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BIO1022: Textbook Summary - The Structure and Function of Large Biological Molecules

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THE STRUCTURE AND FUNCTION OF LARGE BIOLOGICAL MOLECULES The molecules of life o The four large molecules of all living things are: - Carbohydrates - Lipids - Proteins - Nucleic Acids o Carbohydrates, nucleic acids and proteins are large in size thus they are called macromolecules. Macromolecules o Macromolecules are chain-like molecules called polymers o A polymer is a long molecule which contains similar or identical building blocks linked by covalent bonds. o Monomers are the smaller molecules that act as a building block for polymers. Polymers o A condensation reaction is where two molecules are covalently bonded together and loses a water molecule. o It is also called dehydration reaction because a water molecule is lost. o The dehydration process is helped by enzymes, specialized macromolecules that speed up chemical reactions in cells. o Hydrolysis is the reverse of dehydration reaction. It is where a water molecule is added to break a bond. o Polymers are broken down to monomers due to hydrolysis. Carbohydrates o They act as fuel and building material. o They include sugars and polymers of sugars. o Monosaccharides are also known as simple sugars as it is the simplest carbohydrates. o Disaccharides are double sugars which has two monosaccharides joined by a dehydration reaction. o A disaccharide is two monosaccharides joined by a glycosidic linkage, a covalent bond formed between to monosaccharides by a dehydration reaction. o Polysaccharides are macromolecules that are polymers made up of many sugar building blocks. o Glucose is the most common monosaccharide. o During cellular respiration, cells use energy in a series of reactions starting with glucose molecules. Polysaccharide o Polysaccharides are macromolecules, polymers that contains hundreds to thousands monosaccharides joined by glycosidic linkage. o Polysaccharides either act as a storage material which is hydrolyzed to provide sugars for cells or act as a building material for structures that protects the cell or organism. o Plants store starch. o Animals store glycogen. o Cellulose is a polysaccharide that is a component of tough walls that surround the plant cells. o Chitin is a polysaccharide used by arthropods to build their exoskeletons. Lipids o The hydrophobic behaviour of lipids is due to their molecular structure. o Lipids includes: fats, phospholipids and steroids. Fats o A fat is made up of two kinds of smaller molecules: glycerol and fatty acids. o A fatty acid has a carbon at one end which is part of a carboxyl group. This functional group gives it the name of fatty acids. o Fats separate from water because the water molecules hydrogen- bond to one another and excludes the fats. o A saturated fatty acid is when there are no double bonds between carbon atoms to make the chain so hydrogen atoms are bonded to the carbon skeleton. o An unsaturated fatty acid has one or more double bonds formed by removing hydrogen atoms from the carbon skeleton. o The tails of the fat molecules has no double bonds which allow the fat molecules to pack closely together. Phospholipids o Phospholipids are important in cells because they make up cell membranes. o They only have two fatty acids attached to the glycerol. o The third hydroxyl group
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