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Organic
Amino acids
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What are the two functional groups of amino acids
NH2
and
COOH
Amine
and
carboxylic acid
How many naturally occurring amino acids are there in the body
20
What type of amino acids are found in the body
Alpha
amino acids
It means that the
NH2
is ALWAYS on the
CARBON
next to the
COOH
Draw a
general
formula for alpha amino acids
,
Are alpha amino acids CHIRAL
YES
One carbon has
four
different substituents
EXCEPT
GLYCINE
where
R=H
Which enatiomer do alpha amino acids exist as in nature
NEGATIVE
enantiomer
How can amino acids be synthesised industrially
RCHO
+
NH4CN
->
RCH(NH2)CH
via
NUCLEOPHILLIC ADDITION
RCH(NH2)CN
+
HCl
+
2H2O
->
RCH(NH2)COOH
+
NH4Cl
Hydrolysis
and
HCl
is
DILUTE
Need to
REFLUX
the reaction mixture
Is the product from amino acids being synthesised naturally optically active
NO
A racemic mixture is formed when CN- ions can attack from above and below the planar C=C bond with equal likelihood
An equal amount of each enantiomer is formed, so no net effect on plane polarised light
In what form do amino acids exist as solids
ZWITTERIONS
because it is an ionic lattice they have a
HIGH melting
and
boiling point
What colour solids are most zwitterions at room temperature
white
solid
Do zwitterions dissolve in water
YES
But
NOT
in
NON-POLAR
solvents
Due to the
ionic
nature and
polar
bonds
define a zwitterion
Ions which have both a
permanent positive
and
negative
charge, but are overall
NEUTRAL
How do zwitterions occur in amino acids
COOH is
DEPROTONATED
->
COO-
NH2 is
protonated
->
NH3+
What happens to amino acids in ACIDIC conditions
GAINS
A
PROTON
ON
NH2
GROUP
What happens to amino acids in ALKALINE conditions
LOSES
A
PROTON
FROM THE
COOH
GROUP
What is the peptide linkage
-CONH-
What is a dipeptide
Two
amino acids
bonded
together
What name is given to chains of amino acids up to 50 amino acids
polypeptides
What is the name given to chains of amino acids with more than 50 amino acids
proteins
What are polypeptides used for
Enzymes
Wool
Hair
Muscles
What is the process called where polypeptides are broken down
hydrolysis
What conditions are needed for hydrolysis to occur
6
moldm^
-3
HCl
Reflux for
24
hours
What is the primary structure of a protein
the
sequence
of
amino acids
along the
protein chain
, bonded by
Covalent
bonds
How is the primary structure represented
Sequence of
3
letters abbreviations of the
amino acids
How can the primary structure of a protein be broken up
Hydrolysis
6M
HCl
24
hour reflux
What is the secondary structure of a protein
the
shape
of the
protein
chain
What are the two shapes an amino acid can form in the secondary structure
Alpha helix
shape
Beta pleated sheets
How is the secondary structure held together
Hydrogen
bonding
E.g between
C=O
and
N-H
groups
What is the tertiary shape of a protein
Alpha helix
or
beta pleated sheets
is folded into a
COMPLEX
3D
shape
How is the tertiary structure held together
Hydrogen
bonding
Ionic
interactions between
R
groups
Disulfide
bridges
Van der waals
forces of attraction
Why is the tertiary structure important
The
shape
of protein molecules is vital in their
function
e.g enzymes
How can amino acids be attracted to each other
Hydrogen
bonding
Ionic
interactions between groups on the side chain
Disulfide
bridges ->
2
S atoms oxidised to form an
S-S
bond
What is wool
A
protein fibre
in the secondary structure of
alpha-helix
held together by
hydrogen
bonds
What does wool's structure and bonding mean for wools properties
Can be
stretched
, as
H
bonds
extend
You can
release
it after stretching it and it returns to its
original
shape
If you wash it
TOO hot
the H bonds
PERMANENTLY
break so the clothes will
lose
its shape
What is a TLC plate made of
Plastic sheet coated with
silica
,
SiO2
This is the
stationary
phase
Describe how you would carry out THIN LAYER CHROMATOGRAPHY
spot the samples onto a
pencil line
a few cm above the base of the TLC plate
Place this in a
beaker
, with solvent level
below
the pencil line
Ensure there is a
lid
on the beaker to keep the inside
saturated
with solvent
vapour
Wait until the solvent front is almost at the
top
of the TLC plate; then remove it from the beaker then
analyse
Why does TLC
separate
amino acids
Solvent
carries amino acids up the
TLC plate
The rate of
movement
depends on the
balance
between the amino acid's
affinity
for the
solvent
and the
affinity
for the
stationary
phase
What do you often have to do to enable the amino acid to be seen on the chromatogram
Shine UV light
How do you calculate an Rf value
Distance moved by the
substance
/ distance moved by
solvent front
How can Rf values which amino acid is which
Compare the experimental
Rf Values
to known/accepted values in the
same solvent
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