environment is constantly changing Ex. You shiver when it is cold to maintain body temperature All living organisms must maintain balance in order to be healthy

4. Metabolism Metabolism is the process of using energy to power functions & growth This energy is in the form of food or nutrients

5. Growth & Development All living things grow & increase in size Development is the process by which an organism becomes a mature adult

6. Reproduction This is the process of producing a new organism that looks like the original During reproduction, hereditary information is passed onto the next generation (DNA, RNA)

Sexual reproduction: when DNA from two different organisms combine to form a new organism The offspring is similar to but not identical to the original organism Asexual reproduction: when there is no comb- ination of DNA from two organisms The offspring is genetically identical to it’s parent

7. Change through time (Evolution) Although individual organisms experience many changes during their lifetime, their basic genetic characteristics do not change. However, populations of organisms change through time (evolve) This is important for the survival of species