Chapter 5
The Structure and Function of
Large Biological Molecules
Focus on:
Elements in each large biological
molecule.
How these molecules are linked and
unlinked.
Examples and functions of each type of
molecule.
Macromolecules
Large molecules formed by joining many
subunits together.
Also known as “polymers”.
Monomer
A building block of a polymer.
AP Bi
ology
Condensation Synthesis or
Dehydration Synthesis
The chemical reaction that joins
monomers into polymers.
Covalent bonds are formed by the
removal of a water molecule between the
monomers.
Hydrolysis
Reverse of condensation synthesis.
Hydro- water
Lysis - to split
Breaks polymers into monomers by
adding water.
Four Main Types of Macromolecules
or Large Biological Molecules
Carbohydrates
Lipids
Protein
Nucleic acids
For each Macromolecule know the
following:
Elements it contains
Monomer units and structures
Examples
Uses or roles
Carbohydrates
Used for fuel, building materials, and
receptors.
Made of C,H,O
General formula is CH2O
C:O ratio is 1:1
Types Of Carbohydrates
Monosaccharides
Disaccharides
Oligosaccharides
Polysaccharides
Monosaccharides
Mono - single
Saccharide - sugar
Simple sugars.
3 to 7 carbons.
Can be in linear or ring forms.
Monosaccharides
Can be “Aldoses” or “Ketoses” depending
on the location of the carbonyl group.
Examples
Glucose
Galactose
Ribose
Fructose
- OSE
Word ending common for many
carbohydrates.
Disaccharides
Sugar formed by joining two
monosaccharides through a “glycosidic
linkage”.
Examples
Maltose = glucose + glucose
Lactose = glucose + galactose
Sucrose = glucose + fructose
Oligosaccharides
2 - 10 joined simple sugars.
Used in cell membranes.
Polysaccharides
Many joined simple sugars.
Used for storage or structure.
Examples:
◦ Starch
◦ Cellulose
◦ Glycogen
α glucose and β glucose
Starch
Made of 1-4 linkages of α glucose.
Linkage makes the molecule form a helix.
Fuel storage in plants.
α glucose
Cellulose
Made of 1-4 linkages of β glucose.
Linkage makes the molecule form a
straight line.
Used for structure in plant cell walls.
β glucose
Comment
Most organisms can digest starch (1- 4 α
linkage), but very few can digest cellulose
(1- 4 β linkage).
Another example of the link between
structure and function.
Glycogen
“Animal starch”
Similar to starch, but has more 1-6
linkages or branches.
Found in the liver and muscle cells.
Starch
Glycogen
Lipids
Diverse hydrophobic molecules
Made of C,H,O
No general formula
C:O ratio is very high in C
Not strictly speaking a macromolecule like
the others
Fats and Oils
Fats - solid at room
temperature.
Oils - liquid at room
temperature.
Fats and Oils
Made of two kinds of smaller molecules.
◦ Fatty Acids
◦ Glycerol
Fatty Acids
A long carbon chain (12-18 C) with a COOH (acid) on one end and a -CH3
(fat) at the other.
Acid
Fat
Neutral Fats or Triacylglycerols
Three fatty acids joined to one glycerol.
Joined by an “ester” linkage between the
-COOH of the fatty acid and the -OH of
the alcohol.
Saturated Fats
Unsaturated Fats
Saturated - no double bonds.
Unsaturated - one or more C=C bonds.
Can accept more Hydrogens.
Double bonds cause “kinks” in the
molecule’s shape.
Question
Why
do fats usually contain
saturated fatty acids and oils usually
contain unsaturated fatty acids?
The double bonds push the
molecules apart, lowering the
density, which lowers the melting
point.
Fats
Differ in which fatty acids are used.
Used for energy storage, cushions for
organs, insulation.
Question ?
Which has more energy, a kg of fat or a
kg of starch?
Fat - there are more C-H bonds which
provide more energy per mass.
Phospholipids
Similar to fats, but have only two fatty
acids.
The third -OH of glycerol is joined to a
phosphate containing molecule.
Result
Phospholipids have a hydrophobic tail, but
a hydrophilic head.
Self-assembles into micelles or bilayers,
an important part of cell membranes.
Steroids
Lipids with four fused rings.
Differ in the functional groups attached to
the rings.
Examples:
◦ cholesterol
◦ sex hormones
Proteins
The molecular tools of the cell.
Made of C,H,O,N, and sometimes S.
No general formula.
Uses Of Proteins
Structure
Enzymes
Antibodies
Transport
Movement
Receptors
Hormones
Proteins
Polypeptide chains of Amino Acids linked
by peptide bonds.
Amino Acids
All have a Carbon with four attachments:
-COOH (acid)
-NH2 (amine)
-H
-R (some other side group)
R groups
20 different kinds:
◦ Nonpolar - 9 AA
◦ Polar - 6 AA
◦ Electrically Charged
Acidic - 2 AA
Basic - 3 AA
Amino Acids
Amino Acids
R groups
Contain the S when present in a protein.
◦ Cysteine or Cys
◦ Methionine or Met
The properties of the R groups
determine the properties of the protein.
Polypeptide Chains
Formed by dehydration synthesis
between the carboxyl group of one AA
and the amino group of the second AA.
Produce an backbone of: (N-C-C)X
Levels Of Protein Structure
Organizing the polypeptide into its 3-D
functional shape.
◦
◦
◦
◦
Primary
Secondary
Tertiary
Quaternary
Primary
Sequence of amino
acids in the
polypeptide chain.
Many different sequences are
possible with 20 AAs.
Secondary
3-D
structure formed by hydrogen
bonding between parts of the peptide
backbone.
Two main secondary structures:
◦ α helix
◦ pleated sheets
Tertiary
Bonding between the R groups.
Examples:
◦ hydrophobic
◦ ionic bonding
◦ Disulfide bridges
interactions
(covalent bond)
Quaternary
When two or more polypeptides unite to
form a functional protein.
Example: hemoglobin
Is Protein Structure Important?
Denaturing Of A Protein
Events
that cause a protein to lose
structure (and function).
Example:
◦ pH shifts
◦ high salt concentrations
◦ heat
Chaperone Proteins
Large protein complexes that help fold
other proteins into their correct shape.
Often used when cells are stressed to
keep proteins intact and functioning.
Comment
Many other amino acids are possible
(change the R group)
Whole new group of proteins with new
properties can be made
Genetic engineering can use bacteria to
make these new proteins
Nucleic Acids
Informational polymers
Made of C,H,O,N and P
No general formula
Examples: DNA and RNA
Nucleic Acids
Polymers of nucleotides
Nucleotides have three parts:
◦ nitrogenous base
◦ pentose sugar
◦ phosphate
Nitrogenous Bases
Rings of C and N
The N atoms tend to take up H+ (base).
Two types:
◦ Pyrimidines (single ring)
◦ Purines (double rings)
Pentose Sugar
5-C sugar
Ribose - RNA
Deoxyribose – DNA
RNA and DNA differ in a –OH group on
the 2nd carbon.
Nucleosides and Nucleotides
Nucleoside = base + sugar
Nucleotide = has the trio of base + sugar + Pi
DNA
Deoxyribonucleic Acid.
Makes up genes.
Genetic information
for life.
RNA
Ribonucleic Acid.
Structure and protein synthesis.
Genetic information for a few viruses
only.
Control mechanisms for genes.
DNA and RNA
More will be said about DNA and RNA in
future lessons.
Summary
Role
of hydrolysis and dehydration
synthesis
For each macromolecule, know the
following:
◦ Elements and monomers
◦ Structures
◦ Functions
◦ Examples