Introduction to Biology

1. Introduction to Biology Biology 1-2

2. Properties of Life • Made of one or more cells • Uses energy • Grows • Reproduces • Responds to its environment • Maintains a constant internal environment

3. Atoms and Elements • What an organism is made of determines its structure and function. • All matter is made of atoms. • Each different type of atom is called an element.

4. Atoms and Elements cont’d • Each atom is made of three particles: • Proton-a positively charged particle. • Electron-a negatively charged particle. • Neutron-a neutral (no charge) particle. • The number of protons makes each atom different. • An ion is an atom that has gained (negative ion) or lost (positive ion) electrons.

5. Atoms and Elements cont’d • Life requires 25 different elements. • Six essential elements: • Carbon (C) • Hydrogen (H) • Nitrogen (N) • Oxygen (O) • Phosphorus (P) • Sulfur (S)

6. Atoms and Compounds • Atoms are put together to make compounds. • Bonds hold the atoms together. • Different combinations of atoms make different compounds.

7. Acids and Bases • Living organisms are sensitive to acids and bases. • Acid-a compound that gives up hydrogen ions (H+). • Increases the amount of H+. • Base-a compound that picks up hydrogen ions (H+). • Decreases the amount of H+.

8. Chemical Reactions • Life is dependent on chemical reactions • Chemical reactions use atoms from one compound to make other compounds. • Reactant-what is used during the reaction. • Product-what is made during the reaction.

9. Chemical Reactions cont’d • During chemical reactions bonds between atoms are broken. • The atoms are rearranged. • New bonds are formed.