Cell level systems Study Guide

Enzymes are biological catalysts, meaning they speed up the rate of biochemical reactions without being used up themselves. Their activity is highly sensitive to environmental conditions such as temperature and pH. Each enzyme has an optimum temperature and pH at which its activity is maximal. Outside these optimal ranges, their activity decreases significantly, and extreme conditions can lead to denaturation, where the enzyme's active site changes shape, preventing it from binding to its substrate. This change is often irreversible. Standard experiments to investigate enzyme activity involve measuring the rate of a reaction by tracking the disappearance of a substrate or the appearance of a product over time. For example, investigating the effect of temperature on amylase activity (PAG B3) involves setting up multiple reaction mixtures at different temperatures using water baths. The time taken for starch to be completely broken down by amylase is measured using an iodine indicator to monitor the disappearance of starch. Similarly, to investigate the effect of pH, buffer solutions of different pH values are used to maintain a constant pH for each reaction mixture. Careful control of variables such as enzyme concentration, substrate concentration, and reaction volume is crucial to ensure that only the independent variable (temperature or pH) is affecting the reaction rate. Safety precautions such as wearing eye protection and handling chemicals safely are important in these practicals.