Macromolecules Flashcards
Macromolecule
very large molecule that consists of many structural units with similar chemical properties
Except for lipids, macromolecules are polymers
Polymers
A large molecule composed of multiple
repeating (chemically similar) subunits, called monomers –
that are attached to each other through covalent bonds.
monomer polymer
(chemically similar)
covalent bon
NAs
Nucleic acids are formed from four kinds of nucleotide monomers
(adenine, guanine, thymidine, cytosine) linked together by covalent bonds in
long chains
Proteins
formed from 20 kinds of amino acid monomers linked
together by covalent bonds in long chains.
amino acids protein
Proteins
(polymers)
Carbs
formed from monosaccharide (sugar)
monomers linked together by covalent bonds in giant structures.
Lipids
(not polymers)
formed from a small set of smaller molecules, but in
this case noncovalent forces maintain the interactions between
the fatty acid monomers.
Condensation reactions form polymers from monomers
(polymerization).
Hydrolysis reactions break down polymers into monomers.
monomerH OH monomerH OH
H2O
monomerH monomer OH
+
Molecular basis of polymer break down.
How many bonds does carbon form?
4 covalent bonds
What’s a covalent bond
Covalent bonds are formed when elements share electrons
Why do elements form bonds
To become stable.
They want to have a full outer shell.
Single pair of e-
Single covalent bond
2 pairs of e-
double bond
3 pairs of e-
triple bond
Carbon-carbon bond types
alkane
alkene
alkyne
Saturated Molecules
Alkanes are carbon-based molecules with single covalent bonds
between carbons. These are called saturated molecules.
There is a SINGLE covalent bond between
carbons.
This is a SATURATED molecule.
You cannot possibly add more H atoms to
this molecule
Single bonds = saturated
Unsaturated molecules
alkenes and alkynes are unsaturated molecules – alkenes have double bonds; alkynes have triple bonds. Unsaturated molecules
There are DOUBLE/TRIPLE
covalent bonds between carbons.
These are UNSATURATED
molecules.
These double or triple bonds can
be broken, and more hydrogen
atoms can be added to these
molecules.
Double/triple bonds = unsaturated
Why is electronegativity/polarity important in biology?
Polarity enables molecules to form hydrogen bonds.
Polar Molecules
Polar molecules have slightly more positive or negative
regions that can interact with water through hydrogen
bonding
These molecules are called ‘hydrophilic’ molecules
Non polar molecules
In non-polar molecules charge is equally
distributed throughout the molecule. =
They DO NOT HAVE slightly more
negative/positive regions that can interact
with water.
These molecules are called
‘hydrophobic’ molecules.
Non-polar molecules CANNOT form
hydrogen bonds with water.
How do functional groups confer hydrophobicity/
hydrophilicity?
in general, a functional group will make a macromolecule more
hydrophilic because most functional groups have polarity
(charge).
What’s a functional group
Groups of atoms in organic molecules that determine the
physical and chemical properties of molecules
Aromatic ring Structured hydrocarbons
typically
hydrophobic.
example: Benzene structure
Electronegativity
measure of the tendency of an atom to attract a bonding pair of electrons
Summary of electronegativity
*The higher the electronegativity, the more the atom likes to keep
hold of electrons.
* Electronegativity creates polar bonds (positive charge at one end,
negative charge at the other).
* Molecules that have polar covalent bonds can interact with water
through hydrogen bonding. These are hydrophilic molecules.
* Molecules that do not have polar bonds cannot interact with water
through hydrogen bonding. These are hydrophobic molecules
FGs on hydrophobicity etc
- Functional groups typically confer hydrophilic characteristics.
- Aromatic structures typically confer hydrophobic characteristics
Isomerism
The atoms in a functional group can be arranged differently –
which will result in differences in structural, functional and
chemical properties
Structural
Structural isomers are compounds that have the
same molecular formulae but different structural formulae.
Example 1: Butane and isobutane - C4H10
Geometric (cis-trans) isomers
cis- and trans- isomers are compounds that have the same atoms
connected to each other, however the atoms are differently
arranged in space.
Example 1: cis-2-Butene and trans-2-Butene - C4H8
2b- Optical isomerism
Optical isomerism occur when a carbon atom has four different
atoms or groups of atoms attached to it. This carbon is called the
chiral carbon (chiral centre).
Optical isomers are also known as ‘enantiomers’.
Chiral Carbon
Chiral carbon will have 4 different atoms/groups
attached to it.
How do we distinguish between optical isomers (enantiomers)?
By using light polarization.
D form (RHS) e.g Natural Sugars
D-form of the chiral sample (for example D-glucose)
(rotates the plane of polarized light to right - clockwise)
D comes from dextrorotary
L- Form (LHS) e.g AAs
L-form of the chiral sample (for example L-glucose)
(rotates the plane of polarized light to left - anticlockwise)
L comes from levorotary.
Summary of Plane Polarised Light
- Solutions of chiral chemical compounds
change the plane in which the light is
polarized. - Each enantiomer of a pair rotates the plane
of the light by the same amount, but the
directions of rotation are opposite. - If one enantiomer rotates the plane of the
light to the right (D-form), the other rotates
it to the left (L-form).
