Carbohydrates – Level 3 Applied Science BTEC Revision

Carbohydrates are biologically important macromolecules composed of carbon (C), hydrogen (H), and oxygen (O).
They are made from monosaccharides (simple sugars), with most common ones being glucose and fructose.
Two monosaccharides can combine to form a disaccharide (a double sugar) like sucrose, lactose, and maltose.
Polysaccharides are linked chains of monosaccharides forming complex carbohydrates such as starch, glycogen and cellulose.

Carbohydrates serve as a key source of energy for living organisms. Glucose, for example, is the primary energy source for cells.
Some carbohydrates, like cellulose in plants, provide structural support. In insects and crustaceans, the carbohydrate chitin forms a major part of their exoskeleton.
They also play a significant role in cell recognition and signalling due to the presence of carbohydrate chains on the surface of cell membranes, aiding in cell interaction and communication.

The process by which glucose is broken down to release energy is known as glycolysis.
In oxygen-rich conditions, the products of glycolysis move into the Krebs cycle to produce more energy.
Glucose can also be stored for future use in the form of glycogen in animals and starch in plants, in a process known as glycogenesis.
When energy is required, these polysaccharides can be broken down into glucose through glycogenolysis in animals and starch degradation in plants.

Carbohydrates should be the body’s main source of energy in a healthy, balanced diet.
Eating an excess of certain types of carbohydrates, notably simple sugars, can lead to obesity and related health problems such as type 2 diabetes.
Fibre, a type of indigestible carbohydrate found in foods such as whole grains and vegetables, is important for maintaining a healthy digestive system.