Momo

5/23/11

History

If you wish to consider a profound question, ponder this: What change in all of history has made the greatest impression on postmodern society?

It seems, at first glance, a question as broad as time itself, especially when one examines the world today. To reach an answer, we must not travel forwards in time, but backwards.

For example, gaze upon a suburban street in postmodern America. The first highlight you notice that defines our era is probably the stream of different automobiles, varying from silver to red, busily gliding across the asphalt road. These curious machines are not only a radical form of transportation, but they come in a spectrum of colors, shapes, and sizes. This convenient form of travel is the result of mass production.

Mass production—it certainly made a great dent in society. Did this affect our world more than anything else? The answer is no, because an earlier change had to precede this one to light the fire of today’s society. That earlier change is, in fact, earlier than one might assume—strangely enough, mass production began in the Renaissance.

Now imagine the Renaissance, the great rebirth of Western society and culture. Imagine a scene in the northern Renaissance, in Maiz, Germany during the 15^th century—a printing press. A man in ink-stained clothes pulls a large handle over and over again. This seems to press a metal block upon a wooden table. Then the block is lifted away to reveal crisp, black text on a large sheet of paper made out of wood grain. This page is a part of the Bible. It is not an ordinary bible, though. It is not printed in Latin or Greek, but in German, the plain language of the common people! These common languages were called vernacular languages, and they practically did not exist in books until the Renaissance. This page that was printed in German is the 156^th page of the third copy of the Bible that was being copied at this printing press. This progress has been made in two days’ work only.

Travel even further back in time now, and imagine the Middle Ages in England. An enormous, silent cathedral is filled with monks. One holds a feather quill and runs its chiseled edge across a precious piece of paper. In about six seconds, a beautiful letter f is written. This monk is working on the Bible as well. The ink he skillfully tracks on the paper is made from ashes and egg, and the parchment he will use to complete his entire book required three hundred sheepskins to make. No wonder he takes such care in forming his letters on the thin paper. This Bible will be valuable and prized, for it will take months to make. It is being written in Latin, and only priests and other holy people will be able to read it.

Pick up these three scenes of postmodern America, Renaissance Germany, and the Middle Ages in England. Place these three scenes next to each other. Which one is the odd one out? Which two have some key thing in common that one does not? Look again. What do postmodern automobiles and Renaissance printed books have that Medieval manuscripts do not?

Imagine your life in postmodern America. Imagine that vernacular languages, printing, and mass production did not exist. You would not be able to read unless you knew Latin. You probably could not afford books and would rely on a priest to interpret the Bible for you. One lamp in your house, one car or computer or desk or water glass would have been manufactured in your neighborhood, and would have required endless time and energy. You would not have very much of an education. Gathering information was impossible unless you listened to a lecture by a professor, and even then you did not know if the professor’s knowledge was legitimate. Your life could have easily been this way. But the first hint, the first inspiration of mass production is what changed our future. The printing press is what shaped the world into what it is today.

Within the Leaves

Momo

The “reason why plants are green” is generally considered a simple subject to be taught to grade school students. Many people are aware that what makes plants green is a substance called chlorophyll. But the chlorophyll is not the reason why plants are green, just what makes them that color. The true question is, Why green? Why not purple or red?

The answer simmers down to the nature of photosynthetic plants. Almost all plants are photosynthetic autotrophs. This means that they create their own food energy from inorganic material using the process of photosynthesis.

Photosynthesis requires water as an inorganic ingredient, and happens within a plant’s leaves. Leaves contain cells like all matter of living organisms, and these cells contain various organelles including chloroplasts. Many chemical reactions of photosynthesis occur within the membrane of a chloroplast, which encloses a compartment filled with stoma, a fluid containing enzymes and sacks called thylakoids. Thylakoids form in stacks called grana. Chlorophyll molecules which capture light energy reside in the thylakoid membranes.

Diving deep into the chemical process of photosynthesis requires review of the basics—plants take in carbon dioxide and water, and light energy fuels a process which will result in a waste product, glucose and oxygen. Animals take in plants’ whaste products and plants take in animals’ waste products. This is a constant handshake between animals and plants that keeps both alive. Here is a more complex equation of the simplified photosynthesis:

We know the beginning ingredients and final byproducts, but the actual reaction is only simplified to an arrow. The chemical reaction does not just occur; it must go through several complex but quick reactions.

It begins with the electrons taking an uphill path, adding to carbon dioxide to form sugar. Hydrogen is moved too alongside the electrons, redox processes taking the form of hydrogen transfer from water to CO2, requiring chloroplasts to split water molecules (H20) into hydrogen and oxygen. Hydrogen is then transferred along with the electrons to the CO2 to form sugar. Oxygen escapes through pores in the plant’s leaves called stomata; this released oxygen is one of the waste products of photosynthesis.

This is a diagram of the process above:

The Calvin Cycle uses products of light reactions to power the production of sugar from C02. The enzymes for the Calvin Cycle are dissolved within the stoma. Light reactions convert solar energy to chemical energy, using light to drive the synthesis of ATP and NADPH, an electron carrier. Light drives electrons from NADP+, an oxidized form of this carrier, to form NADPH, a reduced form. The Calvin Cycle does not directly produce sugar; it powers sugar production which will happen later.

The light that fuels all of these processes is an entirely different subject, but the nature of light still must be understood to completely understand why plants appear green.

Sunlight is a form of electromagnetic energy. Electromagnetic energy travels through space in the form of rhythmic waves analogous to the waves produced by a pebble being dropped in a pond. The difference between the highest crests of a wave is called the wavelength. The full range of radiation’s wavelengths is called the electromagnetic spectrum.

Visible light is the light we can see, the light which reflects into our eyes and makes the world visible to us and which allows us to see colors. It is also the weakest type of light, making it harmless to living organisms’ eyes or bodies. This type of light claims only a small portion in the middle of the electromagnetic spectrum, and ranging from red to violet, all colors with different wavelengths, the wavelengths of visible light range from 380nm to 750 nm.

Sunlight shines on a pigmented material, and most of the light is instantly absorbed by it. The wavelength which is reflected by the material is the color of light which we see.

Of course, light is absorbed by plants to fuel photosynthesis. Now that we have learned how each color of visible light has a different wavelength, we can understand that different wavelengths of light promote the process of photosynthesis more effectively than others. There are two types of chlorophyll, chlorophyll a and chlorophyll b. The wavelengths of indigo and red-colored light are absorbed best by chlorophyll a, and blue and orange by chlorophyll b. Chlorophyll b does not directly take part in processing light reactions, but broadens the range of light a plant can use, conveying absorbed energy to chlorophyll a and thus making photosynthesis into a more efficient process.

Chloroplasts also contain carotenoids, which absorb blue-green light, some passing energy to chlorophyll a, some having a protective function: they absorb and put aside excess light which would otherwise cause damage to the chlorophyll. Fall colors appear when chlorophyll decreases, revealing the colors reflected by the carotenoids.

Carotenoids reflect warm colors into our eyes during the fall because they absorb blue-green light and reflect the opposite—red and orange. Chlorophyll does the same. Wavelengths of red and indigo are absorbed, but the opposite, green and yellow light, is reflected. This is why plants appear green to out eyes!

Light has other behaviors other than rhythmic waves. It can assume the nature of a photon, a small, fixed quantity of light energy. The wavelength of purple photons has almost twice as much energy as red.

When a pigment molecule absorbs a photon, one of its electrons gains energy, leaping into an unstable and excited state. It is unstable enough that it usually falls back instantly to its ground state. The fall of the electron produces energy. Most pigments will release heat when its electrons fall to their ground state, which is why the color black will absorb more heat than white in the sun.

Some pigments produce light energy as well. When you break a glow stick, two chemicals combine, exciting the chemical with a fluorescent dye. Excess energy is emitted as light.

Here is a diagram of a pigment absorbing a photon:

Chlorophyll is organized with other molecules into photosystems. Each photosystem is comprised of a few hundred pigment molecules including chlorophyll a and b along with carotenoids. The cluster of pigment molecules acts as a light-attracting antenna. When a photon strikes a pigment, the energy jumps from molecule to molecule until it reaches the reaction center, which consists of a chlorophyll a molecule next to a primary electron acceptor. It traps the excited electron, producing ATP and NADPH.

There are three types of processes within the photosystems: water-splitting, NADPH-producing, and the final stage. In the first, photons excite electrons in the chlorophyll of the water-splitting photosystem. It is them trapped by the electron acceptor. The photosystem extracts electrons from water, releasing O2.

In the second photosystem, energized electrons from water-splitting photosystems pass down an electron transport chain to the NADPH-producing photosystem.

In the third photosystem, the NADPH-producing photosystem transfers light-excited electrons to NADP+, reducing it to NADPH.

Photosynthesis is a process that can either be explained simply or completely. All of the previous information did not even tell the complete story of this complex process. And in the future, we will only break the process down further, and we will only discover more.

© 2011, Momo