Unit 5

Macromolecules

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