Biological Molecules Question And Answers

Question 1

4. (b) Explain five functions of triglycerides (fats) in animals. [5]

Answer 1

1. Energy storage: Triglycerides store energy that can be used by animals.
2. Insulation: Fats provide thermal insulation, helping to maintain body temperature.
3. Protection: Fat pads protect vital organs like the kidneys.
4. Hormone production: Some hormones are produced from cholesterol, a type of lipid.
5. Cell membrane structure: Lipids are essential components of cell membranes.

Question 2

4. (d) Fats and oils are lipids. How do fats and oils differ? [2]

Answer 2

Fats are solid at room temperature, while oils are liquid at room temperature.

**

Question 3

5. What do the chemical structures of carbohydrates and fats have in common? How does their chemical structure differ? [4]**

Answer 3

Both carbohydrates and fats contain carbon, hydrogen, and oxygen.
Carbohydrates have a general formula of (CH2O)n, while fats have a glycerol molecule attached to three fatty acid chains.

**

Question 4

6. Give two safety precautions you would take when carrying out the Benedict’s test for glucose. [2]

Answer 4

**
1. Wear safety goggles to protect eyes from chemicals.
2. Handle hot solutions with care to prevent burns.

Question 5

**7. From this list, circle the carbohydrate(s) that is(are) transported in phloem. [1]

Answer 5

fructose, glucose, sucrose

**

Question 6

8. The proteins we eat are different from those in our bodies. How do we get our proteins from the ones we eat? [3]**

Answer 6

Our body breaks down the proteins we eat into amino acids, which are then used to build new proteins.

**

Question 7

9. Seals have a very thick layer of fatty tissue (blubber) under the skin. In what way is this useful to them? [1]**

Answer 7

Blubber provides insulation and stores energy.

**

Question 8

10. Why is a polysaccharide such as starch a convenient way of storing energy? [3]**

Answer 8

Starch is a complex carbohydrate that can be easily broken down to release energy when needed.

Question 9

12. Peas and beans belong to the same plant group, legumes. Seeds of legumes are known to contain proteins. Describe a practical test you could carry out on a fresh pea seed to show it contains protein. [5]

Answer 9

1. Crush the pea seed to form a powder.
2. Add a few drops of water to the powder to make a paste.
3. Add a few drops of Biuret reagent to the paste.
4. Shake the test tube gently.
5. Observe the color change.

**

Question 10

13. Which chemical elements are always found in proteins? [4]**

Answer 10

Carbon, hydrogen, oxygen, nitrogen

Question 11

14. Describe how you would carry out a test to compare the vitamin C content of two fruit juice samples. [5]

Answer 11

1. Label two test tubes as sample A and sample B.
2. Add an equal volume of each fruit juice sample to the respective test tubes.
3. Add a few drops of DCPIP solution to each test tube using a dropper.
4. Gently shake the test tubes and observe any color change.
5. The sample that retains the blue color of DCPIP has a higher vitamin C content.

Question 12

15. Outline how a test can be carried out to test for the presence of starch in food. [4]

Answer 12

1. Prepare a food sample by mashing it and mixing with water.
2. Transfer a small amount of the sample to a test tube.
3. Add a few drops of iodine solution to the test tube.
4. Gently shake the test tube and observe the color change.
   
   • Blue-black color indicates the presence of starch.