Page 168 - The Cell in 40 Topics

The Cell in 40 Topics

cate. Although they have never seen one another, they know which lan-
guage the other understands. In addition, this communication is for a pur-
pose. Two cells have joined forces and make plans for the food you’ve
eaten to be digested. There can be no doubt but that this is a great miracle.
The pancreas that receives the hormone cholesystokinin that reaches
it loses no time in obeying the instruction it conveys. Immediately the
gland begins secreting the enzymes necessary to digest that specific food. If
the meal is mainly carbohydrates it will produce an enzyme that breaks
down carbohydrate and sends this enzyme off to the duodenum.
Imagine that a blackboard has been placed in front of you containing
the formulae for a protein molecule, a fat molecule and a carbohydrate mol-
ecule, in that order. The atomic sequences of these molecules have also
been set out. You are then asked to produce the formulas for enzymes with
the molecular structure most appropriate for breaking down these differ-
ent molecules and to write them down on the board (Figure 135).
Only an expert chemist could write down the formulae for the en-

zymes that would break down these exact molecules. That person could
not arrive at the appropriate three formulas by guesswork; he could write
them correctly only in light of the training he had received and knowledge
previously imparted to him.

Figure 134.
The stomach sends
a message to the
pancreas by means
of hormones,
which find their
way through the
body in a miracu-
lous way and reach
the right location.

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