Biochemistry Chapter 4 Functional Groups
Carbon—The Backbone of Biological Molecules • All living organisms are made up of chemicals based mostly on carbon due to its bonding ability
Chapter 4 • Organic chemistry • the study of carbon compounds • Organic compoundshave carbon in them (& usually H) • Exception: CO2 is considered INORGANIC • Range from simple (ie. methane, CH4) to complex molecules (ie. proteins)
Stanley Miller’s Experiment • Gave support against the concept ofvitalism • idea that organic compounds arise only within living organisms • disproved when chemists (such as Miller) synthesized carbon compounds in lab • Thoughts shifted from vitalism to mechanism • the view that all natural phenomena are governed by physical and chemical laws.
Stanley Miller’s Experiment Gases CH4, NH3, H2O, H2 (thought to be found in the primitive atmosphere) Simulated lightning
Formation of Bonds w/ Carbon • Carbon atoms • have 4valence electrons which can bond to 4 other atoms, forming diverse molecules • Carbon has bonding versatility • It can bond with four other atoms to form diverse molecules, including with hydrogen to form hydrocarbon chains • can form 4 covalent bonds with itself or other atoms very important in living things!
Hydrogen (valence = 1) Oxygen (valence = 2)) Nitrogen (valence = 3) Carbon (valence = 4)) H O N C Figure 4.4 • The electron configuration of carbon gives it covalent compatibilitywith many different elements • Carbon often bonds covalently to the following molecules, forming an organic molecule: (Valence= # of covalent bonds an atom can form)
Molecular Diversity Arising from Carbon Skeleton Variation • Carbon chains • Form the skeletons of most organic molecules • Vary in length and shape • Straight • Branched • Rings
Hydrocarbons • Organic molecules consisting of only C and H • Ex: petroleum • Found in many of a cell’s organic molecules • Ex: phospholipid molecules in cell membranes • The covalent bonding btwn C-H is nonpolar (hydrophobic) fats and petroleum will not dissolve in water • High energy storage release a lot of energy when broken down
Fat droplets (stained red) 100 µm (b) Mammalian adipose cells (a) A fat molecule Figure 4.6 A, B Example of a Hydrocarbon
ISOMERS Isomers • Compounds with the same molecular formula, but different structure & properties • Have same # of atoms arranged differently 3 types of isomers • structural~ differ in covalent arrangements of their atoms Both of the above molecules are pentane (C5H12)
2. geometric~ differ in spatial arrangement • Arise from inflexibility of double C bond • cis (“X’s” same side of double C bond) vs. trans (“X’s” opposite sides of doube C bond) • X’s represents an atom or group of atoms Cis vs. trans
3. enantiomers~ mirror images of each other • used in pharmacological industry • The “asymmetrical carbon” is the middle carbon attached to four different atoms or groups of atoms 1 usually active; other inactive Asymmetrical Carbon
L-Dopa (effective against Parkinson’s disease) D-Dopa (biologically inactive) Figure 4.8
Functional Groups • Functional groups • parts of organic molecules involved in chemical rxns (chemically reactive groups) • replace a hydrogen bonded to a hydrocarbon • A given functional group will behave the same way regardless of which organic molecule it is bonded to. (display consistent behavior)
# & arrangement of functional groups helps give organic molecules unique, distinctive chemical properties • Each GROUP is HYDROPHILIC increases organic molecule’s solubility in water