General Biology/Getting Started/Chemical Building Blocks of Life

Building blocks of life Carbon based: organic molecules Carbohydrates: CHO Lipids: CHO, water insoluble Proteins: CHONS, structure/function in cells Nucleic acids: CHONP, hereditary (genetic) information Carbon Can make 4 covalent bonds Chains Straight Branched Ring Hydrocarbons (C, H): store energy Functional groups Attach to carbon Alter chemical properties Form macromolecules Sapoteton Carbohydrates Principally CHO (rare N, S and P) 1C:2H:1O ratio Energy rich (many C-H bonds) Monosaccharides (principal: glucose) Simple sugars Principle formula: C6H12O6 Form rings in water solution Disaccharides (sucrose, lactose) Polysaccharides (starch, glycogen, cellulose, chitin) Stereoisomers Bond angles of carbon point to corners of a tetrahedron When 4 different groups are attached to a carbon, it is asymmetric, leading to various types of isomerism Stereoisomers: (D, L) Same chemical properties Different biological properties D sugars, L amino acids Lipids C-H bonds (nonpolar) instead of C-OH bonds as in carbohydrates High energy Hydrophobic (insoluble in water) Categories Fats: glycerol and three fatty acids Phospholipids: primary component of membranes Prostaglandins: chemical messengers (hormones) Steroids: membrane component; hormones Terpenes: pigments; structure Fatty acids Hydrocarbon chain Even number of C, 14->20 Terminates in carboxyl group Saturated: contain maximum number of hydrogens (all single bonds); maximum energy Unsaturated: one or more double bonds Usually higher melting point Many common oils are polyunsaturated Proteins Polymer of amino acids 21 different amino acids found in proteins Sequence of amino acids determined by gene Amino acid sequence determines shape of molecule Linked by peptide bond (covalent) Functions regulate chemical reactions and cell processes [enzymes] form bone and muscle; various other tissues facilitate transport across cell membrane [carrier proteins] fight disease [antibodies] Motifs: folding patterns of secondary structure Domains: structural, functional part of protein often independent of another part; often encoded by different exons Shape determines protein's function Amino acids 21 commonly found in proteins 21st is selenocysteine, not mentioned in text Common structure Amino group: NH2 Carboxyl group: COOH R group- 4 different kinds of R groups acidic basic hydrophilic (polar) hydrophobic (nonpolar) Confer individual properties on amino acids List of amino acids Structure Primary structure: the amino acid sequence Determines higher orders of structure Critical for structure and function of protein Secondary: stabilized by intramolecular hydrogen bonding helix sheet Tertiary: folding, stabilized by ionic bonds (between R groups), hydrogen bonding, van der Waal's forces, hydrophobic interactions Quaternary: _ 2 polypeptides Function Requires proper folding, cofactors, pH, temperature, etc. Proteins are often modified after synthesis Chemical modification Addition of heme groups (hemoglobin, cytochrome) Denatured proteins can not function properly Proteins are degraded by proteosome as part of constant turnover of cell components Hereditary (Genetic) information Nucleic acids DNA: deoxyribonucleic acid Hereditary information of all cells Hereditary information for many viruses RNA: ribonucleic acid Hereditary information of certain viruses (HIV) Intermediate in gene expression Composed of nucleotides Ribonucleotides Deoxyribonucleotides RNA DNA origin Which came first? Paradox: DNA encodes protein necessary for its own replication Discovery of catalytic RNA by Cech and Altman suggested that RNA might have been first self-replicating molecule DNA evolved as more stable type of storage molecule Proteins: Their building block is amino acids. The bond connecting 2 of the amino acids together are called peptide bonds. One of these bonds makes a monopeptide, two a dipeptide, and any more than that makes a polypeptide. References This text is based on notes very generously donated by Dr. Paul Doerder, Ph.D., of the Cleveland State University.