Chapter 22.1 Atomic Structure is the Basis for Life's Chemistry1) Matter composed of atomsa) Each atom consists of positive charged nucleus ade up of protons and neutronsb) Surrounded by electrons bearing negative charges2) Mass of proton/neutron is one dalton=1.7x10-24 grams3) Mass of electron=0.0005 Da=9x10-284) Element is pure substance that contains only one kind of atoma) # of protons in nucleus defines element5) Most organisms composed ofa) Carbonb) Hydrogenc) Nitrogend) Oxygene) Phosphorusf) Sulfur6) Atomic number= # of protons7) Mass number= protons+neutrons8) Electron shellsa) First shell: two electronsb) Second and greater: eight electrons9) Molecules:two or more atoms bonded together2.2 Atoms interact and form molecules 10) Ionic bondsa) Form when atoms gain or lose one or more electrons to achieve stabilityb) Ion is electrically charged particle that forms when an atom gains or loses one or more electronsi) Cations: positive charge ionii) Anions: negative charged ionc) Ionic bonds (form when ions with opp. Charges attract) result in stable molecules that are often referred to as salti) Ionic attractions are weak, salts dissolve in water11) Covalent bonda) Sharing one or more pairs of electronsb) Important aspects of covalent bondsi) Orientation(1) give molecules their 3-d geometry and shapes of molecules contribute to biological functionsii) strength and stability(1) very strong therefore lots of energy to break themiii) multiple covalent bonds(1) single/double/triple bondsiv) degree of sharing electrons(1) attractive force an atomic nucleus exerts on electrons in a covalent bond is electronegativity(a) electronegativity depends on how many protons molecule hasv) Polar covalent bond: electrons drawn to one nucleus more than the other(1) Oxygen has slightly negative charge in H20 (delta negative)12) Hydrogen bondsa) May form between hydrogen (δ+) and strongly electronegative atom (δ-)b) contributes two properties of water:i) Heat capacity(1) Raising them of liquid water takes a lot of heat(2) High heat of vaporization (a lot of heat required to change water from liq. To gas)ii) Cohesion(1) capacity of water to resist coming apart from one another when placed under tension13) Polar molecules are hydrophilic (water loving)a) in aqueous solutions these molecules become separated and surrounded by water molecules14) Nonpolar molecules are hydrophobic (water hating)a) weaker bonds and cause nonpolar substances to aggregate15) Functional groupsa) Has specific chemical properties, and when attached to larger molecule, give those properties tolarger moleculesb) One propery is polarityc) Determine molecular shape and reactivity16) Macromolecules: large molecules formed by covalent linkages of smaller moleculesa) Formed by condensation rxns, that link together monomers containing particular functional groupsb) Four kinds are characteristic of living thingsi) Proteins(1) formed from different combinations of 20 amino acids, all of which share chemical similaritiesii) carbohydrates(1) formed by linking together chemically similar sugar monomers (monosaccharides) to form polysaccharidesiii) nucleic acids(1) formed from four kinds of nucleotide monomers linked together in long chainsiv) lipids(1) noncovalent forces maintain the interactions between lipid monomersc) With exception of lipids, all are polymers constructed by covalent bonding of smaller molecules called monomersi) polymers broken down by seiries of reactions involving water(1) condensation: removal of water links monomers together(2) hydrolysis: addition of water breaks polymer into monomers2.3 Carbohydrates consist of sugar molecules17) Carbohydrates general formula Cn(H2O)n18) Carbohydrates have four major biochemical rolesa) They are a source of stored energy that can be released in a form usable by organismsb) They are used to transport stored energy within complex organismsc) They function as structural molecules that give many organisms their shapesd) They serve as recognition or signaling molecuels tat can trigger specific biological responses19) Monosaccharides are simple molecules with up to seven carbon atomsa) Pentoses are five-carbon sugarsb) Hexoses (six carbon sugars) all have formula C6H12O6i) Include glucose, fructose,mannose, and galactosec) Disaccharides,oligosaccharides, and polysaccharides are all constructed from monosaccharidesthat are covalently bonded by condensation reactions that form glycosidic linkagesi) a single glycosidic linkage between two monosaccharides forms a disaccharideii) polysaccharides contain long chains of monomersd) Oligosaccharides contain several monosaccharides bound together by glycosidic linkages20) Polysaccharidesa) Large polymers of monosaccharides connected by glycosidic linkagesb) Starches comprise a family of molecules that are all polysacharides of glucosei) principal energy storage of plantsc) Glycogen is water-insoluble, highly branched polymer of glucosei) major energy storage molecule in mammalsd) Cellulose is most abundant carbon-containing biological compound on earthi) polysaccharide of glucose, but much more stable molecule than starch2.4 Lipids Are Hydrophobic Molecules21) Lipids are hydrocarbons and are insoluble in water because of nonpolar covalent bondsa) Have several roles in living organismsi) Store energy in C-C and C-H bondsii) Structural roles in cell membranes and on body surfacesiii) Thermal insulation22) Common units are triglycerides, AKA simple lipidsa) If solid at room temp. (around 20 degrees Celsius) are called fatsb) If liquid at room temp. called oilsc) Contains three fatty acid molecules and one glycerol moleculei) Glycerol is small molecule with three hydroxyl groups, therefore an alcohold) Fatty acid consists of long nonplar hydrocarbon chain attached to a polar carboxyl group, therefore a carboxylic acidi) Saturated fatty acid(1) all bonds between carbon atoms in hydrocarbon chain are single(2) no double bonds(3) Molecules rigid and straight and are packed tightlyii) Unsaturated fatty acid(1) Hydrocarbon chain contain one or more double bonds(2) Have kinks in the chain due to double bonds preventing molecules from being packed together tightly, low melting points, and are liquid at room temp.iii) Fatty acid has hydrophilic end and long hydrophobic tail(1) Two opposing chemical properties called amphipathic (both polar and nonpolar ends)e) Phospholipids: two fatty acids and a hydrophilic, phosphate-containing polr group