Statement (I) : On hydrolysis, oligo peptides give rise to fewer number of α-amino acids while proteins give rise to a large number of β-amino acids.
Statement (II) : Natural proteins are denatured by acids which convert the water soluble form of fibrous proteins to their water insoluble form.
In the light of the above statements, choose the most appropriate answer from the options given below :
A
Both statement I and statement II are correct
B
Statement I is incorrect but Statement II is correct
C
Both statement I and statement II are incorrect
D
Statement I is correct but Statement II is incorrect
Answer
Correct answer:C
Step-by-step solution
Standard Method
Given: Two statements about hydrolysis of oligopeptides and proteins, and protein denaturation by acids.
Find: Which option correctly identifies the truth value of Statement (I) and Statement (II).
Statement (I): On hydrolysis, oligopeptides give fewer number of α-amino acids while proteins give a large number of β-amino acids.
Oligopeptides are short chains of amino acids, so on hydrolysis they yield their constituent amino acids. Proteins are also made of amino acids and on complete hydrolysis they also yield amino acids of the same fundamental type present in natural proteins, namely α-amino acids.
Thus, the claim that proteins give rise to a large number of β-amino acids is incorrect. Therefore, Statement (I) is incorrect.
Statement (II): Natural proteins are denatured by acids which convert the water soluble form of fibrous proteins to their water insoluble form.
Acids can denature proteins, but the statement is incorrect because it specifically refers to fibrous proteins becoming water-insoluble. Fibrous proteins are generally already water-insoluble, and the statement gives a misleading description of denaturation and solubility change.
Therefore, Statement (II) is also incorrect.
Hence, both Statement I and Statement II are incorrect. The correct option is C.
Step-by-step Evaluation
Given: Evaluate Statement (I) and Statement (II).
Find: The most appropriate option.
Analyze Statement (I).
Oligopeptides are short chains of amino acids linked by peptide bonds.
Hydrolysis breaks these peptide bonds and gives the constituent amino acids.
These are α-amino acids.
Proteins are long chains of amino acids, and on hydrolysis they also yield α-amino acids, not β-amino acids.
So, Statement (I) is incorrect.
Analyze Statement (II).
Acids do denature proteins by disrupting higher-order structure.
However, the statement specifically says acids convert the water-soluble form of fibrous proteins to water-insoluble form.
This is misleading because many fibrous proteins are already insoluble in water.
Denaturation is not correctly described here in terms of fibrous proteins.
So, Statement (II) is incorrect.
Match with the options.
The option stating that both Statement I and Statement II are incorrect is option (3).
Therefore, the correct option is C.
Common mistakes
Assuming that proteins yield β-amino acids on hydrolysis is incorrect because natural peptides and proteins are built from α-amino acids. Always recall the type of amino acid involved in peptide bond formation before judging the statement.
Thinking that denaturation specifically converts fibrous proteins from water-soluble to water-insoluble form is wrong because many fibrous proteins are already insoluble. Instead, focus on the general meaning of denaturation: loss of native structure and biological activity.
Judging Statement (II) only from the phrase that acids denature proteins can lead to an incorrect choice. A statement must be fully correct, so check whether the solubility claim and the protein type mentioned are also accurate.
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