Which of the following amino acid classifications are correctly matched?  1. Uncharged polar AA – Cysteine  2. Nonpolar AA – Histidine  3. Basic AA – Proline  4. Basic AA – Lysine

1. A

   A. A and B

2. B

   B. C and D

3. C

   C. B and C

4. D

   D. A and D

Appeared in: INI-CET EXAM -2026

Explanation

• Statement 1 is correct: Cysteine has a polar sulfhydryl (-SH) group in its side chain but carries no net charge at physiological pH, classifying it as an uncharged polar amino acid.
• Statement 4 is correct: Lysine's side chain contains a primary amino group that is protonated (positively charged) at physiological pH, making it a basic amino acid.
• The properties of amino acid side chains (polarity, charge) are fundamental to determining the three-dimensional structure and function of proteins.

Why Other Options Were Wrong

• Option A: This option is incorrect because it includes statement 2, which is false.
• Option B: This option is incorrect because it includes statement 3, which is false.
• Option C: This option is incorrect because it includes both statements 2 and 3, which are false.

Related Visual

Clinical Relevance

• Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Classification of amino acids based on side chain properties as background academic context rather than a clinical decision trigger.
• Understanding amino acid properties is crucial for comprehending protein structure and function. For example, the basic amino acid Histidine is often found in the active sites of enzymes where it acts as a proton donor or acceptor.
• Genetic diseases like Sickle Cell Anemia are caused by a single amino acid substitution (a polar glutamate is replaced by a nonpolar valine), drastically altering the protein's (hemoglobin) structure and function.
• The polarity of amino acids determines how a protein folds. Hydrophobic (nonpolar) amino acids tend to be buried in the protein's core, away from water, while hydrophilic (polar and charged) amino acids are typically on the surface.

How to Approach the Question

• This is a factual recall question requiring knowledge of biochemistry.
• First, analyze each of the four numbered statements independently.
• For each statement, determine if the amino acid is correctly matched with its classification (e.g., 'Is Cysteine an uncharged polar amino acid?').
• Mark each statement as either 'Correct' or 'Incorrect'.
• After evaluating all four statements, look at the options (A, B, C, D).
• Select the option that groups together the statements you identified as 'Correct'.

Concept Tested & Keywords

• Concept Tested: Classification of amino acids based on side chain properties
• Stem keywords: amino acid classifications, Uncharged polar, Nonpolar, Basic, Cysteine, Histidine, Proline, Lysine
• Lead-in keywords: correctly matched

Question ID

QViyGNOZj2r3V_ySAHH5E0

Copy ID

Reference Book

E6 Textbook of Biochemistry for medical StudentsDM Vasudevan Part 1 (pp 26-370 of 370) p. 96-98

E6 Biochemistry U Satyanarayana— Part 1 (pp 26-420 of 840) p. 36-38