grade 9 biomolecules.pdf

Carbohydrate Chemistry There are three different groups of carbohydrates: monosaccharides, disaccharides and polysaccharides. "Saccharide" means sugar.

Group 1: Monosaccharides (single molecule sugars) A single molecule sugar is called a monosaccharide. The prefix "mono-" means one. However, the one molecule can have different shapes due to a different arrangement of atoms. Examples of three monosaccharides are glucose, fructose and galactose. Examine the structure formulas of these three sugars and answer questions 1 - 7.

1. What three chemical elements are present in the three monosaccharides shown? ______________ 2. How many atoms of carbon are present in a molecule of: glucose _______ fructose_______ galactose _____ 3. Add subscripts to the following to indicate the proper simple formula. Fill in the blanks by counting the total number of carbon, hydrogen, and oxygen atoms in each molecule. glucose C___H___ O___ fructose C___H___ O___ galactose C___H___ O___ 4. Are there two times as many hydrogen atoms than oxygen atoms in a molecule of: glucose _____ fructose _____ galactose _____ 5. Are there two times as many hydrogen atoms than oxygen atoms in a molecule of water? _____ 6. Compare the structural formula of glucose to fructose. a. Are they exactly the same shape? ______ b. Are they both monosaccharides? ______ 7. Glucose, fructose and galactose have the same chemical formula but different structures. This makes them ___________.

Group 2 Disaccharides (double molecule sugars) Two monosaccharide sugar molecules can join chemically to form a larger carbohydrate molecule called a double sugar or disaccharide. The prefix "di-" means two. Condensation is a reaction in which two molecules become covalently bonded to each other through the loss of a small molecule - usually water. Hydrolysis is a chemical process that splits molecules by the addition of water. 8. Cut out one model of glucose and one model of fructose along the solid lines. Can you find a way to make these paper models fit together? _____. 9. In order to join the molecules, cut along the dotted lines and remove one OH- from the end of one molecule and one H+ from the end of another. 10. Does removing the H+ and OH- ends now allow the molecules to fit together easily? _____ 11. The H+ and OH- ends that were removed can also fit together with each other to form a molecule. This new molecule has a simple formula of ______________ and is called ______________. 12. What is this process called?__________________ 13. Write a simple formula for sucrose by adding together the molecular formulas for glucose and fructose and then subtracting water, H2O (Use structural formulas for this step, not the models.) ____________________ Paste the sucrose model and water model in your notebook. Label them. Different disaccharide molecules can be made by joining other monosaccharides in different combinations. By chemically joining a glucose molecule with another glucose molecule, a double sugar called maltose is formed. Cut out and attempt to join two new glucose model molecules. 14. What must be removed from the glucose model molecules so they easily fit together? ______ 15. Write a simple formula for maltose ______________ 16. How does the simple formula for sucrose compare to maltose? _________ 17. Why is the formula for sucrose the same as maltose? _________________________________________________________________________ 18. How many monosaccharide molecules are needed to form one sucrose molecule?_________ 19. How many monosaccharide molecules are needed to from one maltose molecule?_________ Paste your maltose and water models into your lab book. Label them.

Group 3 Polysaccharides (many molecule sugars) Just as double sugars are formed from two single sugar molecules, polysaccharides are formed when many simple sugars are joined chemically. The prefix "poly-" means many. Starch, glycogen and cellulose are the three most common polysaccharides in biology. They consist of long chains of glucose molecules joined. Construct a starch molecule by joining three glucose molecules. This model will represent only a small part of a starch molecule because starch consists of hundreds of glucose molecules. Cut, paste and label. 20. What must be removed from the glucose model molecules in order to have them easily fit together.? _________ The simple formula for a polysaccharide is written as (C6H10O5)n. The n equals the number of times C6H10O5 is repeated.

Putting it together: 21. Glucose is the primary source of energy for cells. Foods rarely contain monosaccharides. What process is used in the digestion of disaccharides and polysaccharides to make glucose available to the cells? _____________________ 22. Cellulose, also called plant fiber, is an extremely long polysaccharide and very difficult to digest. Why? ________________________________________________________________

Carbohydrate cutouts Simulate condensation reactions by cutting these out and assembling them to make a disaccharide or polysaccharide according to the directions on the worksheet. Be sure to assemble water molecules as by-products of each reaction. Add this assignment to your table of contents.