LIPIDS : LIPIDS Lipids are also organic compounds containing carbon, hydrogen and oxygen. However, hydrogen and oxygen occur in a ratio much higher than in water. Lipids form about 3.5% of the total chemical composition of a cell.
Lipids are generally insoluble in water but soluble in organic solvents like ether and chloroform.
The biologically important lipids can be classified into 3 types namely simple lipids, compound lipids and derived lipids
Simple Lipids : Simple Lipids These are esters of fatty acids with various types of alcohol. They are distinguished into fats and oils.
Fats are esters of fatty acids and glycerol. A fatty acid is an organic acid with a hydrocarbon chain ending in a carboxyl (COOH) group. Most fatty acids have an even number of carbon atoms ranging between 14 to 22 (most commonly 16 or 18).
The carbon and hydrogen atoms form a long hydrocarbon tail that is hydrophobic (having no affinity for water).
Compound Lipids : Compound Lipids These are lipids, which contain an inorganic or organic group in addition to fatty acids and glycerol. They are of the following 3 types:
Phospholipids
These are lipids containing a phosphate group.
A phospholipid molecule has a strongly nonpolar and hydrophobic (water insoluble) tail region represented by fatty acid chains and a strongly polar or hydrophilic (water soluble) head region represented by the phosphate group. A Lipid Bilayer in an Aqueous Medium
Slide 4 : Glycolipids
These are lipids containing a carbohydrate group, usually galactose. They are found in the nerve cell membranes especially in the myelin sheath.
Lipoproteins
These are lipids, usually phospho-lipids which contain a protein molecule. They occur in the cell membrane. They are also found in milk and egg yolk.
Sterols
These are lipids that do not have a straight chain. They are composed of four fused carbon rings and a long hydrocarbon side chain. The most familiar example is cholesterol, which is abundant in animal cells.
Cholesterol is an essential component of animal cell membrane. It is a precursor of several steroid hormones produced in animals. It is also involved in the formation of bile salts and vitamin-D.
Amino Acids : Amino Acids Amino acids are compounds containing carbon, hydrogen, oxygen and nitrogen. They serve mainly as monomers (building blocks) of proteins.
An amino acid is represented by a general empirical formula R.CH.NH2. COOH. Each amino acid has at least an amino (NH2) group and a carboxyl (COOH) group. R is the function group, which varies from one amino acid to another.
There are about 20 amino acids that form the constituents of cell proteins. These are called protein amino acids. Many amino acids found in cells do not take part in the formation of proteins. These are called non-protein amino acids.
Amino acids are recognised into three groups based on their reaction in solution, namely
Slide 6 : Acidic Amino Acids
These have two carboxyl groups and one amino group. The free carboxyl group is acidic in nature. For example, aspartic acid and glutamic acid
Basic Amino Acid
These have two amino groups and one carboxyl group. The free amino group is basic in nature. For example, Lysine and Arginine.
Neutral Amino Acids
These have one amino and one carboxyl group. For example, alanine, glycine.
Nucleotides : Nucleotides Nucleotides are nitrogen containing organic compounds, which form the monomers of nucleic acids that are involved in the information transfer system of the cells.
They are also involved in the mechanism of energy transfer in cells.
A nucleotide is a compound containing carbon, hydrogen, oxygen, nitrogen, and phosphorous.
A molecule of a nucleotide is in turn composed of three smaller molecules phosphate (P) sugar (S) and nitrogen base (N).
Slide 8 : Components of Nucleic Acids
Slide 9 : THANK YOU