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MOLECULES OF LIFE
CH5
• All living things are made up of 4 classes of
large biomolecules:
o Proteins
o Carbohydrates
o Lipids
o Nucleic acids
• Molecular structure and biological function
are intricately related
I. Macromolecules
• Large molecules made of thousands of
atoms covalently bonded
• 3 of the 4 biomolecules are polymers:
proteins, carbs, nucleic acids
• Polymer: a macromolecules made of
repeating units called monomers
The Synthesis and Breakdown of
Macromolecules
• Macromolecules are
made by dehydration
reactions
• Macromolecules are
broken down by
hydrolysis reactions
II. Carbohydrates
• Sugars and the polymers of sugars
o Monosaccharides
o Disaccharides
o polysaccharides
A. Monosaccharides (CH2O)
• structure
o A single sugar ex: glucose
o Classified by number of carbons in
chain and location of carbonyl
• Most monosaccharides exist as a ring
• isomers
o Molecules with same structural formula
but different arrangement of atoms
o Ex: glucose, fructose, and galactose
• function
oQuick energy source
oImmediately enters into cellular
respiration for production of ATP
B. Disaccharides
• Structure
o2 monosaccharides linked via
dehydration reactions
oEX: sucrose, lactose
• Function
Energy
C. Polysaccharides
• Long chain of GLUCOSE molecules linked
via dehydration reactions
• 2 groups of polysaccharides
o Storage: starch and glycogen
o Structural: cellulose chitin
1. Storage polysaccharides
• Glycogen
– Stores glucose in animals
– Many glucose molecules linked via α1-4
linkages
• Starch
– Stores glucose in plants
– Many glucoses linked by α1-4 linkages
– http://bcs.whfreeman.com/thelifewire/conte
nt/chp03/0302002.html
2.
structural polysaccharides
• cellulose
o forms cell wall in plants
o many glucoses linked via β1-4 linkages
• chitin
o forms exoskeleton in arthropods and cell
wall in fungi
• Most animals have enzymes to break α1-4
linkage but not β1-4 linkage.
• Most cellulose consumed exits as insoluble
fiber
• Only some bacteria have enzymes to break
β1-4 linkage
III. Lipids
• Diverse group of hydrophobic molecules
• Only macromolecule that doesn’t form
polymer
A. Triglycerides (fats and oils)
• One glycerol + 3 fatty
acids linked via
dehydration reactions
http://www2.nl.edu/jste/bioch
em.htm
Fatty Acid
• Long chain of C and H with a carboxyl
group
• Usually 14 to 20 Cs
• Fatty acids can be
– Saturated: no carbon to carbon double
bonds. Solid at room temp
– Monounsaturated: 1 carbon to carbon
double bond. Liquid at room temp
– Polyunsaturated: more than 1 carbon to
carbon double bond. Liquid at room temp
– Function
• Long term energy storage
• Seeds use stored triglycerides as energy
during germination
• Insulation in mammals
• http://bcs.whfreeman.com/thelifewire/
content/chp03/0302002.html
B. Phospholipids
• Structure
o One glycerol + 2 fatty acids + 1 phosphate
head
• Property
o Amphiphathic: polar charged phosphate
head and nonpolar uncharged fatty acid
tails
• Function:
o Make up phospholipid bilayer found in
all biological membranes
C. Waxes and Steroids
• Waxes
– Function as protective barrier
• Steroids
– Function as chemical messengers
IV. Proteins
• About 50% of all macromolecules are
proteins
A. Functions of Proteins
• Polypeptide: long chain of amino acids
• Protein: biologically functional molecule
made of 1 or more polypeptides
B. Amino Acids: monomer of proteins
• general structure
o all contain amino and
carboxyl group but
differ in their R group
Groups of amino acids: based on the
characteristics of R group
Linking of amino acids
• Link to form peptide bond
• Each polypeptide has a unique order of
amino acids
http://www2.nl.edu/jste/biochem.htm
http://bcs.whfreeman.com/thelifewire/conte
nt/chp03/0302002.html
Protein Structure
• Protein structure is determined by the
sequence of amino acids
• Structure determines its function
• As protein is being synthesized, it begins to
fold into its correct shape
• Proteins fold as a result of the interactions
between amino acids in the polypeptide
chain
• http://www.ncbi.nlm.nih.gov/sites/entrez?db
=structure
There are 4 levels of protein structure
• primary structure
• number and order of amino acids
in the protein chain
• primary structure is determined
by______________
• all proteins have a different
primary structure
• secondary structure
– Hydrogen bonding between amino and
carboxyl groups
– 2 forms: α helix and β sheet
• Tertiary structure
– Interaction among the R groups of amino
acids
– Interactions include ionic bonds,
hydrogen bonds, hydrophobic
interactions, and covalent bonds
– What type of amino acids involved in
each?
• Quaternary structure
• 2 or more
polypeptide chains
associated together
to form a functional
protein
• In a cell, special proteins called chaperonins
help proteins fold into their shape
• http://parasolwww.cs.tamu.edu/groups/amatogroup/resea
rch/folding/proteinA.php
•
• What would happen if the primary
structure of a protein was changed?
D. Protein unfolding
• Denaturation: unfolding of a protein as a
result of changes in pH and temp
V. Nucleic Acids
• The information
molecules: contain
the code to make
proteins
• Structure
– Long chains of nucleotides Nucleotides
– Made of a:
• 5 carbon sugar
• Phosphate group
• One of 4 bases
• Function
– DNA: stores hereditary
info
– RNA: expresses it