If a mutation in a gene caused a hydrophobic amino acid in a polypeptide to be replaced by a hydrophilic amino acid, the most accurate statement among the options you provided would be:
The new amino acid would not form the same interactions with hydrophobic R groups, and the protein's shape would likely be affected.
Here's a brief explanation of why this is the most fitting choice:
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Amino Acid Properties: Hydrophobic (water-repelling) and hydrophilic (water-attracting) amino acids have different properties that affect how they interact with each other and their environment. A hydrophobic amino acid typically resides in the interior of a protein, away from the aqueous environment, while a hydrophilic amino acid is more likely to be on the exterior, interacting with water and other polar molecules.
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Protein Structure: The primary structure of a protein (the sequence of amino acids) dictates its secondary, tertiary, and quaternary structures. Changes in the primary structure can lead to changes in the way a protein folds, and this can ultimately affect its stability and functionality.
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Shape and Function: Altering just one amino acid can have significant effects on the protein's three-dimensional shape, which is crucial for its functionality. If this change disrupts important interactions (like hydrophobic interactions) that stabilize the protein, it can lead to loss of function or dysfunction.
The other options provided have inaccuracies:
- The claim that the hydrophilic amino acid could not form the proper peptide bond is incorrect as peptide bonds form between the amino group of one amino acid and the carboxyl group of another, regardless of their side chain properties.
- The idea that there would be no effect due to quaternary structure overlooks the fundamental principle that primary structure influences all subsequent levels of protein organization.
- The assertion that a single change would not affect the shape of the protein is misleading, as even one amino acid substitution can lead to significant changes in structure and function.
In summary, the replacement of a hydrophobic amino acid with a hydrophilic one is likely to alter the protein's shape due to changes in interaction patterns, ultimately affecting its function.
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