Chapter 2 The Chemistry of Life

Atoms Atoms are the smallest part of matter Made up of Protons – Positive charge, found in nucleus Neutrons – no charge, found in nucleus Electrons – Negative charge, found outside the nucleus

Determining atomic number, atomic weight and neutrons Atomic number is the number of protons in the atom Atomic weight is the sum of the mass of the protons, neutrons, and electrons in an atom Number of neutrons can be determined by subtracting the atomic number from the atomic mass (rounded).

Electron shell model

Electron placement Bohr atom vs. modern interpretation

Compounds and molecules Compound - two or more elements chemically combined; Hydrogen and Oxygen combine to form water Molecule - smallest unit of a compound that retains the properties of the compound; H2O

B. Chemical Bonding

1. Ionic bonding 2. Covalent bonding 3. Hydrogen bonding Giving away or taking of electrons Ionic bond formation in sodium chloride 2. Covalent bonding Sharing of electrons Covalent bond formation in methane 3. Hydrogen bonding formed by the attraction of oppositely charged poles of molecules. Example in water; a weak bond

Properties of Water Because of the hydrogen bonds between water molecules, water is “sticky” Cohesion – Water sticks to itself (penny lab) Adhesion – Water sticks to other surfaces (capillary action, wet)

4. Chemical reactions 5. Acids and bases Chemical reaction - process in which atoms or molecules interact and form new bonds. Can be characterized by release or taking in of heat, color change, gas, etc. 5. Acids and bases Acids have a pH below 7, sour tasting and turn litmus paper red Bases have a pH above 7, taste bitter, and turn litmus paper blue

pH Scale

C. Major Organic Compounds of Living Things

1. Carbohydrates 2. Lipids Composed of carbon, hydrogen, and oxygen Monosaccharides, disaccharides, and polysaccharides Important as a food source 2. Lipids Fats; found in cell membranes, steroids Used for energy storage Generally do not dissolve in water

3. Proteins 4. Nucleic acids Composed of long chains of amino acids Include enzymes and structural materials Primary, secondary, and tertiary protein structure; can be denatured 4. Nucleic acids Composed of a sugar, phosphate and nitrogenous bases Bases: Adenine, Guanine, Cytosine, Thymine, Uracil Hereditary material

Enzymes Special proteins that speed up and control chemical reactions Usually named after the substances they act upon Often end in –ase Catalase, Lactase, Ribonuclease, etc. Animation

Enzymes lower acivation energy

Enzymes Lower the amount of energy needed for a reaction to proceed Are not used up during the reaction, and can be used over and over again Control your body’s metabolism (all chemical reactions in your body) Are affected by heat, temperature, and pH, they can be denatured (destroyed)