CARBOHYDRATES

Simple Sugars: The simplest carbohydrate is a single molecule of sugar. Simple sugars are soluable (dissolve) in water and often taste sweet. A single sugar unit is called a monosaccharide. Glucose, a sugar molecule containing 6 carbon atoms is an example of a carbohydrate. It can exist as either a straight chain of carbons or as a ring. Two other important sugars whose names we need to be familiar with are ribose and deoxyribose. They have 5 carbon atoms instead of 6 and are building blocks for nucleic acids (more details on them later).

Short-Chain Carbohydrates: A disaccharide is a short chain of two molecules resulting from the covalent bonding (remember we talked about this in the last lecture) of two monosaccharides. An example is sucrose (this is the kind of sugar you typically buy at the store) which is composed of a molecule of glucose plus a molecule of the sugar fructose (which has only five carbon atoms).

Complex Carbohydrates: When many sugars are covalently linked, they are called a polysaccharide. The most common polysaccharides are chains of glucose. Four important examples are starch, cellulose, glycogen and chitin. Starch is used for energy storage in plants. It's also what makes a baked potato taste so good. Starch is formed by a series of condensation reactions. The angular structures in this picture are grains of starch inside cells of a potato . Cellulose is found in plant cell walls. Glycogen is a storage form of glucose found in animal tissues. All three of these are composed of glucose units in different bonding arrangements. Chitin is the main structural material in the external skeleton of insects. It contains nitrogen atoms, in addition to carbon, hydrogen and oxygen.

This animation (AUDIO - IMPORTANT) describes how condensation and hydrolysis reactions occur. Condensation and hydrolysis are used to put together and break apart many biological molecules.

REVIEW:The following is composed of a 1:2:1 ratio of carbon to hydrogen to oxygen?
Answer carbohydrate