Biomolecules are crucial for the proper functioning of living organisms, and they interact in complex ways to support life processes such as metabolism, growth, reproduction, and response to environmental changes. Understanding biomolecules is fundamental to the fields of biology, biochemistry, and molecular biology.

Carbohydrates are organic compounds composed of carbon, hydrogen, and oxygen atoms. They serve as a primary source of energy for living organisms and play essential roles in various cellular processes. Carbohydrates can be categorized into several types based on their structure and the number of sugar units they contain. Here are some common types of carbohydrates:

1. Monosaccharides: Monosaccharides are the simplest carbohydrates and consist of a single sugar unit. Common monosaccharides include:

   • Glucose
   • Fructose
   • Galactose

2. Disaccharides: Disaccharides are composed of two monosaccharide units linked together through a chemical bond called a glycosidic bond. Common disaccharides include:

   • Sucrose (glucose + fructose)
   • Lactose (glucose + galactose)
   • Maltose (glucose + glucose)

3. Oligosaccharides: Oligosaccharides are carbohydrates made up of a small number (typically 3 to 10) of monosaccharide units linked together. They are often found as components of larger complex carbohydrates like glycoproteins and glycolipids.

4. Polysaccharides: Polysaccharides are large, complex carbohydrates consisting of numerous monosaccharide units linked together. They serve various functions in organisms. Common polysaccharides include:

   • Starch: A storage polysaccharide in plants, composed of glucose units.
   • Glycogen: A storage polysaccharide in animals, primarily found in the liver and muscles, also composed of glucose units.
   • Cellulose: A structural polysaccharide in the cell walls of plants, made up of glucose units. Humans cannot digest cellulose, but it is a crucial component of dietary fiber.
   • Chitin: Found in the exoskeletons of arthropods (such as insects and crustaceans) and in the cell walls of fungi, composed of modified glucose units.

5. Hexoses, Pentoses, and Trioses: These are categorized based on the number of carbon atoms in the monosaccharide molecule.

   • Hexoses have six carbon atoms, and examples include glucose, fructose, and galactose.
   • Pentoses have five carbon atoms, and examples include ribose and deoxyribose, which are important components of nucleic acids (RNA and DNA).
   • Trioses have three carbon atoms, and an example is glyceraldehyde.

Carbohydrates serve as a primary energy source in the form of glucose, are used for energy storage (e.g., as glycogen in animals and starch in plants), and have structural roles (e.g., cellulose in plant cell walls). They also play a role in cell recognition, adhesion, and signaling in the form of glycoproteins and glycolipids.