Enzyme Activity: Digestive Enzymes and Rate of Reaction Game

How to play Enzyme Activity

Enzyme Activity is a free GCSE biology game about enzyme activity and the enzymes that digest your food. A round has ten questions in three steps. First, you match amylase, protease and lipase to the molecules they break down and the products they make. Some questions ask about the lock and key model.

Next, you read a graph of the rate of reaction against temperature or pH. You pick the value where the rate is highest, or say why the rate falls past the peak. In the last step, you work out a rate from the time the starch took to disappear, as in the amylase practical.

You have 15 seconds per question to earn a bonus. A right answer scores 10, and 5 more if you beat the clock. On a keyboard, keys 1 to 4 pick an answer and Enter moves on. Harder start skips the matching step, so the graphs and rates come sooner. Turn on practice mode to play with no clock.

The science behind enzyme activity

Enzymes are biological catalysts. A catalyst speeds up a reaction and is not used up. Each enzyme has an active site, which is a part with a particular shape. Only one kind of molecule fits it, and we call that molecule the substrate. So each enzyme catalyses one reaction. The lock and key model shows this: the substrate fits the active site like a key fits a lock. AQA calls it a simplified model.

Digestive enzymes break large food molecules into small soluble ones that can pass into the blood. Amylase breaks down starch into sugars. Proteases break down proteins into amino acids. Lipases break down lipids, which are fats, into glycerol and fatty acids. The body then uses these small molecules to build new carbohydrates, lipids and proteins.

Temperature and pH change how fast an enzyme works. The optimum is the temperature or pH at which it works fastest. If it gets too hot, or the pH moves too far from the optimum, the active site changes shape. The substrate no longer fits, and we say the enzyme is denatured. OCR points out a common mistake: many students think every enzyme works best at 37 °C, body temperature. In fact, the optimum differs from one enzyme to another. Edexcel and OCR also ask how substrate concentration affects the rate, which this game does not test.

In the AQA practical, you mix amylase with starch solution at a range of pH values. A water bath or electric heater keeps the temperature steady. Every 30 seconds, you test a drop of the mixture with iodine. When the test shows no starch, you note the time. A shorter time means a faster rate, so rate = 1 ÷ time. Some questions use 1000 ÷ time instead, so always use the formula the question gives you.

This topic is AQA 8461 and 8464 section 4.2.2.1. The pH practical is required practical 5 in AQA Biology and required practical 4 in AQA Combined Science. Edexcel 1BI0 and 1SC0 cover enzymes in 1.7 to 1.12, with core practical 1.10. OCR J247 has them in B1.2f and B1.2g.

Tips for enzyme questions

• Protease and protein both start with prot. Lipase and lipid both start with lip.
• Starch, protein and lipids are the large molecules at the start. The products are the small molecules at the end.
• The optimum is the top of the curve. Read straight down from the highest point to the axis.
• Enzymes are proteins, not living things. When heat changes their shape, they are denatured, not killed.
• A longer time means a slower rate. Check that a longer time gives you a smaller number.
• A rate is per second. An answer in seconds is a time, so it cannot be the rate.

Use this enzyme game in the classroom

Enzyme Activity suits Years 9 to 11 when you teach digestion or revise enzymes before a test.

Use the rate step with the amylase and pH practical. Students can put their own times into rate = 1 ÷ time, then check their method against the game. The wrong options show real slips, such as giving the time in seconds as the rate, or turning the formula upside down.

Put a temperature graph on the board and ask why the rate falls past the peak. The game includes the wrong option that the enzyme has died. That gives you a way in to the difference between a living cell and a protein that has lost its shape. Then ask students to sketch the curve for an enzyme with a lower optimum and compare it with a partner.

With practice mode on, there is no clock. Students play without an account or a sign in. For more help with lessons, see our teachers page.

Enzyme questions

Teachers and students often ask us these questions about enzymes.