Lipids and Their Functions

Lipids

• Lipids are organic compounds that are insoluble in water and soluble in organic solvents.
• They are involved in energy storage, cell membrane structure, hormone production, and other functions.

Fatty Acids

• There are saturated fatty acids which only contain single bonds between carbon atoms and unsaturated fatty acids which contain double bonds.
• Some fatty acids, like linoleic acid, linolenic acid, and arachidonic acid, are essential and must be obtained from the diet.

Glycerides

• Glycerides are lipid esters containing glycerol and fatty acids.
• There are monoglycerides, diglycerides, and triglycerides.
• Triglycerides are the most important component of fat cells.

Phosphoglycerides

• Phosphoglycerides are derived from glycerol and have a phosphate group attached.
• They are major components of cell membranes.
• Examples: phosphatidate, phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol.

Sphingolipids

• Sphingolipids are derived from sphingosine.
• They are important components of the myelin sheath.
• Examples: cerebroside, sulfatide, ganglioside, sphingomyelin.

Steroids

• Steroids are lipids that have a rigid, four-ring structure.
• They are essential for various functions including hormone production and cell membrane structure.
• Cholesterol is a crucial component of cell membranes.

Lipoproteins

• Lipoproteins are complexes that transport lipids in the blood.
• Their functions include transporting triglycerides, cholesterol, and regulating cholesterol levels.

Vitamins

• Vitamin D and K are lipid-soluble vitamins.
• They are crucial for various functions including bone health and blood clotting.

Proteins

• Proteins are large, complex molecules composed of amino acids.
• They are involved in catalysis, immunity, transport, and regulation.

Amino Acids

• There are 20 common amino acids used by humans.
• Essential amino acids cannot be synthesized by the body and must be obtained from the diet.
• Non-essential amino acids can be synthesized by the body.

Protein Structure

• The primary structure is the linear sequence of amino acids.
• The secondary structure involves alpha helix and beta sheet formations.
• The tertiary structure is the 3D shape of the protein, determined by interactions between amino acid side chains.
• The quaternary structure involves the arrangement of multiple polypeptide chains.

Protein Classification

• Proteins can be classified based on composition or function.
• Composition: Nucleoproteins, Glycoproteins, Phosphoproteins, Chromoproteins.
• Function: Structural (collagen, keratin), Contractile (myosin), Storage (albumin), Transport (hemoglobin), Regulatory (insulin, enzymes).

Protein Denaturation

• Protein denaturation involves the unfolding and rearrangement of protein structure.
• Factors contributing to denaturation: heat, pH changes, heavy metals, light.