Enzyme Activity Virtual Lab: Temperature and pH

Updated 2026-10-06

This enzyme activity virtual lab follows the AP Biology enzyme investigation and the AQA GCSE required practical on pH and amylase. Students change one factor at a time, record the relative rate of salivary amylase, and plot it against temperature and pH. Then they heat the enzyme past its optimum and cool it again. They come away with two graphs, an optimum for each factor, and a Q10 calculated from their own readings. Every number here was read from the simulation.

Enzyme activity vs. temperature, pH, substrate concentration and inhibitors

Curriculum links

AP Biology: Unit 3 (Cellular Energetics), topic 3.3, environmental impacts on enzyme function (ENE-1), and the AP enzyme activity investigation. The AP lab uses peroxidase or catalase; this simulation uses amylase, pepsin and trypsin, with the same variables and the same kind of result.
AQA GCSE Biology: specification 4.2.2.1, the required practical on the effect of pH on the rate of reaction of amylase. In the wet lab, students time when the iodine test stops turning blue-black. Here the simulation reports the rate directly.
Simulic is not affiliated with or endorsed by the College Board or AQA.

Before the lab (5 min)

Ask: "Amylase is kept at pH 7 while the temperature rises from 10 °C to 70 °C. How will its rate change?" Students choose a steady rise, a peak then a fall, a flat line or a steady fall, and write one reason. On a class link this is question 1; the simulation unlocks after they answer.

Method in the simulation

The line under the simulation shows the rate model, v = Vmax·f(T)·f(pH)·[S]/(Km + [S]). f(T) and f(pH) run from 0 (no activity) to 1 (fastest); students record them as the relative rate. The "measured" number counts products in the last 5 seconds and jumps around, so use it only to see whether the enzyme works at all.

In the starting values below the simulation, choose Salivary amylase and Inhibitor None. The simulation starts at 37 °C and pH 7.
Temperature series. Keep pH at 7. Drag the T slider to each temperature in the table and record f(T). Do 60 °C last.
At 60 °C, watch the enzymes turn grey and the status line show DENATURED.
Drag T back to 37 °C without pressing Reset. Watch the enzymes and the measured rate for 20 seconds. Then press Reset.
pH series. Keep T at 37 °C. Set each pH in the table and record f(pH).
Plot relative rate (f × 100) against temperature, and against pH.

Temperature (°C)	10	20	30	37	45	50	60
f(T)
Relative rate (%)

pH	3	5	6	7	8	9	11
f(pH)
Relative rate (%)

Expected results

Amylase at pH 7 gives f(T) = 0.15 at 10 °C, 0.31 at 20 °C, 0.62 at 30 °C, 1.00 at 37 °C, 0.80 at 45 °C, 0.48 at 50 °C and 0.00 at 55 °C and above. Below the optimum, each 10 °C rise doubles the rate: 0.50 at 27 °C becomes 1.00 at 37 °C. Above the optimum, the rate falls much faster than it rose.

At 37 °C, f(pH) is 0.00 at pH 3, 0.21 at pH 5, 0.68 at pH 6, 1.00 at pH 7, 0.68 at pH 8, 0.21 at pH 9 and 0.00 at pH 11. The curve is symmetrical around pH 7. Pepsin peaks at pH 2 and trypsin at pH 8, and each gives f(pH) = 0.00 at the other one's optimum.

After 60 °C and cooling back to 37 °C, the enzymes stay grey, the product-over-time line goes flat and the measured rate stays at 0 product / 5 s. Point out that the v line shows a value again (about 61): the formula describes a working enzyme, while the grey molecules show what happened to this batch.

Questions for students

Prediction: amylase is kept at pH 7 while the temperature rises from 10 °C to 70 °C. How will its rate change?
In the pH part of the lab, which variables must you keep the same?
Amylase at 37 °C, pH 5. What is f(pH)?
Read f(T) at 27 °C and at 37 °C (pH 7). Calculate Q10 = rate at 37 °C ÷ rate at 27 °C.
Heat amylase to 60 °C, then cool it to 37 °C without Reset. Describe and explain what you see.

Answers for teachers:

It rises to a peak near 37 °C, then falls to zero by 55 °C.
The temperature (37 °C) and the enzyme.
0.21 (accepted ± 0.02).
1.00 ÷ 0.50 = 2.0 (accepted ± 0.1).
The enzymes stay grey and no product forms. Heat changed the shape of the active site, the substrate no longer fits, and cooling does not reverse it.

Common misconceptions

"Heat kills the enzyme." Enzymes are molecules, not living things. They denature: they lose their shape.
"Cooling brings the activity back." Not after 55 °C: in this model only Reset restores it.
"Cold denatures enzymes too." At 10 °C the rate is low (0.15), but it rises again when warmed.
"Every enzyme works best at pH 7." Pepsin works best at pH 2, in the stomach.

Extension

Inhibitors (AP). In the starting values, compare Inhibitor None, Competitive and Non-competitive. At the start, v is 62.5, about 35 and 20.8. Press +20 substrate several times: extra substrate wins back much of the rate against a competitive inhibitor, but not a non-competitive one.
Three enzymes. Plot the pH curves of amylase, pepsin and trypsin on one graph and link each optimum to its place in the gut.

FAQ

Why record f(T) and f(pH) instead of counting products?

The product count comes from a few moving molecules, so it varies a lot from one 5-second window to the next. The factors give every student the same values at the same settings, so class graphs can be compared.

Does this replace the wet lab?

Not for AQA: required practicals must still be done by hand. Use the simulation to plan and predict, or to explain the results. See virtual labs vs physical labs.