On Food and Cooking

water and other small molecules. Immediately
inside the membrane is a fluid called the
cytoplasm, which is filled with much of the
complex chemical machinery necessary to the
cell’s growth and function. Then within the
cytoplasm float a variety of other membrane-
contained bags, each with its own chemical
nature. Nearly all plant cells contain a large
watery vacuole, which may be filled with
enzymes, sugars, acids, proteins, water-
soluble pigments, and waste or defensive
compounds. Often one large vacuole will fill
90% of the cell volume and squeeze the
cytoplasm and nucleus (the body that contains
most of the cell’s DNA) up against the cell
membrane. Leaf cells contain dozens to
hundreds of chloroplasts, bags filled with
green chlorophyll and other molecules that do
the work of photosynthesis. The cells of fruits
often contain chromoplasts, which concentrate
yellow, orange, and red pigments that are
soluble in fat. And storage cells are often