Biology I Chapter 4 - Professor Joni Balmgarden PDF

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Professor Joni Balmgarden...

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Section 4.1 Carbon the Basis of Biological Molecules

Section 4.2 Carbon Bonding - Carbon has 6 electrons o 4 Valance Electrons - Carbon tends to fill its valance by sharing its 4 electrons so 8 electrons are present in the valance shell o In organic molecules carbon usually forms single or double covalent bonds o Each carbon atom acts as an intersection point from which a molecule can branch off in up to four directions  Allows carbon to form very complex molecules

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Carbon has 3 main bonding partners Hydrogen, Oxygen and Nitrogen

The electron configuration of carbon gives it covalent compatibility with many different elements Molecular Diversity Arising from Variation in Carbon Skeletons - Carbon skeletons vary in length and may be straight, branched or arranged in closed rings o Important for the diversity of life Hydrocarbons - Hydrocarbons – Organic molecules consisting of only carbon and hydrogen -

o Hydrogen atoms are attached to the carbon skeleton wherever electrons are available for covalent bonding  Major components of petroleum - Hydrocarbons are not prevalent in most living organisms - Fats have long hydrocarbon tails attached to a nonhydrocarbon component o Makes them hydrophobic because the great majority of their bonds are relatively nonpolar carbon-to-hydrogen linkages - Hydrocarbons can undergo reactions that release a relatively large amount of energy. o Gasoline, fuel for plant seeds Isomers - Isomer – Compound that have the same number of atoms of the same elements but different structures and hence different properties - Structural Isomers – Isomers that differ in the covalent arrangements of their atoms - The number of possible isomers increases tremendously as carbon skeletons increase in size

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Cis-trans Isomers – Carbons have covalent bonds to the same atoms, but these atoms differ in their spatial arrangements due to the inflexibility of double bonds. o Double bonds do not permit rotation of atoms

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Enantiomers – Isomers that are mirror images of each other and that differ in shape due to the presence of an asymmetric carbon o “Right-handed / Left-handed” versions of a molecule o Usually, only one isomer is biologically active because only that form can bind to specific molecules on an organism o Important concept in the pharmaceutical industry  Two enantiomers of a drug may do two very different things

Most Important Chemical Groups to Life Functional Groups – A specific configuration of atoms commonly attached to the carbon skeletons of organic molecules and involved in chemical reactions Seven Chemical Groups most Important in Biological Processes o Hydroxyl o Carbonyl o Carboxyl o Amino o Sulfhydryl o Phosphate o Methyl First six groups can be chemically reactive o Of those 6, all but Sulfhydryl are hydrophilic and thus increases the solubility of organic compounds in water o The Methyl group is not reactive, but instead often serves as a recognizable tag on biological molecules

ATP - Adenosine Triphosphate (ATP) – An Adenosine bonded to three phosphates that releases free energy when its phosphate bonds are hydrolyzed o Used as fuel by cells...