Enzymes in biotechnology: washing powder, pectinase and lactase sim

What the sim shows

Enzymes in biotechnology: three tests in one thermostatic water bath. Washing powder: a 3 cm × 3 cm cotton square with a dried egg stain goes into 50 cm³ of solution made with 0.5 g of biological or non-biological washing powder; time how long the stain takes to go, up to 30 minutes, and work out the rate (rate = 1000 / time). Fruit juice: 50 g of apple pulp with 2 cm³ of pectinase solution, or 2 cm³ of water as the control, stands 15 minutes in the bath and is then filtered for 10 minutes; read the volume of juice in the measuring cylinder. Lactose-free milk: 10 cm³ of milk with 1 cm³ of lactase solution, or water as the control, stands 10 minutes; dip a glucose test strip and match its colour with the chart. Set the bath with its dial, choose with or without the enzyme, press Fresh set-up, then drag the cloth into the beaker or drag the tube to pour it in. Only the wait buttons move time on. Biological powders contain proteases, which digest proteins such as egg into amino acids, and lipases, which digest fats into fatty acids and glycerol: the small products dissolve and wash out, and the powder works at low temperatures, which saves energy. Pectinase breaks down pectin, which holds plant cell walls together, so more juice is released and it is clearer. Lactase breaks down lactose into glucose and galactose, so lactose-intolerant people can drink the milk; the strip shows glucose, and Benedict's solution cannot be used, because lactose is a reducing sugar too. Each enzyme works faster when warmer, up to its optimum; above it, more and more of it is denatured (its active site changes shape for good), so the result falls. Simplified on purpose: the times, volumes and glucose values are illustrative (≈): real results depend on the powder, the enzyme, the fruit and the milk, and real values differ; each condition is run once, with no repeats and no random spread, so the same run always gives the same result; in a real class you would repeat each one and take a mean; the three enzymes follow one simple rule with their own constants: each works 1.8 times faster for every 10 °C warmer, and above its onset temperature (40 °C for the protease and lactase, 50 °C for pectinase) it is denatured, faster and faster the hotter it is; real enzymes differ; every set-up is already at the bath's temperature when it starts, and the bath holds every temperature exactly; a real bath takes time to settle; the stain is gone (the end-point) when the model's stain left reaches zero, and the stopwatch stops at that exact moment, even inside a 2 minute wait; the detergent alone lifts a little of the egg stain, more when hot, but never all of it in 30 minutes; the juice drips for exactly 10 minutes, the enzyme stops working once the pulp is in the funnel, and the juice's cloudiness is drawn from the pectin left, not measured; the glucose strip is read once, at 10 minutes (a real strip's pad is read a set number of seconds after dipping, as its tub says), and its colours follow a common type of strip (blue-green for none, to brown for a lot); always use the chart on your own strip tub; the bench apparatus is drawn to scale, and the close-up is not to scale.

• Lit: the bath's set-point dial
• Close-up: the reading for the test in hand (the stain and stopwatch, the cylinder's scale, or the strip and its chart)
• Dashed ring: where the carried cloth or tube goes

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