BIO 101 1st EditionLecture 4Outline of Last LectureI. Life Begins in WaterII. Examples of Unusual Properties of H2Oa. High specific heatb. H2O expands when H freezesc. Water is the Biological Solventi. Aqueous solutionsIII. Solute ConcentrationIV. Acids, Bases and pHa. Mathematical definition of pHOutline of Current LectureI. Carbon-Element of LifeII. Carbon SkeletonIII. Isomersa. Structuralb. Geometricc. OpticalIV. HydrocarbonsChapter 4- Carbon and Molecular DiversityMost biologically important molecules are carbon-basedCarbon- element of life why carbon?- Small, forms strong bonds (4 covalent bonds)- Versatility in bonding: can bond to other carbon atoms or to several other elements- Good transport formCO2= carbon dioxide is a gas that easily crosses membranes (contrast with SiO2=sand)- Thus, carbon can form large complex and diverse molecules- this is important for living things. Carbon can be used to make many kinds ofmolecules that have different functions.Organic molecules= molecules that contain carbon/organicChemistry= branch of chemistry that studies carbon compoundsProperties of organic molecules depend on arraignment of carbon atoms in molecules= CARBON SKELETONVariations in Carbon Skeleton- Length (how many carbon atoms)- Shape=straight chain, branched chain, ring- Location and number of double bonds- What other elements covalently bonded to skeletono All contribute to complexity and diversity of organic moleculeBIO 101 1st EditionIsomers= compounds with same molecular formula but different structures (different structures mean different functions)3 Kinds1. Structural isomers= different in covalent arrangement of atoms2. Geometric isomers= same covalent bonds but differ in spatial arrangement- Because of the rigid double bond, will not allow rotation- Subtle difference affects biological activity3. Optical isomers(stereoisomers)= isomers that are mirror images of each other- Optical isomers occur whenever there are 4 different atoms or groups of atoms bonded to the same carbon atom- A carbon with 4 different atoms called asymmetric- The 4 different groups can be arranged in space in 2 different ways that are mirror images of each other (can’t superimpose) - Speak of left or right-handed isomers (or D and L isomers)- Usually only one of the forms is biologically active - Examples of optical isomers: o amino acids- only the L isomer is used to make proteino sugars- only the D isomer is recognizedHydrocarbons= molecules containing only C and H- major components of fossil fuels- hydrocarbon are nonpolar (hydrophobic) and therefore don’t dissolve in water (because H2O is polar)- hydrocarbons are nonpolar because the bonds between C and H are nonpolar covalent bonds (because electronegativity of C and H is about the same)Functional groups= specific groups of atoms bonded to the carbon skeleton- each functional group confers specific chemical and physical propertiesBIO 101 1st Edition- behave consistently from one molecule to the next- are usually involved in chemical reactions- can be thought of as molecular accessoriesSix Major Functional groupsKnow names of groups, structures, and how they are attached to carbon skeleton (except for phosphate), and characteristics that are conferred by the
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