Final answer:
A missense mutation can significantly impact protein function, especially if it occurs at a functionally crucial site like an enzyme's active site. The specific effects depend on the chemical properties of the substituted amino acid and its location in the protein. Sickle-cell disease is a classic example of how a single amino acid change can lead to a malfunctioning protein.
Step-by-step explanation:
Effects of Amino Acid Substitution in Proteins. Changing one amino acid in a protein sequence can lead to various effects on the protein's function. This type of mutation, known as a missense mutation, may result in an amino acid that has different chemical properties compared to the original. Depending on where the substitution occurs, such as in an active site of an enzyme, the protein might lose its functionality. A classic example is sickle-cell disease, where the substitution of glutamic acid with valine causes the hemoglobin protein to malfunction, leading to the disease's symptoms. Proteins are intricate molecules that rely on their precise amino acid sequences to function correctly. When the sequence is altered, even slightly, it can lead to structural changes or misfolding, which in turn affects the protein's capacity to perform its intended role within the body. In some cases, the mutated protein might retain some functionality, however, if the change is benign or occurs outside crucial regions. Conversely, if an enzyme's active site is altered, it may become unable to catalyze its reaction, potentially leading to the build-up of substrates or the absence of necessary products, which can be harmful.