BIO 101 1st Edition Lecture 4 Outline of Last Lecture I Life Begins in Water II Examples of Unusual Properties of H2O a High specific heat b H2O expands when H freezes c Water is the Biological Solvent i Aqueous solutions III Solute Concentration IV Acids Bases and pH a Mathematical definition of pH Outline of Current Lecture I Carbon Element of Life II Carbon Skeleton III Isomers a Structural b Geometric c Optical IV Hydrocarbons Chapter 4 Carbon and Molecular Diversity Most biologically important molecules are carbon based Carbon 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 form CO2 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 of molecules that have different functions Organic molecules molecules that contain carbon organic Chemistry branch of chemistry that studies carbon compounds Properties of organic molecules depend on arraignment of carbon atoms in molecules CARBON SKELETON Variations 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 skeleton o All contribute to complexity and diversity of organic molecule BIO 101 1st Edition Isomers compounds with same molecular formula but different structures different structures mean different functions 3 Kinds 1 Structural isomers different in covalent arrangement of atoms 2 Geometric isomers same covalent bonds but differ in spatial arrangement Because of the rigid double bond will not allow rotation Subtle difference affects biological activity 3 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 protein o sugars only the D isomer is recognized Hydrocarbons 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 properties BIO 101 1st Edition behave consistently from one molecule to the next are usually involved in chemical reactions can be thought of as molecular accessories Six Major Functional groups Know names of groups structures and how they are attached to carbon skeleton except for phosphate and characteristics that are conferred by the group
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