Chloroplasts bear chlorophyll; they give the green world its color, and they carry out the business of photosynthesis. Around the inside perimeter of each gigantic cell trailed a continuous loop of these bright green dots. They spun . . . they pulsed, pressed, and thronged . . . they shone, they swarmed in ever-shifting files around and around the edge of the cell; they wandered, they charged, they milled, raced . . . they flowed and trooped greenly . . . All the green in the planted world consists of these whole, rounded chloroplasts . . . If you analyze a molecule of chlorophyll itself, what you get is one hundred thirty-six atoms of hydrogen, carbon, oxygen, and nitrogen arranged in an exact and complex relationship around a central ring. At the ring’s center is a single atom of magnesium. Now: If you remove the atom of magnesium and in its place put an atom of iron, you get a molecule of hemoglobin. The iron atom combines with all the other atoms to make red blood, the streaming red dots in the goldfish’s tail.

Mr. Leadbeater was then staying at my house, and his clairvoyant faculties were frequently exercised for the benefit of myself... I had discovered that these faculties, exercised in the appropriate direction, were ultra-microscopic in their power. It occurred to me once to ask Mr. Leadbeater if he thought he could actually see a molecule of physical matter. He was quite willing to try, and I suggested a molecule of gold as one which he might try to observe. He made the appropriate effort, and emerged from it saying the molecule in question was far too elaborate a structure to be described. It evidently consisted of an enormous number of some smaller atoms, quite too many to count; quite too complicated in their arrangement to be comprehended... I suggested an atom of hydrogen as possibly more manageable. Mr. Leadbeater accepted the suggestion and tried again. This time he found the atom of hydrogen to be far simpler than the other, so that the minor atoms constituting the hydrogen atom were countable. They were arranged on a definite plan, which will be rendered intelligible by diagrams later on, and were eighteen in number. (Chapter I. A Preliminary Survey)

I am, reluctantly, a self-confessed carbon chauvinist. Carbon is abundant in the Cosmos. It makes marvelously complex molecules, good for life. I am also a water chauvinist. Water makes an ideal solvent system for organic chemistry to work in and stays liquid over a wide range of temperatures. But sometimes I wonder. Could my fondness for materials have something to do with the fact that I am made chiefly of them? Are we carbon- and water-based because those materials were abundant on the Earth at the time of the origin of life? Could life elsewhere — on Mars, say — be built of different stuff? I am a collection of water, calcium and organic molecules called Carl Sagan. You are a collection of almost identical molecules with a different collective label. But is that all? Is there nothing in here but molecules? Some people find this idea somehow demeaning to human dignity. For myself, I find it elevating that our universe permits the evolution of molecular machines as intricate and subtle as we. But the essence of life is not so much the atoms and simple molecules that make us up as the way in which they are put together. Every now and then we read that the chemicals which constitute the human body cost ninety-seven cents or ten dollars or some such figure; it is a little depressing to find our bodies valued so little. However, these estimates are for human beings reduced to our simplest possible components. We are made mostly of water, which costs almost nothing; the carbon is costed in the form of coal; the calcium in our bones as chalk; the nitrogen in our proteins as air (cheap also); the iron in our blood as rusty nails. If we did not know better, we might be tempted to take all the atoms that make us up, mix them together in a big container and stir. We can do this as much as we want. But in the end all we have is a tedious mixture of atoms. How could we have expected anything else? Harold Morowitz has calculated what it would cost to put together the correct m

What takes place within the structure of the leaf, then, with the aid of the wonderful green workmen, is this: A certain number of molecules of water, brought to the leaf from root and stem, are taken in hand and compounded with a certain number of molecules of carbon extracted from the air that has been brought into the leaf laboratory through its mouths or ta from the outside atmosphere.
When the compound has been effected, we still have the atoms of hydrogen and oxygen that composed the water molecules and the atoms of carbon, but they are so marvelously put together that they no longer constitute the liquid water or the gas in which the carbon was imported. They now constitute an altogether new substance which is termed sugar.
Thus only three elements are dealt with and these very familiar ones. It would seem as if almost any chemist should be able to manage a simple combination like that. But... no human chemist knows how to manage it. There are forces to be invoked in effecting that combination of which no chemist has any knowledge.
Only the chlorophyll grains in the plant leaf have learned the secret, and up to the present they have kept their secret well.

I am a collection of water, calcium and organic molecules called Carl Sagan. You are a collection of almost identical molecules with a different collective label. But is that all? Is there nothing in here but molecules? Some people find this idea somehow demeaning to human dignity. For myself, I find it elevating that our universe permits the evolution of molecular machines as intricate and subtle as we.

But the essence of life is not so much the atoms and simple molecules that make us up as the way in which they are put together. Every now and then we read that the chemicals which constitute the human body cost ninety-seven cents or ten dollars or some such figure; it is a little depressing to find our bodies valued so little. However, these estimates are for human beings reduced to our simplest possible components. We are made mostly of water, which costs almost nothing; the carbon is costed in the form of coal; the calcium in our bones as chalk; the nitrogen in our proteins as air (cheap also); the iron in our blood as rusty nails. If we did not know better, we might be tempted to take all the atoms that make us up, mix them together in a big container and stir. We can do this as much as we want. But in the end all we have is a tedious mixture of atoms. How could we have expected anything else?

The chemistry of living organisms is organized around carbon, which accounts for more than half the dry weight of cells.

There are as many atoms in one molecule of DNA as there are stars in a typical galaxy.

Except for hydrogen, all the atoms that make each of us up — the iron in our blood, the calcium in our bones, the carbon in our brains — were manufactured in red giant stars thousands of light-years away in space and billions of years ago in time. We are, as I like to say, starstuff.

all the atoms that make each of us up — the iron in our blood, the calcium in our bones, the carbon in our brains — were manufactured in red giant stars thousands of light-years away in space and billions of years ago in time. We are, as I like to say, starstuff.

The neutrons, as we have said and as their name suggests, carry no electrical charge. The protons have a positive charge and the electrons an equal negative charge. The attraction between the unlike charges of electrons and protons is what holds the atom together. Since each atom is electrically neutral, the number of protons in the nucleus must exactly equal the number of electrons in the electron cloud. The chemistry of an atom depends only on the number of electrons, which equals the number of protons, and which is called the atomic number. Chemistry is simply numbers, an idea Pythagoras would have liked. If you are an atom with one proton, you are hydrogen; two, helium; three, lithium; four, beryllium; five, boron; six, carbon; seven, nitrogen; eight, oxygen; and so on, up to 92 protons, in which case your name is uranium.

I stand at the seashore, alone, and start to think.
There are the rushing waves
mountains of molecules
each stupidly minding its own business
trillions apart
yet forming white surf in unison.<p>Ages on ages
before any eyes could see
year after year
thunderously pounding the shore as now.
For whom, for what?
On a dead planet
with no life to entertain.<p>Never at rest
tortured by energy
wasted prodigiously by the sun
poured into space.
A mite makes the sea roar. <p>Deep in the sea
all molecules repeat
the patterns of one another
till complex new ones are formed.
They make others like themselves
and a new dance starts.<p>Growing in size and complexity
living things
masses of atoms
DNA, protein
dancing a pattern ever more intricate.<p>Out of the cradle
onto dry land
here it is
standing:
atoms with consciousness;
matter with curiosity.<p>Stands at the sea,
wonders at wondering: I
a universe of atoms
an atom in the universe.

became the study of how... simple molecules were interconnected one into another. ...The [simple] molecules ...containing ...up to about twenty carbons, but most ...have fewer than ten.

Human blood has a chemical composition startingly similar to seawater.

I know what the atom looks like!