3-2: MOLECULES OF LIFE There are 4 classes of organic compounds essential to life: Carbohydrates Proteins Lipids Nucleic Acids Each of these compounds are made up of C, H, + O atoms; but occur in different ratios

Carbohydrates Organic compounds composed of C, H, + O Found in ratios of 2H:1O; the # of C varies

Carbohydrates (cont.) Monosaccharides Monomer – a simple sugar (1C:2H:1O ratio) Formula = (CH2O)n ; where n = 3-8 Common types: Glucose - - used in cells Fructose - - found in fruits Galactose - - found in milk All have same formula = C6H12O6 Isomers = same formula, different structures

Examples

Carbohydrates (cont.) Disaccharide – “double sugar” – combination of 2 monosaccharides from a condensation rxn Ex. Sucrose

Carbohydrates (cont.) Polysaccharide – complex molecules composed of 3 or more monosaccharides In animals, glucose is stored as glycogen Found in branched chains Stored in liver + muscles

Carbohydrates (cont.) In plants, glucose is stored as starch or cellulose Starch – found as branched or unbranched chains Cellulose – gives strength + rigidity to plant cell walls

Proteins Organic compounds composed mainly of C, H, O, + N Formed from monomers Found in skin, hair, nails + muscles

Proteins (cont.) Amino Acids (AA) Building blocks of proteins – monomer 20 different AA in living things Difference = functional groups attached to C R. Groups can be simple or complex Can take on a variety of shapes, thus carrying out different activities in living things

Proteins (cont.) Dipeptide – the bonding of 2 AAs Forms a peptide bond

Proteins (cont.) Polypeptide – a long chain of AA’s Chain folds or bends based on certain conditions ( i.e. Temperature increase/decrease) – ex. egg When polypeptide folds, takes on a globular shape

Proteins (cont.) Enzymes RNA or protein molecules that act as biological catalysts Work by a “lock-and-key” method with its substrate – the reactant being catalyzed Substrate will only “fit” if shape of active site is a match Once enzyme is done, it releases the product(s) and can be used over + over again Mail fail to work if environment changes (temp or pH)

How an enzyme works…

Lipids Large, nonpolar organic molecules that do not dissolve in water Higher ratio of C + H atoms to O atoms C-H bonding (stores more nrg)

Lipids (cont.) Fatty acids – monomer of a lipid – unbranched chains Contain a carboxyl group, -COOH, at one end Hydrophilic end – attracted to water (polar) Hydrocarbon at other end Hydrophobic end – “afraid” of water (nonpolar)

Saturated vs. Unsaturated Saturated – all C atoms are “full” Unsaturated – has double bond(s) between C atoms

Lipids (cont.) Triglyceride – 3 fatty acid molecules + glycerol Functions: NRG, insulation + protection, nutrition (vitamins ares stored in fats in body) Types: Saturated High melting point, solid @ room temp. Examples: shortening (Crisco), animal fats Unsaturated Low melting point, liquid @ room temp. Examples: plant seed oils, fruits

Lipids (cont.) Phospholipids – 2 fatty acid molecules + glycerol Forms lipid bilayer for cell membranes

Lipids (cont.) Wax – long fatty acid chain + long chain of alcohol Highly waterproof Used as a protective coating

Lipids (cont.) Steroids – molecules of 4 fused C-rings with different functional groups Common types: Hormones – testosterone Cholesterol – needed by nerves + cells

Nucleic Acids Very large, complex organic molecules that store important information in cells Two types: DNA – deoxyribonucleic acid – determines characteristics of organism and directs cells activities RNA – ribonucleic acid Stores + transfers info. essential to make proteins Can also act as an enzyme Nucleotides – monomers of Nucleic Acid 5-C sugar Phosphate group Nitrogen-base

What a nucleotide looks like…

DNA vs. RNA