**3.2 Case 2: A role for zinc in cell fertilization, differentiation, lactation**

#### **3.2.1 A historical perspective on the cell biology of zinc**

Zinc has long been known to play an important role in biology. Studies of the biochemistry of zinc may well have first begun in the 1950's, with the study of metallothionein. We now know that zinc plays both structural roles, such as in zinc finger proteins, and catalytic roles such as it does in carbonic anhydrase. Yet, there remains much to learn about this metal. Results from direct X-ray fluorescence imaging of this element in cells may indeed have revealed that there is still much to learn.
