21. What is the relationship
between vitamins and enzyme
cofactors?

Gap-fill exercise

Fill in all the gaps, then press "Check" to check your answers. Use the "Hint" button to get a free letter if an answer is giving you trouble. You can also click on the "[?]" button to get a clue. Note that you will lose points if you ask for hints or clues!
Many are enzyme cofactors
that cannot be by the
organism and must be obtained from
the .