Chapter 2 The Chemistry of Life

2-1 The Nature of Matter Living things are made of chemical compounds Atom = the basic unit of matter - made of protons (positive), electrons (negative), and neutrons (neutral) - Atomic number = # of protons - Atomic mass = protons plus neutrons

Element = a pure substance that consists of just one kind of atom - Isotopes = atoms of the same element with different # of neutrons - example: carbon 12, 13, 14 - Isotopes have the same # of electrons so they have the same chemical properties

- Radioactive Isotopes – Have unstable nuclei and break down at a constant rate over time… used to determine age of rocks and fossils, treat cancer, and kill bacteria

Compound = two or more elements bonded in definite proportions. - example: H 2 O, NaCl Chemical Bonds – involves valance electrons

- Ionic bond = one or more electrons are transferred from one atom to another, then opposite charges attract two ions

- Covalent bond = electrons are shared between atoms - Molecule = when atoms are joined together by covalent bonds

- Van der Waals Forces = slight attraction between oppositely charged regions of nearby molecules

2-2 Properties of Water Water is the single most abundant compound in most living things. Properties - Water expands as it freezes… ice floats on liquid water

- Polarity – oxygen atom attracts shared electrons stronger than the hydrogen atoms - causes hydrogen bonds – attraction between slightly + and – - cohesion = attraction between molecules of same substance; allows beading of water and surface tension - adhesion = attraction between molecules of different substances; meniscus and capillary action Water properties website

Solutions and suspensions - mixture = two or more elements physically mixed - solution = mixture with evenly distributed molecules - solute = dissolved substance - solvent = substance in which solute is dissolved - suspension = mixtures of water and nondissolved material

Acids, Bases and pH - Water can split to form ions H 2 O  H+ + OH- the ions are equal so water is neutral

- pH scale = indicates the concentration of hydrogen ions (H+) - acids = form H+ ions in water; pH value lower than 7 - bases = form OH- ions in water; pH value higher than 7 - buffers = weak acids or bases that can react with strong acids or bases to prevent changes in pH

2-3 Carbon Compounds Carbon has four valence electrons and forms strong chains or rings Macromolecules means “giant molecules” - formed by a process of polymerization - monomers = small units which are joined to form polymers

- Carbohydrates = main source of energy and used for structure - made of carbon, hydrogen and oxygen, ratio 1:2:1 - monomers = sugars or monosaccharides; glucose - polymers = starches or polysaccharides; glycogen, cellulose

Starch Glucose

- Lipids = energy storage, insulation, makes up membranes - made of carbon, hydrogen and oxygen - examples: fats, oils, and waxes - saturated – no double bonds… butter - unsaturated – has double or triple bonds… olive oil - steroids – chemical messengers

- Nucleic acids = store and transmit hereditary information - made of hydrogen, oxygen, carbon, and phosphorus - monomers = nucleotides

- Proteins = control rate of chemical reactions, regulate cell processes, form bone and muscle, transport substances, fight diseases - made of nitrogen, carbon, hydrogen, and oxygen - monomers = amino acids; 20 different a.a. in nature

General structureAlanineSerine Amino groupCarboxyl group Amino Acid Structure

Proteins form certain structures Amino acids

2-4 Chemical Reactions and Enzymes Chemical reaction = process that changes, or transforms, one set of chemicals into another. - Equation: reactants  products

- Endothermic reaction = requires energy - Exothermic reaction = releases energy; can occur spontaneously - Activation energy = needed for most reactions to occur

Enzymes = proteins that act as biological catalysts, which speed up chemical reactions in the body… lowers activation energy - usually specific to reaction and not used up in reaction

- Enzyme-substrate complex = site where reactants are brought together to react; fit like a lock and key - Enzymes work in specific range of conditions: pH, temp