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.