Four Major Classes of Macromolecules

Four major classes of macromolecules 1. 2. 3. 4. Carbohydrates Lipids Proteins Nucleic acids Organic molecules all contain carbon (may also contain hydrogen, oxygen, nitrogen, and some other minor elements) Monomers Individual subunits of macromolecules Polymers Monomers are linked together via covalent bonds into polymers Dehydration synthesis Two molecules of glucose are linked to form the disaccharide maltose A water molecule is formed as the two monosaccharides are linked by a covalent bond Hydrolysis Process of breaking polymers down into individual monomers, AKA dehydration reaction Water serves as a reactant; one monomer receives a H+ and the other monomer receives an OHEnzymes Are biological molecules that catalyze or “speed up” reactions Chemical reactions involving macromolecules are catalyzed by enzymes Enzymes speed up hydrolysis and dehydration reactions ➢ Dehydration reactions form new bonds/require energy ➢ Hydrolysis reactions break bonds/release energy Specific enzymes exist for each macromolecule class ➢ Carbohydrates- broken down by amylase, sucrose, lactase, maltase ➢ Lipids - broken down by lipases ➢ Proteins - broken down by pepsin and peptidase Carbohydrates Found in grains, fruits, and vegetables Provide energy to body in form of glucose Represented by the general formula (CH2O)n Ratio of Carbon: Hydrogen: Oxygen is 1:2:1 Has 2 main subtypes: 1. Monosaccharides 2. Disaccharides 3. Polysaccharides Monosaccharides Usually have 3-7 carbons End with the suffix -ose Contains a carbonyl group C=O Aldoses: carbonyl group at the end of the carbon chain Ketoses: carbonyl group in the middle of the carbon chain Trioses: three carbons Pentoses: five carbons Hexoses: six carbons Three structural isomers of a hexose monosaccharide Structural isomers/formula (C6H12O6) 1. Glucose - important source of energy 2. Galactose - part of lactose/milk sugar 3. Fructose - part of sucrose/fruit Monosaccharides exist as linear chain or ring-shaped molecules o Five- and six-carbon monosaccharides exist in equilibrium between linear and ring forms o Ring forms and the side chains closes and is locked into an alpha or beta position o Fructose and ribose also form rings o They form five-member end rings as opposed to the six-membered ring of glucose Disaccharides Form when two monosaccharides are linked in a dehydration reaction Example: Glucose + Fructose = sucrose (disaccharide) Two monomers are joined by glycosidic bond Water is also released Carbon atoms in a monosaccharide are numbered from the terminal carbon closest to the carbonyl group o Glycosidic linkage is formed between carbon 1 in glucose and carbon 2 in fructose o Results in 1,2 glycosidic linkages o o o o Other common disaccharides Maltose (grain sugar) Lactose (milk sugar) Sucrose (table sugar) All are created via formation of covalent glycosidic linkages Polysaccharides Long chain of monosaccharides joined by glycosidic linkages May be branched or unbranched May consist of multiple layers of monosaccharides Molecular weight could be >10,000 Daltons Polysaccharides can be distinguished by their glycosidic linkages Starch is composed of Amylose and Amylopectin The monomers are joined in two linkage types: 1. α 1-4 glycosidic bonds 2. α 1-6 glycosidic bonds Amylose = unbranched glucose monomers in α 1-4 glycosidic bonds Amylopectin = branched glucose monomers in α 1-4 and α 1-6 glycosidic bonds Cellulose A polysaccharide found in the cell wall of plants Glucose monomers are linked in unbranched chained by β 1-4 glycosidic linkages Every glucose monomer is flipped relative to the next one resulting in a linear, fibrous structure Chitin The hard exoskeleton of arthropods is composed of the polysaccharide chitin Contains nitrogen Lipids Are a diverse group of non-polar hydrocarbons Non-polar hydrocarbons are hydrophobic Function of Lipids Long-term energy stores Provides insulation from environment for plants and animals Serve as building blocks for some hormones Important component of cellular membranes Types of Lipids Fats Oils Waxes Phospholipids