2Chemical Basis of Lifeprinciples of chemistry help to understand biologyorganisms are bags of chemicalsfunction of organisms & parts of organisms are determined byway chemicals are arrangedcompounds & molecules formed by chemicalsstructure determines functionStructure Functionlong handle to hold easiermade of wood to be strongblunt metal end to hit nailscurved, claws to pull out nails
3Chemistry chemicals give cells properties these properties are called lifeHierarchyChemicalsorganellescellstissuesorgansorganisms
4Matter all living things are made of matter anything that occupies space & has massmatter is composed of elements
5Elementssubstances which cannot be decomposed into simpler substances by chemical means92 naturally occurring elements25 elements are found in living things96%-H, O, C & N4%-Ca, P, K & STrace elements-Fe, Mg, Mn (manganese) & Iessentialcannot live without them
7Atoms elements are composed of atoms only one kind of atom for each elementsmallest units of matter that retainproperties of an element
8Sub-atomic Particles Protons Electrons Neutrons different elements have different numbers of sub-atomic particlesput together differently in different atomschemical & physical differences of elements are due to these differences
9Sub-Atomic Particles Protons found in nucleus of atom Neutrons one positive chargefound in nucleus of atomNeutronsno chargeElectronsone negative chargeorbit nucleus
10Periodic Tableatom’s structure determines how element it comprises forms compounds & moleculeskey to this can be found by knowing number of sub-atomic particles an element possessfound in Periodic Table of the Elements
11atomic number-number in upper left corner atomic weight or mass number-number located on bottomThe mass of any atom is approximately equal to the total number of its protons and neutrons multiplied by the atomic mass unit, u = gram.
12Atomic Number gives number of protons in atom Helium Atomic Number = 2 has 2 protons
13Mass Number number of neutrons + number of protons He = 4 variant forms of elements can existsome atoms of an element may have different mass numbersthese are isotopessame number of protons & electrons; different number of neutrons
14Number of Electrons net charge of atom = zero each proton has one positive chargeeach electron has one negative chargeneutrons have no chargeto be neural atom must have same number of electrons as protonsatom of helium with 2 protons has 2 electrons
15ChallengeQuestion How many protons does Sulfur have? How many electrons?Why?
17Chemical Propertiesarrangement of electrons determines chemical properties of atomelectrons orbit around nucleusfound at different energy levels-shellseach shell accommodates a specific number of electrons
18Electron Shells innermost shell-2 2nd & 3rd-8 number of electrons in outermost shell determines chemical properties of atomthose with shells that are not full will interact with other atoms & participate in chemical reactionsthose with full shells do not interact-inert
19Electron Shells H-one electron in outer most shell very reactive C, N, & Ohighly reactive since outer shells are incompleteHeinert or nonreactive-outer shell is full
20Challenge Question Is Chlorine reactive or not reactive? How can you tell?
21Atom Interactions-Chemical Bonds when atom with incomplete outer shell reacts with another atom with incomplete outer shell they can interact or form a bondShareDonateReceive electronsin this way both atoms can have a complete outer shell
22Types of Chemical Bonds Covalent Bondsshare electronsIonicgive or receive electrons
28In Class Exercise Pretend you are an atom Take the number of your birth month as your atomic numberDetermine the configuration of electrons in your valence shellFind another atom that you might interact with to form ions or new moleculesDemonstrate-draw on board
29Chemical Reactions elements combine to make molecules & compounds 2 H2 + O2 2H2O2 molecules of H react with one molecule of O (reactants) to form 2 molecules of water (product)arrow indicates direction of reactiontwo sides of equation on either side of arrow must balance
30Water single most important constituent of body life on Earth depends on unusual structure & nature of waterOrganisms consist mostly of water-2/3rds total body weight of humans.
31Importance of Water Organisms consist mostly of water 2/3rds total body weight of humansBiochemistry is a wet chemistrybiological molecules do not react chemically unless in solutionWater is an important reactantnearly all chemical reactions in body occur in waterFoods are digested to building blocks by decomposition reactions called hydrolysisinvolves addition of waterWhen large molecules form from smaller ones, water is removed in dehydration synthesis or condensation reactions
32Water Structure 2 H atoms attached covalently to one O2 molecule sharing of electrons is not equaloxygen pulls more on electrons than hydrogenelectrons spend more time near oxygen than hydrogenunequal sharing produces- polar bondbond in which two atoms involved have an equal pull on electrons-nonpolar
33Water StructureO2 attracts electrons more strongly than H-giving water an asymmetrical distribution of chargeresult-V-shapeH end has positive chargeOxygen end has negative chargewater has 2 poles-polarpolarity results in weak electrical attractions between neighboring water molecules
34Polarity of WaterPolarity results in weak electrical attraction between neighboring water moleculesslightly positive Hs in one water molecule attract slightly negatively charged O2 in another water moleculeopposite electrical charges attractwater molecules attract each othermaking water kind of stickythese weak attractions-hydrogen bondsweaker than covalent or ionic bonds
35Polarity, H Bonding & Water’s Properties cohesive natureability to moderate temperatureice floatinguniversal solvent propertiesCohesive Nature-water molecules attract eachclump together -cling or stick together to form films-surface tension. Water beads up into spheres when on hard surface. Important in living world-tress depend on this to help transport water from roots to leaves. Moderation of Temperature-High Heat Capacity-heat absorption-ability to absorb and retain heat. H bonding allows water to resist temperature changes. Temperature and heat-related-but different. Heat-amount of energy associated with movement of atoms and molecules in body of matter. Temperature-measure of intensity of heat-average speed of molecules rather than total amount of heat energy in body of matter. Example-swimmer in large body of water-may have higher temperature than water; water has more heat because of its immense volume. Heatwaterheat energy first disrupts H bonds-makes molecules move faster. Because heat first used to break bonds and not raise temperaturewater absorbs large amount of heat while only warming few degrees. Water has high specific heat index-can absorb lot of heat before begins to get hot. Why water is valuable to industries and in car radiators as coolant. High Heat of Vaporization-temperatures must be quite high before individual molecules have enough energy to break free and become water vapor-gaseous. Carries heat away with it as transforms from liquid to gas-cooling effect of perspiration-evaporative cooling. When substance evaporates-surface of liquid-what is remaining behind cools. Occurs because molecules with greatest energy-hottest ones-vaporize first. Globally-surface evaporation cools tropical oceans. Individually-prevents over heating. When water coolsremains liquid over wide range of temperatures-H bonds formreleases heat-water releases large amount of heat to surroundings while water temperature only drops few degrees. Freezing and boiling points far apart-freezes-32o F and boils-212o F. Unusually large amount of heat energy needed to change temperature of 1 gram of water by 1oC-once amount of water has reached particular temperature-changes temperatures only very slowly-thermal inertia-helps stabilize body temperatures. Large body of water can store huge amount of heat from sun. In coldheat given off from gradually cooling water can warm air-stabilizes ocean temperatures. Ice Floating-when most liquids cool molecules get closer and closerif cold enoughsolid. When water molecules coolmove apartice. Ice has fewer molecules than equal volume of liquid water less densefloats. Due to H bonding. H bonding lasts longer in ice; with each molecule bound to 4 neighbors. Ice is spacious crystal. Promotes life because if water behaved as other liquidsall water would freeze solid. When warming only upper few inches would thaw. When deep body of water coolsfloating ice insulates liquid water beneathlife persists. Universal Solvent-if substance dissolves in water-soluble-forms solution-uniform mixture of 2 or more substances. Solvent-medium in which other atoms, molecules or ions are dispersed. Dispersed substances-solutes. Water-powerful solvent-universal-dissolves more substances than any other liquid. Solution formed-aqueous solution. Fluids of lifeaqueous. Being soluble in water means that wherever water goes, through ground or through body-takes along with it chemicals, minerals, and nutrients. Useful as transport mechanism. Because of polar nature-water molecules orient themselves with slightly negative ends towards positive side of solutes and vice versa-first attracting and then surrounding them. Compounds formed by ionic bonds-ionize or dissociate-in water-broken as individual ions interact with either positive or negative end of water. Producing cations (+) and anions (-) surrounded by water molecules forming hydration sphere. Aqueous solution with anions and cations conducts electrical currents. Cations move to negative side having + change and anions move to positive side having– charge. Electrical forces across cells affects functioning of cells-muscle contraction and nerve function. Soluble inorganic molecules whose ions will conduct an electrical current in solution- electrolytes. NaCl-electrolyte. NaCl + H2ONa+ + Cl-. Changes in body fluid concentrations of electrolytes disturbs almost all vital functions. Decrease in K+ muscle paralysis; increaseweak, irregular heartbeats. Organic molecules have polar covalent bonds-attract water. Hydration shells form around large charged molecules-proteins-shielding them from effects of other charged substances and preventing them from settling out of solution. Hydration spheres carry them into solution. These mixtures are colloids-solutions of dispersed proteins or other large molecules which do not come out of solution-Jello. Particles remain in solution indefinitely. Suspension-contains even larger molecules that will if undisturbed settle out of solution due to gravity. Stirring sand in watersuspension lasts until sand settles bottom. Molecules that dissolve in water are hydrophilic-water loving-those that do not readily react with water-hydrophobic-have few if any polar, covalent bonds. These are non polar-when exposed to water-hydration spheres do not formmolecules do not dissolve. Body fat-large, insoluble droplets of hydrophobic molecules trapped in watery interior of cells.
36Dissociationcompounds formed by ionic bonds will ionize or dissociate in waterdissociation produces cations (+) & anions (-)aqueous solution containing anions & cations will conduct electrical currentscations move to negative side have + changeanions move to positive side having – chargesoluble inorganic molecules whose ions will conduct an electrical current in solution are electrolytesNaClNaCl + H2ONa+ + Cl-
37Acids & Bases H+ & OH- are in solution at all times H2O < > H+ + OH- -reversible reactionsome compounds add more hydrogen ionsothers remove themcompounds that donate hydrogen ions-acidHClH+ + Cl-acidic solution is one that has more H+ than OH-
38Acids & Bases compound that accepts or removes hydrogen ion is a base NaOHNa+ +OH-basic solution-one that has more OH- than H+
39pH scale pH = potential hydrogen scale developed-1909 by Dane Soren Sorensenbeer brewer looking for way to check acidity of beerdescribes how acidic or basic a solution isscale ranges from 0-140 = most acidic14 = most basic7=neutral
40pH at neutral pH H+ = OH- pH < 7 is acidic pH > 7 is basic or alkaline
41Buffers pH of blood ranges between 7.35-7.45 value must be maintained in narrow rangeeven small change can lead to severe metabolic consequencesbiological fluids contain bufferssubstances that resist changes in pH by accepting H+ when in excess & donating H+ when depleted