Unit 5 Macromolecules

Molecules that make up living things Carbon-based molecules Carbohydrates Lipids Proteins Nucleic acids

Macromolecules, continued Composed of subunits called monomers Many monomers make a polymer Monomers linked by covalent bonds Process called dehydration synthesis (OR, condensation) because a water molecule is given off when the bond between monomers forms

Figure 3.3 Condensation and Hydrolysis of Polymers (Part 1)

Hydrolysis Breaking down polymers to monomers Requires addition of water molecule

Figure 3.3 Condensation and Hydrolysis of Polymers (Part 2)

Carbohydrates Sugars, starches Monosaccharides –Glucose Disaccharide –Sucrose –Formed by glucose covalently bonded to fructose Polysaccharides –Starch, glycogen, cellulose

Benedict’s test Benedict’s reagent tests for the presence of a free carbonyl group Sugars with a free carbonyl group are called reducing sugars Monosaccharides are reducing sugars Some disaccharides are reducing sugars

Method for Benedict’s Test 8 different substances for the presence of reducing sugars. Add Benedict’s reagent to substance, mix. Heat for 3 minutes in boiling water. Place all tubes in a beaker of boiling water. Use test tube tongs. Look for color change. –Orange-red is a positive reaction.

Iodine test for starch Starch is also a carbohydrate (a polysaccharide) Starch turns blue-black in the presence of iodine.

Lipids Lipids are insoluble in water Hydrophobic Lipids clump together in water Examples: –Fats, steroids, waxes, oils

Sudan IV test for lipids Observe what happens when oil is added to water Add 5 drops of Sudan IV and mix. In which of the liquids is the dye soluble? Add detergent to this mixture and mix. What happens to the pink color?

Proteins- Biuret Test Composed of monomers called amino acids Linked together by peptide bonds Biuret reagent reacts with the peptide bonds to change color from light-blue to violet. Test 8 substances for the presence of proteins

Figure 3.5 Formation of Peptide Linkages

Hydrolysis of macromolecules Polymers are broken down by hydrolysis reactions Bonds are broken by the addition of water Test what happens when starch and sucrose are hydrolyzed. Hydrolysis in this case is caused by –Boiling

Test for hydrolysis with no heat – Tubes # 1, 2, and 3. Test for hydrolysis by heating 10 minutes –Tubes # 4, 5, 6. Test for hydrolysis by heating 20 minutes – Tubes 7, 8, 9. For each set you will perform Benedict’s test and Iodine test.

Develop a hypothesis. In which tube would you expect to positive reaction for starch and reducing sugars? Why? (You will need to know which sugars are reducing sugars. Do some internet research this information.)

Complete chart of colorimetric tests