INTRODUCTION TO MACROMOLECULES
BUILDING BLOCKS
Overview
Macromolecules form when smaller molecules (building blocks or subunits) come together
Monomers are joined by covalent bonds to form polymers
Building blocks of proteins
Amino acids
20 common amino acids
Central carbon with attached hydrogen, amino group, carboxylic acid group, and a R group
Building blocks of lipids
Fatty acids
Long hydrophobic hydrocarbons
Glycerol
A triose
Building blocks of nucleic acids
Nucleotides
Nitrogenous base
A, T, C, U, and G
Pentose sugar
Ribose in RNA
Deoxyribose in DNA
Phosphate
Building blocks of polysaccharides
Monosaccharides
(CH
2
O)
n
SYNTHESIS AND DEGRADATION
Dehydration synthesis
Monomers are joined to form polymers by the removal or a water molecule (dehydration)
This results in covalent attachment of the subunits
The bond forms when a hydrogen from one monomer is linked to a hydroxyl group from another monomer
Hydrolysis
Macromolecules can be broken down into their subunits by adding a water molecule across bonds
PROTEINS
Functions
Structural
Enzymatic
Catalyze chemical reactions
Structure
Proteins are polymers of amino acids
There are 20 common amino
Each has a central carbon attached to 4 groups
Hydrogen
Amine
Carboxylic acid
An R group
Amino acids differ by their R groups
There are 20 different R groupss.
2 amino acids are connected by dehydration synthesis
The covalent bond is called a peptide bond
Levels of organization
Primary structure
Sequence of amino acids.
The 20 different amino acids can be joined in any sequence
This sequence is determined by the DNA sequence of the gene that encodes for that particular protein
Secondary structure
Do to interactions of the amino acids near each other
Hydrogen bonds between amino hydrogens and carboxyl oxygens
Results in an
a
-helix configuration or a
b
- sheet configuration
Tertiary structure
The 3-dimensional folding of the polypeptide chain
Do to interaction of R-groups of amino acids some distance away from each other
These interactions could be hydrogen bonding, ionic bonding, or covalent bonding.
Quaternary structure
Interaction between proteins
Denaturation
Most secondary, tertiary, and quaternary structure bonds are weak
The primary structure, formed by covalent bonds, is very stable
The amino acid chain can easily be unfolded (denatured) by changes in pH and temperature
When a protein loses its structure, it can no longer perform its function
POLYSACCHARIDES
Functions
Energy reserve
Glycogen in animals
Starch in plants
Structure
Cellulose in the cell walls of plants and some algae
Structure
Monomer
Monosaccharides
Carbon, hydrogen, and oxygen in a 1:2:1 (CH2O)n.
Monosaccharides contain from 3 to 7 carbons
Trioses contain 3 carbons
Example: glycerol
Tetroses contain 4 carbons
Pentoses contain 5 carbons
Example: ribose
Hexoses contain 6 carbons
Example: glucose
Heptoses contain 7 carbons
Larger carbohydrates are created by joining together monosaccharides by dehydration synthesis reactions
Disaccharides
2 monosaccharides are joined
Polysaccharides
Polymer of many monosaccharides
LIPIDS
Function
Long term storage of energy
Also insulates and cushions major organs
Component of membranes
Types
Fats (lard and butter) are solids at room temperature
Oils (vegetable oils) are liquids at room temperature
Structure
Lipids are composed of glycerol and three fatty acids
Two to three fatty acids are bonded to the glycerol by dehydration synthesis
Fatty acids can be removed from the glycerol by hydrolysis
Fatty acids
Hydrocarbon chains with a carboxyl group
Most have 16 - 18 carbons
Saturated fatty acids
No double bonds between the carbon atoms
The carbons are saturated with hydrogens
These will result in lipids that are less fluid
Unsaturated fatty acids
One or more (polyunsaturated) double bonds between the carbon atoms
These will result in lipids that are more fluid
Fatty acids are non-polar and therefore hydrophobic
Phospholipids
Lipids with two fatty acids and a phosphate group attached to glycerol
Amphipathic
Has a hydrophilic head and hydrophobic tail
Lipid bilayer
Two layers of phospholipids
Heads face out into the water
Tails face towards each
NUCLEIC ACIDS
Function
Store genetic information
Transfer genetic information during reproduction
Controls protein synthesis
Types
DNA compromises the chromosomes
RNA is used in protein synthesis
Monomers
Nucleic acids are polymers of nucleotides
Nucleotides are bonded by dehydration synthesis
Nucleotide consists of three parts
Sugar
A pentose
Ribose in RNA
Deoxyribose in DNA
Phosphate group
Base
A, T, C, and G in DNA
A, U, C, and G in RNA
The order of these bases controls the amino acid sequence in proteins
Structure
Backbone
Alternating sugars and phosphate
Bases
Stick out from the sugars
DNA is often double stranded, while RNA can be single stranded, double stranded, or both