Name: Class: Date: Functional Groups and Biomolecules Functional groups are specific combinations of bonded atoms that always react in the same way, regardless of the particular carbon skeleton. Much of biomolecule’s chemistry can be attributed to its functional groups. In this lab exercise, you will construct and sketch the various functional groups. Procedure for the Chemistry of Carbohydrates: Students should work independently or in pairs. Each student is expected to complete his/her own worksheet with the following materials. 12 Carbon (C) -­‐ tetrahedral atoms (black) 26 Hydrogen (H) atoms (white) 13 Oxygen (O) – double electron atoms (blue) 26 Electron bonds (white tubes) I. Functional Groups: The four major groups of organic molecules found in cells are carbohydrates, fats, proteins, and nucleic acids. Inorganic substances found in cells are water, carbon dioxide, and oxygen. I.1. Construct a hydroxyl group and sketch it below (R – OH). I.2. Construct a carbonyl group and sketch it below (R – CO – R). I.3. Construct a carboxyl group and sketch it below (R – COOH). I.4. Sketch an amino group (R – NH2). I.5. Sketch a sulfhydryl group (R – SH). I.6. Sketch a phosphate group (R – OP(=O)(OH)2). Chemistry of Carbohydrates. Carbohydrates make up a large group of organic compounds found in cells. They are generally used for energy and found in cell structures. They are the simplest organic compounds consisting of carbon, hydrogen, and oxygen. With this lab exercise you will be able to construct a water molecules and three groups of carbohydrates (monosaccharides, disaccharides, and polysaccharides.) You will also be able to Name: Class: Date: distinguish differences in molecular and structural formulas and understand isomerism, synthesis and dehydration. II. Water: The chemical formula for water is H2O. Construct a water molecule. II.1. What elements make up water? II.2. Draw the structural formula for water. III. Carbohydrates: Saccharides are an important group of biological compounds. The man different types of sugars have been groups into three main categories: monosaccharides, disaccharides, and polysaccharides. III.1. Study the structural formula of the three monosaccharides in Fig. 1. III.2. Construct two different models of the monosaccharides. Join with another person so that all three monosaccharides are build and available to use. The models constructed represent the three-­‐dimensional shapes of the molecules. They illustrate that individual molecules of carbohydrates do differ from one another in general structural shape even though their molecular formulas are the same. They also will illustrate how it is possible for molecules to join together to form different carbohydrates. III.3. How many atoms of carbon are in each molecule of glucose? ______ fructose? ______ and galactose? _______ III.4. Write the molecular formula for glucose _______________ fructose ______________ and galactose _______________ III.5. Compare the number of hydrogen atoms to the number of oxygen atoms in each sugar. What is the ratio of hydrogen to oxygen? ___________ What is the ratio of hydrogen to oxygen in a molecule of water? _____________ III.6. Molecules of monosaccharides may have the same molecular formula but differ in three-­‐
dimensional structures. This is called isomerism. Describe isormerism in your own words. IV. Double Sugars or Disaccharides: Two monosaccharides can chemically join together to form a large carbohydrate molecule called a double sugar, or disaccharide. When a glucose Name: Class: Date: molecule chemically joins with another glucose molecule, a double sugar known as maltose is formed. When a glucose molecule joins with a fructose molecule, a different double sugar called sucrose is produced. IV.1. Attempt to join the glucose and fructose models to form sucrose. Will the sucrose model stay together? _________ IV.2. It will be necessary to remove an –OH end from one molecule and an –H end from another in order to join the molecules. Does this enable the two molecules to be joined together? __________ IV.3. Write the molecular formula for sucrose. IV.4. Construct a maltose molecule. Write its molecular formula. IV.5. What are the ratios of hydrogen atoms to oxygen atoms for both molecules? _____________ IV.6. Does isomerism exist in double sugars? _____________ IV.7. How many monosaccharide molecules are needed to form a disaccharide? _______________ IV.8. How many water molecules are removed to form a disaccharide? _______________ V. Complex Sugars or Polysaccharides: Just as double sugars were formed from two monosaccharides, complex sugars are formed when many single sugars are joined together chemically. The exact number of glucose molecules attached to form these polysaccharides is not known. The most common polysaccharides are starch and cellulose. They consist of long chains of glucose molecules joined together. V.1. With another team, construct a starch molecule by joining four glucose molecules. This represents only a small part of a starch molecule because starch consists of hundreds of glucose molecules. V.2. What must be removed from some of the glucose molecules in order to join them? ________ V.3. What is the chemical formula for your constructed polysaccharide? _________________________ V.4. How does the ratio of H to O atoms in starch compare with the ratio in double sugars? ____________ In single sugars? _______________ In water? ________________ VI. Interpretations VI.1. Synthesis means “the process by which simple compounds are united to form more complex materials.” Dehydration means “loss of water.” Explain why chemists refer to the joining of monosaccharide molecules to form disaccharides as a dehydration synthesis reaction. VI.2. Why is the joining of four glucose molecules to form a polysaccharide an example of dehydration synthesis? VI.3. The word carbohydrate is derived from carbon and water (hydrate). Explain why this combination correctly describes this chemical group?