B3 : Biological molecules

Question 1

Food test for carbohydrates (Starch)

Answer 1

1. Iodine Test
2. Add a few drops of iodine solution to the food sample
3. If starch is present (positive), solution will turn blue-black
4. If starch is absent (negative), the solution will remain yellowish-brown

Question 2

Food test for Carbohydrates (sugars)

Answer 2

1. Benedict’s Test
2. Add the sample into a test tube
3. Add an equal volume of Benedict’s solution to the test tube
4. Shake the test tube to mix the contents
5. Place test tube in a boiling water bath for 2 to 5 minutes
6. If sugars are present (positive), the solution will turn red, orange, or green
7. If sugars are absent (negative), the solution will remain blue

Question 3

Food test for proteins

Answer 3

1. Biuret test
2. Add the sample into a test tube
3. Add an equal volume of sodium hydroxide solution
4. Shake the test tube to mix the contents
5. Add copper II sulfate solution drop by drop shaking after each drop
6. If protein is present (positive), the solution will turn pinky purple
7. If protein is absent (negative), the solution will remain blue

Question 4

Food test for fats (lipids)

Answer 4

1. Ethanol emulsion test
2. Add the sample into a test tube
3. Add an equal volume of ethanol
4. Shake the test tube to mix the contents
5. Add water
6. If fat is present (positive), a white emulsion will form and it will be cloudy
7. If fat is absent (negative), the solution will remain clear

Question 5

Macromolecules of carbohydrates

Answer 5

1. Polymer: Polysaccharide (e.g. starch)
2. Monomer: monosaccharide (e.g. glucose/fructose)
3. Element: CHO (Carbon, Hydrogen, Oxygen)

Question 6

Macromolecules of lipids

Answer 6

1. Polymer: Triglyceride (e.g. animal fat)
2. Monomer: fatty acids
3. Element: CHO (Carbon, Hydrogen, Oxygen)

Question 7

Macromolecules of Proteins

Answer 7

1. Polymer: Polypeptide (e.g. enzymes)
2. Monomer: amino acids
3. Element: CHON (Carbon, Hydrogen, Oxygen, Nitrogen)

Question 8

Polymer

Answer 8

chain of monomers

Question 9

Monomer

Answer 9

most basic subunit of a larger substance/single unit of a larger molecule

Question 10

Elements in a macromolecule

Answer 10

the molecules that make up a macromolecule

Question 11

macromolecules

Answer 11

1. protein
2. carbohydrates
3. lipids

Question 12

Water

Answer 12

1. Needed for cells and body fluids
2. Transports dissolved substances around the body
3. Provides a medium for chemical reactions
4. Found in fruit juice, milk, and water
5. Important as a solvent