Biological Molecules
Biological Molecules
• Life is carbon-based chemistry
• Hydrolysis and Synthesis of Biological
Molecules
• Carbohydrates
• Lipids
• Proteins
• Nucleic Acids
Life is carbon-based chemistry
• Organic is used to describe molecules that
have a carbon skeleton and some
additional hydrogen atoms
• Life is composed of organic molecules
• Inorganic molecules include carbon
dioxide, water and all other non-carbon
molecules
Life is carbon-based chemistry
• The tremendous diversity of organic molecules
is due to the diverse functional groups that
attach themselves to common carbon skeletons:
• Hydrogen (-H)
• Hydroxyl (-OH)
• Carboxyl (-COOH)
• Amino (-NH2)
• Phosphate (-H2PO4)
• Methyl (-CH3)
Hydrolysis and Synthesis of
Biological Molecules
• Small organic molecules are used as
subunits to synthesize longer molecules
• The individual subunits are called
monomers
• The longer molecules are called polymers
Hydrolysis and Synthesis of
Biological Molecules
• Monomers are linked to monomers in a chemical
process called dehydration synthesis
• The –H group is removed from one monomer
and the –OH group is removed from the second
monomer
• The two monomers join by forming a covalent
bond
• The –H group and –OH group bond to form a
water molecule
Hydrolysis and Synthesis of
Biological Molecules
• Polymers are disassembled into
monomers through a process called
hydrolysis
• The polymer splits into monomers
• A water molecule splits and releases a –H
group and a –OH group
• The –H group and –OH group bond to the
monomers to complete their structure
Carbohydrates
• Contain carbon, hydrogen and oxygen in
the constant ratio of 1:2:1
• Carbohydrates are “hydrates of carbon”
• C1H201 or CH20
• All carbohydrates are either small, simple
sugars or polymers of these simple sugars
Carbohydrates
Monosaccharides One sugar
molecule
Disaccharides
Two sugar
molecules
Polysaccharides
Many sugar
molecules
Glucose
Fructose
Galactose
Sucrose
Lactose
Maltose
Starch
Glycogen
Cellulose
Lipids
• Lipids contain large regions of H and C
atoms joined by non-polar covalent bonds
• Non-polar regions are hydrophobic
• Lipids are not soluble in water
• Three major groups of lipids
• (1) oils, fats and waxes
• (2) phospholipids
• (3) steroids
Oils, Fat and Waxes
• Contain only C, H and O atoms
• Composed of one or more fatty acids
subunits attached to a glycerol subunit
• Are straight chains: do not have ring
structures
• Function as source of energy
Oils, Fat and Waxes
• Fatty acid chains that have no C=C double
bonds are said to be saturated with H
atoms
• Fatty acid chains that have C=C double
bonds are said to be unsaturated with H
atoms
• Saturated fatty acid chains are straight
• Unsaturated fatty acid chains are kinked
Oils, Fat and Waxes
• Oils are liquid at room temperature
because they are unsaturated → kinks
• Waxes are solid at room temperature
because they are saturated → straight
Phospholipids
• Similar to structure of fats, waxes and oils
except one of the three fatty acid chains is
replaced by a phosphate group containing
a polar functional group
• The two fatty acid chains are hydrophobic
• The phosphate head (being polar) is
hydrophilic
• Function as basic component of
membranes
Steroids
• Composed of four rings of carbon fused
with various functional groups
• Steroids are synthesized from cholesterol
• Function as hormones and components of
animal cell membranes
Proteins
• Proteins are polymers of amino acid subunits
• The bond between amino acid subunits is called
a peptide bond (formed by dehydration
synthesis)
• Diversity of proteins is due to diversity of amino
acids and the diverse ways amino acids arrange
themselves
• Proteins function as enzymes, structural
components, transport proteins, energy storage,
cross-membrane transport, and hormones
Proteins
• Amino acids are composed of a central C
atom bonded to four different functional
groups:
• (1) amino group (-NH2)
• (2) carboxylic acid group (-COOH)
• (3) hydrogen group (-H)
• (4) variable group (-R)
Proteins
• The –R group creates the diversity of
amino acids
• Some -R groups are small, others large
• Some –R groups are hydrophobic, others
hydrophilic
• The type of –R group directly affects the
structure of the protein
Proteins
• Proteins have four levels of structure
• (1) Primary Structure: sequence of amino
acids in the linear protein polymer
• (2) Secondary Structure: simple repeating
pattern created by hydrogen bonding
between amino acid subunits
• Secondary structure can be either a helix
or pleated sheet
Proteins
• (3) Tertiary Structure: complex 3
dimensional shape formed by folding over
of secondary structure
• Tertiary structure is due to disulfide
bridging between neighbouring cysteine
amino acids; size of –R group;
hydrophobic/hydrophilic interactions
Proteins
• (4) Quaternary Structure: due to joining
together of smaller proteins in order to
form a larger protein complex
Nucleic Acids
• Nucleic acids are polymers of nucleotide
subunits
• Nucleotides are composed of three
components themselves:
• (1) a five C sugar (ribose/deoxyribose)
• (2) a phosphate group
• (3) a N containing base
Nucleic Acids
• It is the diversity in N containing bases that
creates diversity in nucleotides
• It is the diversity in sugars that adds to the
diversity of nucleic acids
Nucleotides
DNA
(deoxyribose
sugar)
Adenine
RNA
(ribose sugar)
Thymine
Uracil
Guanine
Guanine
Cytosine
Cytosine
Adenine
Nucleic Acids
• Nucleic acids function primarily as the
molecules of heredity and the blueprint for
protein synthesis (DNA and RNA)
• Nucleic acids also act as intracellular
messengers (cAMP), coenzymes and
energy carrier molecules (ATP)