Campbell Biology 10th Edition Fall 2015 UCONN BIOL 1107 Unit 1 Chapter 4 Carbon and the Molecular Diversity of Life Key Concepts four other atoms 4 1 Organic chemistry is the study of carbon compounds 4 2 Carbon atoms can form diverse molecules by bonding to 4 3 A few chemical groups are key to molecular function Carbon The Backbone of Life Living organisms are made up of chemicals based mostly on the Carbon enters the biosphere through plants and other element carbon photosynthetic organisms large complex and varied Carbon is unparalleled in its ability to form molecules that are Carbon counts for the enormous variety of biological molecules Concept 4 1 Organic Chemistry is the Study of Carbon Compounds 1 Compounds containing carbon are said to be organic and their study is called organic chemistry a 1828 Friedrich Wohler a German chemist tried to make an inorganic salt ammonium cyanate by mixing solutions of ammonium ions NH4 CNO i Ended up making urea an organic compound present and cyanate ions in the urine of animals b Organic chemistry was redefined as the study of carbon compounds regardless of origin 2 Organic Molecules and the Origin of Life on Earth a 1953 Stanley Miller brought the abiotic synthesis of organic compounds into the context of evolution i Miller concluded that complex organic molecules could arise spontaneously under conditions thought at that time to have existed on the early Earth b The overall percentages of the major elements carbon hydrogen oxygen nitrogen sulfur and phosphorous are quite uniform across all organisms reflecting the common evolutionary origin i Because of carbon s ability to form four bonds the limited assortment can build inexhaustible variety of organic molecules c The great diversity of life on Earth also seen in fossils is all made possible by the unique versatility of carbon Concept 4 2 Carbon atoms can form diverse molecules by bonding to four other atoms The key to an atom s chemical characteristics is its electron configuration 1 The Formation of Bonds with Carbon a Carbon has 6 electrons with four valence electrons in its valence shell b In organic molecules carbon usually forms single or double covalent bonds c When a carbon atom forms four single covalent bonds the arrangement of its four hybrid orbitals causes the bonds to angle towards the corners of an imaginary tetrahedron d The bond angles in methane CH4 are 109 5 degrees which is roughly the same in any group of atoms where carbon has four single bonds e When two carbon atoms are joined by a double bond like ethene C2H4 the bonds from both carbons are all in the same plane so the atoms joined to those carbons are in the same plane as well f The shape of the molecule is central to its functions g The electron configuration of carbon gives it covalent compatibility with many different elements h Because CO2 is a simple molecule and lacks hydrogen it is often considered inorganic i Whether we call carbon dioxide organic or inorganic it s clearly important to the living world as a source of carbon for all organic molecules in organisms 2 Molecular Diversity Arising from Variation in Carbon Skeletons a Hydrocarbons i Organic molecules consisting of only carbon and hydrogen are called hydrocarbons ii The molecules known as lipids have long hydrocarbon tales attached to a non hydrocarbon component iii Petroleum and fat don t dissolve in water because their hydrophobic compounds have relatively nonpolar carbon to hydrogen bonds iv Hydrocarbons can undergo reactions that release a relatively large amount of energy i Compounds that have the same numbers of atoms of the same elements but different structure hence different properties are isomers b Isomers 1 There are three different types of isomers a Structural isomers b Cis trans isomers c Enantiomers ii Structural isomers differ in covalent arrangements of their atoms iii In cis trans isomers formerly called geometric isomers carbons have covalent bonds to the same atoms but they differ in their spatial arrangements due to inflexibility of double covalent bonds iv Enantiomers are isomers that mirror each other but differ in shape due to the presence of an asymmetric carbon Concept 4 3 A few chemical groups are key to molecular function 1 The Chemical Groups Most Important in the Processes of Life a Chemical groups are directly involved in chemical reactions known as functional groups b The seven chemical groups most important in biological processes are i Hydroxyl polar due to electronegative oxygen ii Carbonyl ketone or aldehyde iii Carboxyl acts as an acid iv Amino can pick up H from surrounding solution v Sulfhydryl vi Phosphate vii Methyl c The red groups first six can be chemically reactive and all of them besides the sulfhydryl are hydrophilic and increase the solubility of organic compounds in water d The methyl group is not reactive but serves as a recognizable tag on biological molecules 2 ATP An Important Source of Energy for Cellular Processes a Adenosine triphosphate or ATP consists of an organic molecule called adenosine which is attached to a string of three phosphate groups b Though ATP is thought of to store energy it s more like its storing the potential to react with water 3 The Chemical Elements of Life A Review a Living matter consists mainly of carbon oxygen hydrogen and nitrogen with smaller amounts of sulfur and phosphorous b Carbon is the virtuoso of the covalent bond