The Signaling Pathway

In a typical signaling pathway, proteins are continually being modified and demodified. Kinases and phosphatases work ceaselessly like ants in a nest, adding phosphate groups to proteins and removing them again. It seems a pointless exercise, especially when you consider that each cycle of addition and removal costs the cell one molecule of ATP—one unit of precious energy. Indeed, cyclic reactions of this kind were initially labeled “futile.” But the adjective is misleading. The additio...

 Famous Tree Poem

I think that I shall never see A poem as lovely as a tree. A tree whose hungry mouth is prest Against the earth's sweet flowing breast; A tree that looks at God all day, And lifts her leafy arms to pray; A tree that may in Summer wear A nest of robins in her hair; Upon whose bosom snow has lain; Who intimately lives with rain. Poems are made by fools like me, But only God can make a tree.

 The Story of Flo, an Aging Chimpanzee Mother

Flo, inevitably, began to show her age. She wasn't strong enough to wean Flint when the time came, nor to care for her new infant Flame, born when Flint was only four and a half years old (the normal birth interval is five years or more). Flame disappeared during a time when Flo was too ill even to climb into a nest. Though she recovered somewhat after Flame's death, she did not have the strength to discipline Flint, who insisted on riding on her back and sleeping in her nest. When Flo died i...

 If Birds Studied Man

Let us only imagine that birds had studied their own development and that it was they in turn who investigated the structure of the adult mammal and of man. Wouldn't their physiological textbooks teach the following? 'Those four and two-legged animals bear many resemblances to embryos, for their cranial bones are separated, and they have no beak, just as we do in the first live or six days of incubation; their extremities are all very much alike, as ours are for about the same period; there i...

 Inter-Species Competition

A gazelle on the African savanna is trying not to be eaten by cheetahs, but it is also trying to outrun other gazelles when a cheetah attacks. What matters to the gazelle is being faster than other gazelles, not being faster than cheetahs. (There is an old story of a philosopher who runs when a bear charges him and his friend. "It's no good, you'll never outrun a bear," says the logical friend. "I don't have to." replies the philosopher. "I only have to outrun you.") In the same way, psycholo...