Pectinase, biological washing powders and lactaseSpec 21.2.3, 21.2.4, 21.2.5
Pectinase in fruit juice production
Plant cell walls contain pectin, which helps to hold the cells together. The enzyme pectinase breaks down pectin. It is added to crushed fruit pulp before pressing. This breaks down the cell walls, so more juice is released (a higher yield). Pectinase also makes the juice clearer, because less pectin is left in the juice.
Biological washing powders
Biological washing powders contain enzymes that digest stains. Proteases break down protein stains (such as blood or egg) into amino acids. Lipases break down fat and grease stains into fatty acids and glycerol. Amylases break down starch stains into sugars. The products are small, soluble molecules, so they wash out of the clothes.
Biological powders clean well at low temperatures, such as 30 to 40 °C, so less energy is used to heat the water. If the water is too hot, the enzymes are denatured and the powder removes stains no better than a non-biological powder.
Investigating a biological washing powder
- Stain identical squares of the same cloth with the same volume of the same stain, such as egg white, and leave them to dry for the same time.
- Make up the same volume and concentration of biological washing powder solution in several beakers, and put each in a water bath at a different temperature (for example 20, 30, 40, 50 and 60 °C).
- When each solution has reached its temperature, add one cloth and stir in the same way.
- Record the time taken for the stain to disappear. (Alternatively, wash every cloth for the same time and compare how much stain is left.)
- Repeat at each temperature and calculate a mean. Set up controls: the same stain washed in water only, and in biological powder solution that has been boiled and cooled (so its enzymes are denatured).
Independent variable: temperature (or pH, or type of powder). Dependent variable: time for the stain to disappear. Keep the same: cloth, stain, volume and concentration of solution, stirring and pH. Typical result: the stain is removed fastest at about 40 °C, more slowly at lower temperatures, and slowly or not at all at high temperatures, where the enzymes are denatured. Enzyme powders can cause allergies and irritate skin and eyes, so avoid contact and wear eye protection.
Supplement (what this means)
Supplement: only for the Extended papers (2 and 4). Core students can skip it. What the labels meanLactase and lactose-free milk
Supplement (what this means)
Supplement: only for the Extended papers (2 and 4). Core students can skip it. What the labels meanMilk contains the sugar lactose. Some people are lactose intolerant: they cannot digest lactose properly. The enzyme lactase breaks down lactose into the simpler sugars glucose and galactose, which are easily absorbed. Adding lactase to milk produces lactose-free milk, which lactose-intolerant people can drink.
Supplement (what this means)
Supplement: only for the Extended papers (2 and 4). Core students can skip it. What the labels meanName the substrate and both products when explaining lactase: lactose is broken down into glucose and galactose.