Biological washing powders and liquids contain enzymes that help remove stains from clothes.

The enzymes break down substances that make the clothes dirty, speeding up the stain removal process.

Explain why biological washing powders do not work well if you wash your clothes with very hot water.

A company has formulated a new washing powder.

The washing powder is being advertised as the company's best laundry detergent for baby clothes.

Baby food is usually rich in starch.

Suggest which enzyme the company has added to their new washing powder.

Some parents might prefer to use non-biological detergents to wash their babies' clothes.

Suggest why.

Describe how you would plan an experiment to find the best temperature for removing stains from clothing.

Include the laboratory equipment you would use and how you would make the investigation a fair test.

Suggest a reason why some people think that biological washing powders are better for the environment than non-biological ones.

Some baby foods are treated with the enzyme trypsin, a type of protease.

Trypsin pre-digests the baby food, helping the babies digest the food until their stomachs are able to break down bigger protein molecules more easily.

Suggest the effect trypsin has on the baby food.

Name two other types of enzyme that break down food, along with their respective substrates.

List and describe two other uses of enzymes in different industries.

Enzymes are affected by changes in temperature.

The temperature at which the enzyme is most active is known as the optimum temperature.

What is an enzyme?

Fill in the missing words in the following sentences:

An enzyme works on the substrate, forming products.

Substrate molecules fit into the of the enzyme like a lock and . 

An enzyme’s active site and its substrate are in shape.

What are enzymes made of?

Suggest the optimum temperature for human enzymes.

Explain the effect of temperature on enzyme activity.

Amylase is an enzyme that catalyses the breakdown of starch into sugars.

Amylase is naturally found in the saliva of humans and some other mammals.

Explain how amylase breaks down starch. 

Answer in terms of the lock and key model of enzyme activity.

Describe how a student could investigate the effect of pH on the activity of amylase.

State the variables that the student would have to control during the investigation.

Describe how the student could extend the investigation to determine the effect of a different factor on amylase activity.

Stonewashed jeans are denim jeans that undergo a treatment process to achieve a faded and worn-out appearance.

There are two main methods used to achieve this effect:

1. Washing the jeans in a rotating drum with pumice stones and very hot water for up to five hours. This method will mechanically remove any dye by distressing the denim fabric.
2. Washing the jeans for half an hour in warm water in the presence of enzymes, depending on the dye used. Some of the enzymes used are expensive. Additionally, the enzymes need to be removed from the jeans after this treatment.

Suggest two advantages and two disadvantages of using enzymes instead of the traditional stonewashing method using pumice stones.

Cellulase is one of the enzymes that can be used to achieve stonewashed jeans.

The substrate of cellulase is cellulose, a carbohydrate.

What type of enzyme is cellulase?

Some blue dyes are made of protein.

Using your knowledge of enzymes, suggest which type of enzyme you might expect to use to remove those dyes from fabrics.

Milk can be made to last longer by using two different methods.

1. Using hydrogen peroxide

By introducing a small quantity of hydrogen peroxide to the milk, the bacteria responsible for milk decay can be killed, although not all disease-causing bacteria are affected.

To remove the hydrogen peroxide, the enzyme catalase is added to the treated milk.

Catalase breaks down hydrogen peroxide into oxygen and water.

1. Pasteurisation

Heating the milk to a high temperature for a specific duration eliminates harmful bacteria.

Suggest one advantage and one disadvantage of using hydrogen peroxide and catalase to preserve milk instead of pasteurisation.

Milk fat is a type of lipid. What is the name of the enzyme that catalyses the breakdown of lipids and fats?

What are the products of the breakdown of lipids and fats?

What do you predict will happen to the pH of milk if the milk fat is broken down by an enzyme? Explain your answer.