CHAPTER 5 The Structure and Function of Macromolecules “You are what you eat!”

What does it mean to be a MACROmolecule?  You must be a Large molecule  You have a complex structure “little” molecule Macromolecule

I. Most macromolecules are polymers, built from monomers  What is a polymer? Poly = many; mer = part. A long molecule made of monomers bonded together  What is a monomer? A monomer is a sub-unit of a polymer.

 Three of the classes of life’s organic molecules are polymers (made up of monomers) Carbohydrates, Proteins, Nucleic acids

A. Making and Breaking Polymers  How do monomers bind to form polymers? condensation reactions called dehydration synthesis (removal of water)

How can polymers break down when monomers are needed?  Hydrolysis reaction Hydro = water; lysis = break Water is added and the lysis of the polymer occurs.

Hydrolysis

II. Classes of Organic Molecules: Carbohydrates Lipids Proteins Nucleic Acids

1. CARBOHYDRATES

 What are Carbohydrates? Sugars and their polymers Carbo = carbon, hydrate = water; carbohydrates have the molecular formula (CH 2 O) n  Functions of Carbohydrates in living things: Major fuel/energy source Can be used as raw materials for other Macromolecules Complex sugars = building material in plants  What is the Carbohydrate Monomer? Monosaccharide (“mono” = one; “saccharide” = sugar)

1. Structure of Monosaccharides  Contain only C, H, O  Hydroxyl group is attached to each carbon  One carbon contains a carbonyl group

Classified according to the size of their carbon chains and location of Carbonyl group

 In aqueous solutions many monosaccharides form rings:

2. Structure of Disaccharides  Consist of two monosaccharides  Are joined by a glycosidic linkage  What reaction forms the glycosidic linkage? Dehydration synthesis

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 form of energy, easily hydrolyzed to glucose units

 Cellulose is a fiber-like structural material made of glucose monomers used in plant cell walls

Why is Cellulose so strong?  Glucose monomers are flipped to expose equal Hydroxyl groups on either side of the chain  When Cellulose chains are lined up next to each other, they Hydrogen Bond making a strong material that’s difficult to break!

 Glycogen is the animal short-term storage form of energy  Glucose monomers

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

2. LIPIDS  What are Lipids? Fats, phospholipids, steroids, waxes, pigments Hydrophobic (“hydro”=water; “phobic” = fearing) Consist mostly of hydrocarbons Do NOT consist of monomers and polymers

 Functions of Lipids in living things: Energy storage membrane structure Protects against desiccation (drying out) Insulates against cold. Absorbing shock

1. Structure of Lipids  Consist of a single glycerol and usually 1-3 fatty acid hydrocarbon chains  Glycerol – an alcohol with three carbons  Fatty Acid - Long Hydrocarbon chains with a Carboxyl group at one end.

Saturated and Unsaturated Fats  Unsaturated fats : one or more double bonds between carbons in the fatty acids allows for “kinks” in the tails liquid at room temp most plant fats  Saturated fats: No double bonds in fatty acid tails solid at room temp most animal fats (a) Saturated fat and fatty acid Stearic acid (b) Unsaturated fat and fatty acid cis double bond causes bending Oleic acid

Saturated fatty acid

A. Phospholipids  Structure: Glycerol + 2 fatty acids + phosphate group.  Function: Main structural component of membranes, where they arrange in bilayers.

Phospholipids in Water

B. Triglycerides  Structure - Have one glycerol and three fatty acid chains  Function - necessary for certain bodily functions (fat stores), but high levels of them can lead to heart disease.

This is a triglyceride:

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

D. Steroids  Structure: Four carbon rings with no fatty acid tails  Functions: Component of animal cell membranes (Ex: Cholesterol) Modified to form sex hormones

PROTEINS

3. Proteins  What are Proteins? Chains of amino acid monomers connected by peptide bonds Have a 3 dimensional globular shape

Examples of Protein Functions  Enzymes (see next slide for a visual) Act as catalysts to speed up the rate of reactions  Immune System Binding of antibodies (proteins) to foreign substances in the body  Transport Transport proteins move substances across cell membranes Hemoglobin carries oxygen, iron, and other substances through the body  Muscle Contraction actin and myosin protein fibers interact in muscle tissue  Cell Signaling Hormones such as insulin regulate sugar levels in blood

Enzymes  Are a type of protein that acts as a catalyst, speeding up chemical reactions up to 10 billion times faster than they would spontaneously occur.

Amino Acids  Are the monomers of polypeptides Structure: amino groups, carboxyl groups, and Differing side chains, called R groups, effects the properties of amino acids.

20 different amino acids The sequence of amino acids and the interactions of the different amino acids determine a proteins shape

 Peptide bonds connect amino acids to form polypeptide chains  One or more polypeptide chains make up a protein

Proteins are very complex! Their specific structure determines their function. HEMOGLOBIN: Transport of gases and iron in blood ACTIN: Filament involved in muscle contraction

Four Levels of Protein Structure  Primary structure Is the unique sequence of amino acids in a polypeptide Figure 5.20 – Amino acid subunits + H 3 N Amino end o Carboxyl end o c Gly ProThr Gly Thr Gly Glu Seu Lys Cys Pro Leu Met Val Lys Val Leu Asp Ala Val Arg Gly Ser Pro Ala Gly lle Ser Pro Phe His Glu His Ala Glu Val Phe Thr Ala Asn Asp Ser Gly Pro Arg Tyr Thr lle Ala Leu Ser Pro Tyr Ser Tyr Ser Thr Ala Val Thr Asn Pro Lys Glu Thr Lys Ser Tyr Trp Lys Ala Leu Glu Lle Asp

OC  helix  pleated sheet Amino acid subunits N C H C O C N H C O H R C N H C O H C R N H H R C O R C H N H C O H N C O R C H N H H C R C O C O C N H H R C C O N H H C R C O N H R C H C O N H H C R C O N H R C H C O N H H C R C O N H H C R N H O O C N C R C H O C H R N H O C R C H N H O C H C R N H C C N R H O C H C R N H O C R C H H C R N H C O C N H R C H C O N H C  Secondary structure Is the folding or coiling of the polypeptide into a repeating configuration resulting from hydrogen bonding of amino with carboxyl groups Includes the  helix and the  pleated sheet H H Figure 5.20

 Tertiary structure Is the overall three-dimensional shape of a polypeptide Results from interactions between amino acids and R groups CH 2 CH OHOH O C HO CH 2 NH 3 + C -O-O CH 2 O SS CH CH 3 H3CH3C H3CH3C Hydrophobic interactions and van der Waals interactions Polypeptide backbone Hydrogen bond Ionic bond CH 2 Disulfide bridge

 Quaternary structure Is the overall protein structure that results from the aggregation of two or more polypeptide subunits

 Chaperonins Are protein molecules that assist in the proper folding of other proteins Hollow cylinder Cap Chaperonin (fully assembled) Steps of Chaperonin Action: An unfolded poly- peptide enters the cylinder from one end. The cap attaches, causing the cylinder to change shape in such a way that it creates a hydrophilic environment for the folding of the polypeptide. The cap comes off, and the properly folded protein is released. Correctly folded protein Polypeptide Figure 5.23

Sickle Cell Disease: A simple change in Primary Structure

Factors That Affect Protein Shape  Proteins can denature (fall apart) if: pH is too high or too low Temperature is too high Salinity is too high  Denatured proteins are biologically inactive

NUCLEIC ACIDS

4. Nucleic Acids : The stuff of Genes  Nucleic acids store and transmit hereditary information  Genes Are the units of inheritance Program the amino acid sequence of polypeptides Are made of nucleic acids

Two Kinds of Nucleic Acids  DNA ( Deoxyribonucleic acid) double stranded can self replicate makes up genes which code for proteins is passed from one generation to another  RNA ( Ribonucleic acid) single stranded functions in actual synthesis of proteins coded for by DNA is made from DNA

1. Monomers of Nucleic Acids  Both DNA and RNA are composed of nucleotide monomers.  Nucleotides are composed of: a 5 carbon sugar, a phosphate group, and a nitrogenous base Phosphate 5 Carbon Sugar Nitrogenous Base

2. Building the Polymer  On your paper, label the phosphate groups and 5 carbon sugars. List the 4 different kinds of nitrogenous bases, too.

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:

Saturated fatty acid Unsaturated fatty acid Why are Unsaturated Fats better for you than Saturated Fats?