Lesson 1 ·Class 9 · Digestive System · Sort Lab
Enzymes and Their Properties
The rules every enzyme obeys.
Which statements are true of enzymes, and which are the common misconceptions?
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The heat-versus-cold distinction is the one most often got wrong: cold pauses an enzyme, heat destroys it.
What this lesson covers
Challenges to clear
- Sort every statement.
- Fill the 'Not true' box — every statement about enzymes that is a myth.
The task
Which statements are true of enzymes, and which are the common misconceptions?
What this lesson covers
- True of enzymes: They are proteins (Which is why heat destroys them — the protein is denatured.); Each enzyme acts on one substrate only (The lock-and-key fit — amylase will not touch protein.); They are not used up in the reaction (A catalyst emerges unchanged and can act again and again.); Each works best at a particular pH (Pepsin needs acid; pancreatic enzymes need an alkaline medium.); They work fastest around body temperature (Around 37 °C in humans; above about 45 °C they are destroyed.); A very small quantity affects a large amount of substrate (Because each molecule is reused many times over.)
- Not true: They are consumed and must be replaced after each reaction (That is what makes them catalysts rather than reactants.); One enzyme can digest any kind of food (Specificity is their defining property.); Freezing destroys them permanently (Cold only inactivates them. They recover on warming — unlike heat, which denatures them for good.); They can make a reaction happen that would otherwise never occur (An enzyme only speeds up a reaction that is already possible. It cannot force an impossible one.)
Hint
The heat-versus-cold distinction is the one most often got wrong: cold pauses an enzyme, heat destroys it.