Download The Structure and Function of Large Biological Molecules

The Structure and Function
of Large Biological
Molecules
Introduction to Macromolecules
Biological Molecules
• One of the most important
understandings in nature is that
the same elements are used
multiple times in various ways to
get the diversity that is seen.
• Noticing patterns in molecules can
help you to understand form and
function of a molecule
Functional Groups
• At times, a chemical
group may replace one or
more of the hydrogens
bonded to the carbon
skeleton.
• These groups may
participate in reactions
and may play a role in the
function of the molecule
because of shape
Functional Groups
1)Hydroxyl
– Hydrophilic; increases solubility
Functional Groups
2) Carbonyl
– Hydrophilic; increases solubility
– Know the difference between a ketone and an
aldehyde
Functional Groups
3) Carboxyl
– Hydrophilic; increases solubility
Functional Groups
4) Amino
– Hydrophilic;
increases
solubility
Functional Groups
5) Sulfhydryl
– Hydrophilic;
increases
solubility
Functional Groups
6) Phosphate
– Hydrophilic;
increases
solubility
Functional Groups
7) Methyl
– Non-Reactive
– Acts as a recognizable tag on biological molecules
Macromolecules
• Macromolecules (or polymers)
are long, chain-like molecules
– Consists of many similar or identical
building blocks (monomers) linked
by covalent bonds
• Includes carbohydrates, nucleic
acids, and proteins
– Lipids are not a true macromolecule
• Built via condensation or
dehydration reaction (or
dehydration synthesis)
– Take away water molecule
– Helped by enzymes to speed
reaction
• Breakdown via hydrolysis
– Add water molecule
– Occurs in digestion
Carbohydrates
• Monomers: monosaccharides
or simple sugars
– Simplified formula is CH2O
– Structure is used to classify sugars
• General structure includes a
carbonyl group and multiple
hydroxyl groups
– Location of carbonyl will
determine if it is aldose or ketose
(aldehyde or ketone sugars)
• Sugars are made up of 3-7
carbons in skeleton which may be
linear or ringed
• Spatial arrangement around
asymmetric carbons is important
– Examples: glucose, fructose,
galactose
– Important in cellular respiration
and synthesis of materials
Carbohydrates
• Disaccharides: 2 sugars joined by a
covalent bond
– The covalent bond is known as a glycosidic
linkage when it is between 2 monosaccharides
– The bond is formed by dehydration reaction
– Examples: Maltose, sucrose, lactose
Carbohydrates
• Polymers: polysaccharides;
these are macromolecules
also formed via glycosidic
linkages
– Storage polysaccharides
• Starch – polymer of glucose
monomers found in plants;
starch allows plants to
stockpile glucose
– α configuration of glucose
– Humans consume these in
potatoes and grains
• Glycogen – a branched
polymer of glucose found in
most vertebrates; largely
stored in liver and muscle cells
and is released when the body
needs sugar
Carbohydrates
– Structural Polysaccharides
• Cellulose – major
component in cell walls
– β configuration of glucose
(every other glucose
monomer is upside down)
– Important in digestion –
humans do not have the
appropriate enzymes to
digest β linkages, but
promotes healthy digestion
– Most abundant organic
compound on Earth
• Chitin – used by arthropods
in exoskeletons
– Similar structure to
cellulose, but contains
nitrogen
Lipids
• Lipids do not include true
polymers and are not generally
considered macromolecules
• They are grouped together
because they are hydrophobic
• Largely composed of
hydrocarbons
• Includes: fats, phospholipids,
steroids, waxes and pigments
Lipids
• Fats (triacylglycerol or
triglyceride) – composed of
glycerol attached to 3 fatty
acids bonded via an ester
linkage
– Ester linkage occurs between
hydroxyl and carboxyl groups
– Glycerol – alcohol with 3
carbons each with its own
hydroxyl group
– Fatty acid – long carbon
skeleton (16-18 common) with
one carbon end associated
with a carboxyl group. The
rest is a long hydrocarbon
chain.
• Important in energy storage
and protection
• Fats
Lipids
– Saturated fat or fatty acid
• No double bonds which allows the
greatest number of hydrogens to
be attached to the carbon skeleton
• Includes most animal fats
• Solid at room temp
– Unsaturated fat or fatty acid
• Has 1 or more double bonds and
thus fewer hydrogen atoms
• A kink in the chain will occur
whenever a cis double bond occurs
(as opposed to trans double bonds
– ie trans fats found in
hydrogenated veg. oil)
• Includes plant and fish oils
• Liquid at room temp
Lipids
• Phospholipids –
essential for cell
membrane composition
– Similar to fat molecule,
but only have 2 fatty
acids attached to
glycerol
• The 3rd hydroxyl group is
attached to a phosphate
group (these can in turn
bond to other molecules)
• Hydrocarbon tail is
hydrophobic (inside the
bilayer), phosphate group
is hydrophilic (face
outward)
Lipids
• Steroids – carbon
skeleton composed of
4 fused rings with
different chemical
groups attached
– Includes many
hormones and
cholesterol
– Fat can affect
cholesterol levels
Proteins
• Proteins account for ~50% of cell’s dry
mass and extremely important in
functions
Proteins
• Monomers are amino acids
– 20 different amino acids that are
composed of an asymmetric carbon
surrounded by an amino group,
carboxyl group, hydrogen and an R
group or side chain which varies
• Polymers are polypeptides
– Different combinations of A.A. allows
for the variety of proteins
– A.A. are attached with a covalent bond
between the carboxyl group of one to
the amino group of another called a
peptide bond
Proteins
• Protein structure and function
are intimately linked
• The specific folds of a protein
are determined by the ordering
of A.A. in the polypeptide chain.
This folding in turn determines
shape.
• Shape will then determine
function.
Proteins
• Primary Structure – the
unique sequence of
amino acids
• Secondary Structure –
coils and folds in the
polypeptide chain caused
by hydrogen bonds
between repeating
constituents
– α helix – a coil held
together by hydrogen
bonds at every 4th A.A.
– β pleated sheet – folding
creating pleats at particular
intervals
Proteins
• Tertiary Structure – Overall shape
of a polypeptide do to interactions
of R groups
– Shape may be reinforced by disulfide
bridges
• Covalent bond between sulfhydryl
groups
• Quaternary Structure – overall
protein structure (potentially
several polypeptide chains
interacting)
Proteins
• Changes in primary
structure lead to changes
in further structures,
potentially leads to a
misfunctioning or
nonfunctioning protein
– Example: Sickle Cell
• Protein shape and
function can also be
changed via denaturation
– pH, temperature, salt
concentration, etc.
Proteins
• Chaperonins or chaperone structure
are specialized proteins that assist in
the proper folding of proteins
– Are not specific, but keep the protein
away from potentially bad influences
– Folding is spontaneous
Nucleic Acids
• Main function is to store
and transmit genetic
information
• 2 kinds: RNA and DNA
– These are both
polymers/macromolecules
– The monomers are
nucleotides
• Composed of a nitrogenous
base, a 5-carbon sugar, and a
phosphate group
– Nucleosides are this unit minus
the phosphate group
Nucleic Acids
• Two groups of
nitrogenous bases
– Pyrimidines: single 6-C ring
• Cytosine, thymine, uracil
– Purines: double fused rings
(1 5-C, 1 6-C)
• Adenine, guanine
• Two kinds of sugars
– RNA – ribose
– DNA – deoxyribose
Nucleic Acids
• Nucleotides are linked
together by phosphodiester
linkages
– Covalent bond between a
phosphate group and a sugar
• This creates the sugarphosphate backbone
• One end will have a phosphate
attached to a 5’ carbon; the
other will have a hydroxyl group
on a 3’ carbon (these are the
ends of DNA and this plays a
role in replication)
• The opposing sides of DNA
are linked via hydrogen
bonds and twist about an
imaginary axis creating the
double helix
ATP
• Adenosine Triphosphate
– Organic molecule consists of an
adenosine molecule attached to a
string of 3 phosphate groups
– A reaction with water causes the
release of one of the phosphate groups
also releasing energy.
• Molecule becomes ADP
– Notice the similarities between ATP
and nucleic acids