Carbohydrates are organic molecules composed of carbon, hydrogen, and oxygen atoms, usually in the ratio of 1:2:1. They serve as a primary source of energy for living organisms and play essential roles in various cellular functions. Carbohydrates can be classified into three main groups: monosaccharides, disaccharides, and polysaccharides.

Monosaccharides:

Definition: Monosaccharides are the simplest form of carbohydrates and cannot be further hydrolyzed into smaller units. They consist of a single sugar molecule.
Examples: Glucose, fructose, and galactose are common monosaccharides. Glucose is a primary source of energy for cells, and it is utilized in cellular respiration.
Disaccharides:

Definition: Disaccharides are composed of two monosaccharide units linked together through a glycosidic bond.
Examples:
Sucrose: Glucose + Fructose (table sugar)
Lactose: Glucose + Galactose (found in milk)
Maltose: Glucose + Glucose (formed during the digestion of starch)
Polysaccharides:

Definition: Polysaccharides are large polymers made up of many monosaccharide units linked together. They serve as energy storage molecules or structural components.
Examples:
Starch: A polysaccharide found in plants, composed of glucose units. It serves as a storage form of energy.
Glycogen: A polysaccharide found in animals, particularly in the liver and muscles. It is a highly branched molecule and serves as a form of energy storage.
Cellulose: A structural polysaccharide found in the cell walls of plants. It provides rigidity and strength to plant cells. Humans lack the enzyme to digest cellulose.
Chitin: Found in the exoskeleton of arthropods and in the cell walls of fungi. It provides structural support.
Functions of Carbohydrates:

Energy Source: Carbohydrates are a primary source of energy for the body. Glucose, derived from the breakdown of carbohydrates, is utilized in cellular respiration to produce ATP (adenosine triphosphate).
Energy Storage: Excess glucose is stored in the form of glycogen in the liver and muscles (in animals) or as starch in plants.
Structural Support: Carbohydrates like cellulose and chitin provide structural support to cell walls in plants and fungi, as well as the exoskeleton of arthropods.
Cell Communication: Carbohydrates on the surface of cells play a role in cell recognition and communication.
Dietary Considerations:

Carbohydrates are a major component of the human diet. Sources include fruits, vegetables, grains, and legumes.
Simple carbohydrates (e.g., sugars) provide quick energy, while complex carbohydrates (e.g., starches and fibers) provide sustained energy and contribute to overall health.
Blood Sugar Regulation:

Insulin and glucagon, hormones produced by the pancreas, play a crucial role in regulating blood sugar levels by facilitating the uptake of glucose into cells or releasing stored glucose from the liver.