Amino acids and proteins p1.
Amino acids are building blocks of proteins.
They are organic compounds that contain amine and carboxyl functional groups, along
with a side chain specific to each amino acid.
As shown above amino
acids have 4 groups attached to it:
i. Basic amino group (-NH2)
ii. Acidic carboxyl group (-COOH)
iii. Hydrogen atom
iv. Side chain (-R)
R group gives each amino acid its identity.
o Example:
, At physiological pH (~pH = 7.4): What is physiological pH?
o Carboxyl group gets dissociated (or
deprotonated) forming a negatively charged The pH that
carboxylate ion (COO-) normally prevails
o The amino group gets protonated. (- NH3+) in the human
body. It is
approximately
7.4.
Protonated – the
addition of a proton to an
atom, molecule, or ion.
Dissociation - general
process in which
molecules separate or
split into smaller particles.
Deprotonated – the
removal of a proton (H+)
from an acid.
L and D amino acids:
o They are amino acids that contains a chiral carbon atom (or also called
Asymmetric carbon atom) and undergoes optical isomerism.
o Glycine doesn’t contain an asymmetric carbon atom (chiral carbon atom).
1.
Why?
Glycine is a neutral amino acid (it has same no of
amine and acid groups). So, it has a carbon atom
attached to one amine, one acid and two Hydrogen
atoms therefore making it achiral
o Contains two isomers that are non-superimposable on one another. Therefore,
they are called enantiomers.
o From the two amino acid optical isomers, one Enantiomers – chiral
is: molecules that are mirror
1. D-amino acids – amino acids that can images of one another.
rotate the plane of polarized light to
Non-superimposable – the
the right. (Dextrorotatory)
molecules cannot be placed
2. L-amino acids – amino acids that can
on top of one another and
rotate the plane of polarized light to
give the same molecule.
the left. (Levorotatory)
o Only L-amino acids are present in human
proteins.
,
Amino acids are building blocks of proteins.
They are organic compounds that contain amine and carboxyl functional groups, along
with a side chain specific to each amino acid.
As shown above amino
acids have 4 groups attached to it:
i. Basic amino group (-NH2)
ii. Acidic carboxyl group (-COOH)
iii. Hydrogen atom
iv. Side chain (-R)
R group gives each amino acid its identity.
o Example:
, At physiological pH (~pH = 7.4): What is physiological pH?
o Carboxyl group gets dissociated (or
deprotonated) forming a negatively charged The pH that
carboxylate ion (COO-) normally prevails
o The amino group gets protonated. (- NH3+) in the human
body. It is
approximately
7.4.
Protonated – the
addition of a proton to an
atom, molecule, or ion.
Dissociation - general
process in which
molecules separate or
split into smaller particles.
Deprotonated – the
removal of a proton (H+)
from an acid.
L and D amino acids:
o They are amino acids that contains a chiral carbon atom (or also called
Asymmetric carbon atom) and undergoes optical isomerism.
o Glycine doesn’t contain an asymmetric carbon atom (chiral carbon atom).
1.
Why?
Glycine is a neutral amino acid (it has same no of
amine and acid groups). So, it has a carbon atom
attached to one amine, one acid and two Hydrogen
atoms therefore making it achiral
o Contains two isomers that are non-superimposable on one another. Therefore,
they are called enantiomers.
o From the two amino acid optical isomers, one Enantiomers – chiral
is: molecules that are mirror
1. D-amino acids – amino acids that can images of one another.
rotate the plane of polarized light to
Non-superimposable – the
the right. (Dextrorotatory)
molecules cannot be placed
2. L-amino acids – amino acids that can
on top of one another and
rotate the plane of polarized light to
give the same molecule.
the left. (Levorotatory)
o Only L-amino acids are present in human
proteins.
,
