Trypsin is an enzyme which catalyses the hydrolysis of casein, a protein found in milk. Milk that contains casein has a cloudy, white appearance. As the casein is hydrolysed by trypsin, the milk changes in appearance to a clear (transparent), colourless solution. A student carried out an experiment to investigate the effect of enzyme concentration on the rate at which trypsin hydrolyses casein. The student added a solution of trypsin to a sample of milk and recorded the time taken for the milk to become transparent. The student repeated the experiment with different concentrations of trypsin. All other variables were kept constant. Fig. 5.1 shows the results from the experiment. When the concentration of trypsin increases from $$$2.0 \%$$$ to $$$4.0 \%$$$, the time taken for the milk to become transparent decreases by $$$48 \%$$$. Calculate the percentage decrease in the time taken for milk to become transparent when the concentration of trypsin increases from $$$0.25 \%$$$ to $$$0.5 \%$$$. Write your answer to the nearest whole number. percentage decrease ..................................................... (ii) Explain the results shown in Fig. 5.1. ....................................................................................................................................... . ....................................................................................................................................... . ....................................................................................................................................... . ....................................................................................................................................... . ....................................................................................................................................... . ....................................................................................................................................... . ....................................................................................................................................... . ....................................................................................................................................... . ....................................................................................................................................... . ....................................................................................................................................... . ....................................................................................................................................... . ................................................................................................................................. Fig. 5.1

Biology

IGCSE&ALevel

CAIE

Exam No：9700_w24_qp_21 Year：2024 Question No：5(a)

Answer:

Knowledge points:

3.1.1 state that enzymes are globular proteins that catalyse reactions inside cells (intracellular enzymes) or are secreted to catalyse reactions outside cells (extracellular enzymes)

3.1.2 explain the mode of action of enzymes in terms of an active site, enzyme–substrate complex, lowering of activation energy and enzyme specificity, including the lock-and-key hypothesis and the induced-fit hypothesis

3.1.3 investigate the progress of enzyme-catalysed reactions by measuring rates of formation of products using catalase and rates of disappearance of substrate using amylase

3.1.4 outline the use of a colorimeter for measuring the progress of enzyme-catalysed reactions that involve colour changes

Answer:

Knowledge points:

Solution:

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