1. CHEMISTRY Atom = smallest particle of an element = smallest building block of organisms Chemical symbols = set of abbreviations which represent the atoms

2. Biologically Important Elements NameSymbol OxygenO CarbonC HydrogenH NitrogenN PhosphorusP CalciumCa

3. What four atoms make about 96% of human body weight?

4. Molecule = two or more atoms chemically bonded together Molecular formula = shorthand method for describing the chemical composition of a molecule or compound. Any charge on the molecule is written as a superscript following the symbol. If the molecule consists of more than one atom of a given element the number of atoms is written as a subscript following the symbol.

5. + indicates positive charge ↘ H 2 O Na +  indicates two atoms of hydrogen

6. Biologically Important Molecules NameFormula WaterH 2 O Carbon dioxideCO 2 OxygenO 2 NitrogenN 2 GlucoseC 6 H 12 O 6 AmmoniaNH 3

7. Different ways to represent a molecule

8. Air Molecules

9. NameFormula HydrogenH + CalciumCa +2 PhosphatePO 4 -3 SodiumNa + ChlorideCl - NitrateNO 3 - AmmoniumNH 4 + Ion = atom or molecule with a charge Biologically Important Ions

10. Chemical reaction = change of one or more substances into one or more different substances Reactants = substances that participate in (enter into) a chemical reaction = what you start with Products = substances formed by a chemical reaction = what you end up with

11. Chemical equation = description of a chemical reaction, with reactants written on the left, products written on the right and an arrow in the center. The arrow indicates that a change has occurred. The number of molecules is written ahead of the molecular formula.

12. ENZYMES Enzymes are proteins which act as catalysts that speed up specific chemical reactions in living organisms. Enzymes are how living cells control chemical reactions.

13. Some of the same chemical reactions also occur in the nonliving world. If you could ignite a cube of sugar with a match in the presence of oxygen, you would see a flame and feel the heat as the sugar burns to ash. The light and heat are energy released from the bonds that held the atoms of the sugar molecules together.

14. Without Enzymes the reaction is hard to control and only produces heat & light

15. With enzymes the reaction can be controlled and the energy transferred to an ATP molecule, which cells can use to do work

16. Four Groups of Biological Molecules Why does this list of molecules look like the nutrition label on foods?

17. Biological molecules have a backbone or skeleton made up of carbon atoms So, we are called carbon-based life forms on Earth

18. Glucose molecules (C 6 H 12 O 6 ) are an important energy source for many living cells

19. Glucose molecules can be stored by bonding them together into chains. Plants store glucose as starch. Animals store glucose as glycogen. Plants also use glucose to make cellulose, which strengthens stems, and branches.

20. Lipids are fats & oils

21. STEROIDS

22. PROTEINS are chains of amino acids

23. Proteins do important jobs in cells

27. Nucleic Acids are important information molecules

28. DNA is made of only four smaller molecules Imagine writing all the instructions to build & operate your body, using an alphabet with only four letters.