4.7.1 Proteins (Structured Question 1 & 2)


Question 1:
Diagram I shows two levels of organization in protein structure.





(a) In Diagram I, name the level of organization in the protein structures of P and Q.
(b) Describe the structure of protein P.
(c) Diagram II shows how protein P is broken down to form products.


(d) Explain how the products in Diagram II are formed.
(e) State why animal proteins are first class protein.

Silk is an example of protein. A silk garment crumples when it is washed using hot water at a temperature of 65OC.
(i) Explain the above statement.
(ii) Based on the above statement, suggest two ways to maintain the quality of silk garments.



Answer:
(a)
P: Primary structure
Q: Secondary structure

(b)
The linear sequence of amino acids in a polypeptide chain.

(c)
Protein P is broken down by an enzyme (polypeptidase) in hydrolysis to form dipeptides.

(d)
Because it contains all the 8 essential amino acids needed by humans. 

(e)(i)
Silk is a protein fibre. High temperatures will reduce the strength of the hydrogen bonds and disrupt the structure, thus denaturation of the protein occurs.

(e)(ii)
1.Wash it in cold water
2. Do not wring
3. Do not expose to direct sunlight
4. Never use chlorine bleach on silk
(Choose any 2)

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