Explain why Na2CO3 (stop solution) inhibits -galactosidase activity.
Na2CO3, also known as sodium carbonate, is a commonly used chemical substance that can inhibit the activity of certain enzymes, including β-galactosidase. β-galactosidase is an enzyme that catalyzes the hydrolysis of lactose into glucose and galactose. When Na2CO3 is added to a reaction mixture, it can disrupt the enzyme's activity by altering the pH.
To understand why Na2CO3 inhibits β-galactosidase activity, we need to consider the enzyme's optimal pH range. Each enzyme has an ideal pH at which it functions most effectively. In the case of β-galactosidase, the optimal pH is typically around 7-8.
Na2CO3 is a basic compound, meaning it has a pH higher than 7. When Na2CO3 is added to a reaction mixture containing β-galactosidase, it raises the pH of the solution, moving it further away from the enzyme's optimal pH range. This alteration in pH can disrupt the enzyme's structure and affect its ability to bind to the substrate (lactose) properly.
Enzymes have specific three-dimensional structures that are crucial for their activity. Small changes in pH can cause alterations in the enzyme's structure, potentially disrupting its active sites. Since the active sites of β-galactosidase are responsible for binding to lactose and catalyzing its hydrolysis, any structural changes caused by Na2CO3 can significantly impair the enzyme's ability to function.
Therefore, the addition of Na2CO3 as a stop solution inhibits β-galactosidase activity by altering the pH and disrupting the enzyme's structure, ultimately preventing it from performing its catalytic function effectively.