Practice free Chemistry NEET multiple-choice questions online with instant answers and detailed explanations. No login required.
How many peptide linkages are present in a tripeptide?
The NCERT text mentions, 'A tripeptide contains three amino acids linked by two peptide linkages.' (Biomolecules_chemistry, page 292).
A protein is generally defined as a polypeptide with a molecular mass higher than 10,000 u and containing more than a certain number of amino acid residues. What is this number mentioned for amino acid residues?
The NCERT text defines it as, 'A polypeptide with more than hundred amino acid residues, having molecular mass higher than 10,000u is called a protein.' (Biomolecules_chemistry, page 293).
The distinction between a polypeptide and a protein is not always sharp. Which of the following examples illustrates this point?
The NCERT text states, 'Polypeptides with fewer amino acids are likely to be called proteins if they ordinarily have a well defined conformation of a protein such as insulin which contains 51 amino acids.' (Biomolecules_chemistry, page 293).
What is the N-terminal amino acid in a protein thread?
The NCERT Biology text explains, 'The left end represented by the first amino acid and the right end represented by the last amino acid. The first amino acid is also called as N-terminal amino acid.' (BIOMOLECULES_biology, page 112).
Chemically, what is a peptide linkage?
The NCERT text clearly states, 'Chemically, peptide linkage is an amide formed between –COOH group and –NH2 group.' (Biomolecules_chemistry, page 292).
If a protein undergoes a change in its primary structure, what is the consequence?
The NCERT text explains, 'Any change in this primary structure i.e., the sequence of amino acids creates a different protein.' (Biomolecules_chemistry, page 293).
Which of the following bonds is NOT directly involved in establishing the primary structure of a protein?
The primary structure is defined by the sequence of amino acids linked by peptide (amide) bonds, which are covalent. Ester bonds are not involved in linking amino acids in the primary structure.
Which of the following classes of enzymes is responsible for catalyzing the breaking of C-C, C-halide, or P-N bonds by hydrolysis?
According to the NCERT text, 'Hydrolases: Enzymes catalyzing hydrolysis of ester, ether, peptide, glycosidic, C-C, C-halide or P-N bonds.' Therefore, Hydrolases are responsible for this type of reaction.
An enzyme's activity is significantly reduced when a chemical whose molecular structure closely resembles the substrate competes for the enzyme's active site. This phenomenon is known as:
The NCERT text states: 'When the inhibitor closely resembles the substrate in its molecular structure and inhibits the activity of the enzyme, it is known as competitive inhibitor. Due to its close structural similarity with the substrate, the inhibitor competes with the substrate for the substrate-binding site of the enzyme.'
Which of the following components of an enzyme is an organic compound, tightly bound to the apoenzyme, and part of the active site, as seen in peroxidase and catalase?
The NCERT text specifies: 'Prosthetic groups are organic compounds and are distinguished from other cofactors in that they are tightly bound to the apoenzyme. For example, in peroxidase and catalase, which catalyze the breakdown of hydrogen peroxide to water and oxygen, haem is the prosthetic group and it is a part of the active site of the enzyme.'
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