Review notes: Bio 100 Spring 2002/Dennis Wilson
Chemistry of Life
Virtually all-living organisms, and therefore the cells that make them up, fall into several major types of chemicals. Living organisms are:
· 70-98% water (although water is NOT a chemical group, rather it is a compound)
· Nucleic acids
· Miscellaneous other stuff. This is a vital mix of many different types of chemicals.
Proteins: 10-100 million different kinds of protein in living organisms. Lipids and carbohydrates are not nearly so varied. It is this vast variety of proteins that contributes to the vast range of different functions proteins have and so the huge diversity of life on earth. Proteins are large complex molecules made from small building blocks called amino acids. There are about 20 different kinds of amino acids of importance to life’s processes. It is the number and sequence of different amino acids that give each protein its unique structure and therefore its unique properties. Remember structure-function relationships.
There are two different kinds of protein:
Carbohydrates: Plants and fungi are mostly composed of water and carbohydrate. They are the most abundant carbon containing compounds in living organisms. Carbohydrate literally means “carbon of water”. Thus carbohydrates have carbon C, hydrogen H, and oxygen O in a 1:2:1 ratio. For example, glucose is C6H12O6. Carbohydrates range in size from monosaccharides like glucose to disaccharides like sucrose (a glucose and fructose molecule joined) to huge polysaccharides like starch and cellulose that are composed of 100 or 1000s of glucose units.
Carbohydrates are used for energy storage:
Carbohydrates are used for structural purposes:
Lipids: This group includes fast, oils, waxes, phospholipids, and steroids. Generally, they are used as energy storage and as barriers or waterproof coatings. Each of the above type of lipid has it’s own structure and chemical composition. Let’s look at fats and oils: they have a glycerol backbone with three fatty acid chains. Where one or more fatty acid chains contain double bonds between carbons, they are unsaturated, generally liquid at room temperature, and considered oils that come mostly from plants. Fates are generally saturated and are found mostly in animals. Phospholipids have two fatty acid chains and a phosphate group on a modified glycerol backbone. The phosphate end is hydrophilic and the fatty acid chain end is hydrophobic. These form the bulk of cell membranes.