Carbohydrates and Lipids

This section explores the fundamental building blocks of carbohydrates and lipids, focusing on the concepts of monomers, polymers, and their various types.

Monomer and Polymer

A monomer is a small molecule that can bind to other similar molecules to form a larger structure. This larger structure formed by the joining of monomers is called a polymer.

Carbohydrates

Carbohydrates are organic compounds composed of carbon, hydrogen, and oxygen, typically in a ratio of $C_n H_m O_p$ (where n, m, and p are integers). They serve as a primary source of energy for living organisms.

Types of Monosaccharides

Monosaccharides are the simplest form of carbohydrates and are the monomers from which polysaccharides are formed. Common examples include:

• Glucose: A six-carbon sugar, the primary source of energy for cells.
• Fructose: A six-carbon sugar found in fruits.
• Galactose: A six-carbon sugar found in milk.

Types of Disaccharides

Disaccharides are formed when two monosaccharides are joined by a glycosidic bond. Examples include:

• Sucrose: Glucose + Fructose (table sugar)
• Lactose: Glucose + Galactose (found in milk)
• Maltose: Glucose + Glucose (malt sugar)

Types of Polysaccharides

Polysaccharides are large polymers composed of many monosaccharides linked together. They can be either homopolysaccharides (made of only one type of monosaccharide) or heteropolysaccharides (made of more than one type of monosaccharide).

Polysaccharide	Monosaccharide Composition	Function
Starch	Glucose	Energy storage in plants
Glycogen	Glucose	Energy storage in animals (primarily in the liver and muscles)
Cellulose	Glucose	Structural component of plant cell walls
Chitin	N-acetylglucosamine	Structural component of fungal cell walls and insect exoskeletons

Lipids

Lipids are a diverse group of hydrophobic (water-repelling) molecules. They are essential for energy storage, insulation, and cell structure.

Types of Monoglycerides

Monoglycerides are the simplest lipids, consisting of a glycerol molecule and one fatty acid molecule.

Types of Diglycerides

Diglycerides consist of a glycerol molecule and two fatty acid molecules.

Types of Triglycerides

Triglycerides are the most common type of lipid and consist of a glycerol molecule and three fatty acid molecules. They are primarily used for energy storage.

Lipid	Composition	Function
Fatty Acids	Long hydrocarbon chains with a carboxyl group at one end.	Component of triglycerides, cell membranes, and signaling molecules.
Glycerol	Three-carbon alcohol.	Backbone of triglycerides and phospholipids.
Phospholipids	Glycerol + two fatty acids + phosphate group.	Major component of cell membranes.
Steroids	Four fused carbon rings.	Hormones (e.g., testosterone, estrogen), cholesterol.