The correct option for the sequence of protein hydrolysis is D. 3 → 4 → 1 → 2. Explanation of the Correct Answer To understand why option D is correct, we need to break down the process of protein hydrolysis step by step:

1. Proteins (3): Proteins are large, complex molecules made up of long chains of amino acids. They are the starting point in the hydrolysis process.
2. Peptones (4): When proteins undergo hydrolysis, they are broken down into smaller fragments called peptones. This process involves the action of enzymes (like proteases) or acidic conditions that cleave the peptide bonds between amino acids. Peptones are soluble in water and are smaller than whole proteins but still consist of multiple amino acids linked together.
3. Polypeptides (1): As hydrolysis continues, peptones can be further broken down into polypeptides. Polypeptides are shorter chains of amino acids, typically containing fewer than 50 amino acids. They are still larger than individual amino acids but represent a further breakdown of the protein structure.
4. Amino Acids (2): Finally, the hydrolysis process results in the formation of free amino acids. These are the building blocks of proteins and can be used by the body for various functions, including the synthesis of new proteins.

Thus, the correct sequence of protein hydrolysis is: - Start with Proteins (3), - Break down into Peptones (4), - Further break down into Polypeptides (1), - Finally, yield Amino Acids (2). Why Other Options Are Incorrect

• Option A (3 → 1 → 2 → 4): This sequence incorrectly suggests that proteins break down directly into polypeptides, then into amino acids, and finally into peptones. This is not accurate because peptones are an intermediate product formed before polypeptides.
• Option B (3 → 2 → 4 → 1): This option suggests that proteins break down directly into amino acids, which is incorrect. Amino acids are the end products of hydrolysis, not an intermediate step. Peptones and polypeptides must be formed first.
• Option C (3 → 1 → 2 → 4): This option also incorrectly places polypeptides before amino acids, suggesting that polypeptides are formed before amino acids, which is correct, but it fails to include peptones in the sequence, making it incomplete.

Summary of Key Points

• Protein Hydrolysis: The process of breaking down proteins into smaller units through the action of enzymes or acids.
• Sequence: The correct order is Proteins (3) → Peptones (4) → Polypeptides (1) → Amino Acids (2).
• Intermediate Products: Peptones and polypeptides are crucial intermediates in the breakdown of proteins to amino acids.
• Importance of Amino Acids: They are the final products of hydrolysis and are essential for various biological functions, including protein synthesis.

This detailed breakdown should help clarify the process of protein hydrolysis and reinforce the correct sequence.