Page 146 - Design in Nature

144 DESIGN IN NATURE

The Ideal Shape of Red Blood Cells
Red blood cells have the responsibility of
carrying oxygen in the blood. Oxygen is carried in
the blood by haemoglobin which is stored in the red
blood cells. The larger the surface of this cell, the more
Red Blood Cells
oxygen is carried. Since red blood cells have to travel inside

capillaries, their volume has to be minimal i.e. they have to have the
maximum surface with minimum volume. Hence, red blood cells are
specially designed to fit these criteria: they are structured as flat, round and
pressed in on both sides, and resemble a wheel of Swiss cheese that is
squeezed on both sides. This is the shape that has the largest surface
possible with the smallest volume. Each red cell can carry 300 million
haemoglobin molecules due to this shape. In addition, red cells can pass

through the narrowest capillaries and tightest pores because of their
flexibility. 47

The Chromatic Eyes of Balloon Fish
Balloon fish reside in the warm seawaters of South-eastern Asia. When
excess amounts of light fall on them, the eyes
of this fish act as a “chemical sun-
glasses”. The eyes of this 1 inch long
(2.5 centimetre) fish show
properties similar to
photochromic lenses, the
colours of which can become
more or less intense
depending on the strength
of the light.
The system functions as
follows: when the fish
encounters excessive light, the
chromatic cells called
“chromatophore”, which are
located around the transparent layer