What enzymes are
What enzymes are
- A catalyst speeds up a reaction but is not used up.
- Enzymes are biological catalysts — and they are proteins.
- They control almost every reaction in a living thing.
Practice
An enzyme is:
Enzymes are protein catalysts: they speed up reactions and are not used up.
How an enzyme works
- Each enzyme has a pocket called the active site; the molecule it works on is the substrate.
- The active site shape is complementary to the substrate — they fit like a key in a lock.
- The substrate fits in, reacts, and the products leave — freeing the site to be used again.
Practice
The active site of an enzyme:
Only a substrate with the matching shape fits the active site — the lock-and-key idea.
Specific
- Each enzyme is specific — it works on only one kind of substrate.
- A different-shaped substrate won't fit, just as the wrong key won't open a lock.
Practice
Each enzyme is "specific" because:
A differently shaped substrate will not fit, so each enzyme works on just one substrate.
You've got it
Key idea
- an enzyme is a protein and a biological catalyst (speeds a reaction, not used up)
- the active site is complementary to the substrate (lock and key); products then leave
- each enzyme is specific to one substrate