The Structure and Function of Macromolecules

II. Classes of Organic Molecules: What are the four classes of organic molecules?

I. Polymers What is a polymer? Poly = many; mer = part. A polymer is a large molecule consisting of many smaller sub-units bonded together. What is a monomer? A monomer is a sub-unit of a polymer.

A. Making and Breaking Polymers How are covalent linkages between monomers formed in the creation of organic polymers? Condensation or dehydration synthesis reactions. Monomers are covalently linked to one another through the removal of water.

Condensation Synthesis

Hydrolysis

1. Structure of Monosaccharides

Classified according to the size of their carbon chains, varies from 3 to 7 carbons. Triose = 3 carbonsPentose = 5 carbonsHexose = 6 carbons

In aqueous solutions many monosaccharides form rings:

2. Structure of Disaccharides Double sugar that consists of 2 monosaccharides, joined by a glycosidic linkage. What reaction forms the glycosidic linkage?

Examples of Disaccharides: Lactose = glucose + galactose Sucrose = glucose + fructose

3. Polysaccharides Structure: Polymers of a few hundred or a few thousand monosaccharides. Functions: energy storage molecules or for structural support:

B. Lipids Structure: Greasy or oily nonpolar compounds that are insoluble in water Functions :

1. Structure of Fatty Acids Long chains of mostly carbon and hydrogen atoms with a - COOH group at one end. When they are part of lipids, the fatty acids resemble long flexible tails.

Saturated and Unsaturated Fats Unsaturated fats : Saturated fats:

Saturated fatty acid

Unsaturated fatty acid

2. Structure of Triglycerides Glycerol + 3 fatty acids 3 ester linkages are formed between a hydroxyl group of the glycerol and a carboxyl group of the fatty acid.

3. Phospholipids Structure: Glycerol + 2 fatty acids + phosphate group.

Phospholipids in Water

4. Waxes Function: Lipids that serve as coatings for plant parts and as animal coverings.

5. Steroids Structure: Four carbon rings with no fatty acid tails Functions: Component of animal cell membranes Modified to form sex hormones

C. Proteins Structure: made of C.H.O, +N. Polypeptide chains Consist of peptide bonds between 20 possible amino acid monomers Have a 3 dimensional globular shape

1. Functions of Proteins

2. Structure of Amino Acid Monomers

Properties of Amino Acids Grouped by polarity Variable R groups (side chains) confer different properties to each amino acid:

3. Primary Structure Unique sequence of amino acids in a protein Slight change in primary structure can alter function Condensation synthesis reactions form the peptide bonds between amino acids

4. Secondary Structure Repeated folding of protein’s polypeptide backbone stabilized by H bonds between peptide linkages in the protein’s backbone 2 types, alpha helix, beta pleated sheets

5. Tertiary Structure Irregular contortions of a protein due to bonding between R groups Weak bonds: –H bonding between polar side chains –ionic bonding between charged side chains –hydrophobic and van der Waals interactions Strong bonds: –disulfide bridges form strong covalent linkages

Strong Bonds: Disulfide bridges form strong covalent linkages

5. Quaternary Structure Results from interactions among 2 or more polypeptides

Factors That Determine Protein Conformation Occurs during protein synthesis within cell Depends on physical conditions of environment –pH, temperature, salinity, etc. Change in environment may lead to denaturation of protein Denatured protein is biologically inactive Can renature if primary structure is not lost

D. Nucleic Acids Two kinds: –DNA: double stranded makes up genes which code for proteins –RNA: functions in actual synthesis of proteins coded for by DNA is made from the DNA template molecule

1. Nucleotide Monomer Structure Both DNA and RNA are composed of nucleotide monomers. Nucleotide = 5 carbon sugar, phosphate, and nitrogenous base Deoxyribose in DNARibose in RNA

2. Building the Polymer Phosphate group of one nucleotide forms strong covalent bond with the #3 carbon of the sugar of the other nucleotide.

3. Functions of Nucleotides Monomers for Nucleic Acids Transfer chemical energy from one molecule to another (e.g. ATP)

Summary of the Organic Molecules: