Proteins

1. Protein produced by living cells which act as a biological catalyst which speeds up chemical reactions
5. A protein that is involved in defence in animals
7. Fitting together like a hand in a glove
8. The position on the surface of an enzyme molecule to which specific substrate molecules can bind
10. The substance made by an enzyme-catalysed reaction
11. A reaction that breaks large molecules into smaller ones
12. The shape of the active site is complementary to this

2. Each different enzyme acts on only one substrate
3. Cell surface protein which allows a cell to recognise specific substrates
4. Protein released by an endocrine gland into the blood to act as a chemical messenger
6. Examples include proteins in membranes, muscle, bone and nails
9. A reaction that builds smaller molecules into larger ones