The Structure and Function of Macromolecules

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

•

What is a hydrolysis reaction?

• Polymers are broken down into monomers.

• Hydro = water; lysis = loosening/ • Water is added and the lysis of the polymer occurs.

Hydrolysis

II. Classes of Organic Molecules:

•

What are the four classes of organic molecules?

• Carbohydrates • Lipids • Proteins • Nucleic Acids

A. Carbohydrates

• Sugars • Carbo = carbon, hydrate = water; carbohydrates have the molecular formula (CH 2 O) n • Functions: • Store energy in chemical bonds • Glucose is the most common monosaccharide • Glucose is produced by photosynthetic autotrophs

1. Structure of Monosaccharides

• An OH group is attached to each carbon except one, which is double bonded to an oxygen (carbonyl).

• Classified according to the size of their carbon chains, varies from 3 to 7 carbons.

Triose = 3 carbons Pentose = 5 carbons Hexose = 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?

• Condensation synthesis

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:

• Starch is a plant storage from of energy, easily hydrolyzed to glucose units • Cellulose is a fiber-like structureal material - tough and insoluble - used in plant cell walls • Glycogen is a highly branched chain used by animals to store energy in muscles and the liver.

• Chitin is a polysaccharide used as a structural material in arthropod exoskeleton and fungal cell walls.

B. Lipids

• Structure: Greasy or oily nonpolar compounds • Functions: • Energy storage • membrane structure • Protecting against desiccation (drying out). • Insulating against cold.

• Absorbing shocks. • Regulating cell activities by hormone actions.

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 : – liquid at room temp – one or more double bonds between carbons in the fatty acids allows for “kinks” in the tails – most plant fats • Saturated fats: – have only single C-C bonds in fatty acid tails – solid at room temp – most animal fats

Saturated fatty acid

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.

• Function: Main structural component of membranes, where they arrange in bilayers.

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: • Polypeptide chains • Consist of peptide bonds between 20 possible amino acid monomers • Have a 3 dimensional globular shape

1. Functions of Proteins

• Enzymes which accelerate specific chemical reactions up to 10 billion times faster than they would spontaneously occur. • Structural materials, including keratin (the protein found in hair and nails) and collagen (the protein found in connective tissue).

• Specific binding, such as antibodies that bind specifically to foreign substances to identify them to the body's immune system. • Specific carriers, including membrane transport proteins that move substances across cell membranes, and blood proteins, such as hemoglobin, that carry oxygen, iron, and other substances through the body.

• Contraction, such as actin and myosin fibers that interact in muscle tissue.

• Signaling, including hormones such as insulin that regulate sugar levels in blood.

2. Structure of Amino Acid Monomers • Consist of an asymmetric carbon covalently bonded to: • Hydrogen • Amino group • Carboxyl (acid) group • Variable R group specific to each amino acid

Properties of Amino Acids •

Grouped by polarity

• Variable R groups (side chains) confer different properties to each amino acid: • polar, water soluble. • non-polar, water insoluble • positively charged • negatively charged.

4 levels of protein structure: • primary • secondary • tertiary •quaternary

3. Primary Structure

• Unique sequence of amino acids in a protein • Slight change in primary structure can alter function • Determined by genes • 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

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 can self replicate makes up genes which code for proteins is passed from one generation to another – RNA: single stranded 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 DNA Ribose 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)

DNA: • Double helix • 2 polynucleotide chains wound into the double helix • Base pairing between chains with H bonds • A - T • C - G

Summary of the Organic Molecules: