Carbohydrates

Carbohydrates

Carbon and Organic Molecules

Carbon has six protons and six electrons. Its four outer-shell electrons allow it to form up to four covalent bonds. Carbon can bond with elements such as hydrogen, oxygen, nitrogen, phosphorus, and sulfur, as well as with other carbon atoms. It can form single, double, or triple bonds, making it possible to build a variety of molecules and chains.

Polymers and Monomers

A monomer is a single subunit, while a polymer consists of many linked subunits. Polymerization joins monomers into larger molecules: two linked monomers form a dimer, three form a trimer, and so on.

In the carbohydrate examples discussed, monomers are joined through dehydration synthesis, in which water is removed as a bond forms between subunits.

Carbohydrate Composition and Functions

Carbohydrates contain carbon, hydrogen, and oxygen, usually in a 1:2:1 ratio. Glucose, for example, has the formula C₆H₁₂O₆. Carbohydrates can be represented as chains or rings; either representation can have the same chemical composition.

Carbohydrates help organisms store and release energy. They can also provide structural support or protection. The video emphasizes their role in short-term energy storage.

Monosaccharides

Monosaccharides are the simplest sugars:

• Glucose is a basic sugar used by cells.
• Fructose is one of the sugars in sucrose.
• Galactose is one of the sugars in lactose.

Disaccharides

Disaccharides consist of two linked sugar units. They form through dehydration synthesis, which removes water as the two units bond.

• Sucrose is table sugar and is associated with plants.
• Lactose is milk sugar, produced in mammary glands to nourish young mammals.
• Maltose is described as a plant-based sugar associated with seeds and fruit, where germination and ripening take place.

Polysaccharides

Polysaccharides consist of many linked sugar units. They form through dehydration synthesis, with water removed as each additional unit is attached.

• Starch is a plant polysaccharide made of glucose units oriented in the same direction, without branching. It functions in energy storage.
• Cellulose is a plant polysaccharide made of glucose units oriented in alternating directions, without branching. It provides structural support rather than storing energy and forms part of plant cell walls.
• Glycogen is an animal polysaccharide made of glucose units oriented in the same direction, with branches. It serves as a short-term energy-storage form in animals.

Speaker

Mr. P is the sole speaker and presenter.