Functional group has specific properties, when attached to a larger molecule, in turn give the larger molecules specific properties.

1. BY Dr. EKHLAQUE
ekhlaquebiotech@gmail.com

2. Functional groups give specific properties
found together in a variety of different molecules.
Each functional group has specific properties that,
when attached to a larger molecule, in turn give
the larger molecules specific properties.
several functional groups in biology, including
alcohols, aldehydes, ketones, acids, amines,
phosphates, and thiols.

4.  An important biological molecules containing functional
groups is the amino acids, which have both a carboxyl group
and an amino group attached to the same carbon atom, called
the α carbon.
 Also attached to the α carbon atom are a hydrogen atom and a
side chain, or R group
 Different side chains have different chemical compositions,
structures, and properties.
 Each of the 20 amino acids found in proteins has a different
side chain that gives it its distinctive chemical properties.
 Because they possess both carboxyl and amino groups, amino
acids are simultaneously acids and bases.

5. Isomers have different arrangements of the
same atoms
Isomers are molecules that have the
same chemical formula but different
arrangements of the atoms.
(The prefix iso- meaning “same,”).
we will consider two: structural
isomers and optical isomers.

6. Structural isomers
It differ in how their atoms are joined together.
Consider two simple molecules, each composed
of 4 carbon and 10 hydrogen atoms bonded
covalently, both with the formula C4H10.
These atoms can be linked in two different ways,
resulting in two forms of the molecule:

7. Optical isomers
 The carbon atom has four different atoms or groups
attached to it.
This pattern allows two different ways of making the
attachments, each the mirror image of the other.
Such a carbon atom is an asymmetrical carbon, and the
pair of compounds are optical isomers of each other.
You can imagine your right and left hands as optical
isomers.
Just as a glove is specific for a particular hand, some
biochemical molecules can interact with one optical
isomer of a compound, but are unable to “fit” the other.

9. Cont…
The α carbon in an amino acid is an asymmetrical
carbon because it is bonded to four different
functional groups.
Therefore, amino acids exist in two isomeric
forms, called D-amino acids and L-amino acids.
D and L stand for right (dextro) and left (levo),
respectively.
Only L-amino acids are commonly found in most
organisms, and their presence is an important
chemical “signature” for life.

11. Molecules vary in size
Some are small, such as H2 and CH4.
Others are larger, such as a molecule of table
sugar (Sucrose, C12H22O11), which has 45
atoms.
Still other molecules, especially proteins
such as hemoglobin, are gigantic, sometimes
containing tens of thousands of atoms.