Cytochromes and Mitochondria

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SPECTROSCOPIC VIEWS OF PHOTOSYNTHESIS

..... In the early days of biochemistry, when there were no "properly" trained biochemists, all advances were made by workers scattered all throughout the sciences. Thus it might be appropriate to subtitle this exercise as:

The Discovery of Helium on the Sun, the Order of Cytochrome Utilization, AND How the Light Reaction Works in Photosynthesis

This is because physicists played an important role in opening this important door into the land of biochemistry and the transport of electrons from NADH to oxygen gas to make water, and, ironically, from water to make oxygen.

..... It had long been known that prisms "break up" white light into the rainbow of colors. ..Then it was found that when using the sun's light there were a multitude of very thin black lines seemingly spaced randomly upon the rainbow. ..These were soon shown to be "absorption lines" caused by intervening gases, most of which were not the atmosphere of the earth, but rather the much more abundant gases in the solar atmosphere. ..It was known then that each gas would cause very specific lines to form, and that all the lines but a few could be accounted for by the known elements. ..What was the nature of the gas that absorbed the wavelengths causing those few previously unseen mysterious lines? ..Physicists quickly determined that atoms of the unknown element consisted of two protons and probably two neutrons and attendant electrons. ..Since this element was first detected on the sun (Greek: helios), it was named helium.

..... So what does this have to do with chlorophyll biochemistry? ..One of the wonderful things about this technique is that is non-destructive: one can look at living leaves without demolishing them. .. Let's speculate on a few things that we might very easily determine:

The number of different pigments in the leaf. .. (Each pigment will absorb a different part of the spectrum, so each dimmed area in the spectrum indicates at least one pigment.)
The biophysical mechanism of photosynthesis... (Since each color in the spectrum has a specific energy level, we might hope to figure out just how much energy the leaf takes in, and whether it is enough, theoretically, to rip electrons off water's oxygen to yield oxygen gas.)

..... While this is not a biophysics course, let's at least have a little fun with rainbows and colors! ..We can get a glimpse of some things most of us have never seen before with our own eyes.

..... In general you will need:
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A spectroscope or some sort of spectrophotometer
(the former is highly preferable and if used will cut the length of the exercise greatly)
A collection of different leaves - perhaps of different colors
A fluorescent light
The sun (even a cloudy day works)
A bright incandescent light source

The SPECTROSCOPE. ..This is something that many chemistry and physics labs have locked away. ..Once you have one, FIRST ask for instructions on how to use it. ..Once you have learned how to use it, have a little fun and scout out the world around you. .. Here is a short list of things to look at:
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FIRST! ..Look at the fluorescent lights overhead. ..They are very handy for helping you get into proper focus: ..focus on the mercury vapor emission lines, which are brightly superimposed on a background rainbow. .. DO NOT TOUCH THE FOCUS HEREAFTER!
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Look at the sky during the day. .. Even on cloudy days! ..All the light you will "scope" will be that of the sun - even if diffused through clouds. ..Do you see dozens of very thin dark lines? ..Those are the solar absorption lines mentioned earlier.
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Your incandescent light source (you should see a smooth rainbow with neither bright or dark lines superimposed on it).
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Look around for any neon, argon or xenon lamps. ..These are usually very small on/off indicator lights on some items of equipment. ..Hold the spectroscope right up to the light and take a peek at the emission lines.
..
Obtain a Meeker burner, which is a Bunsen burner with a little grill on top, which breaks up the Bunsen's one flame into dozens of closely packed little flames. ..One at a time place on the grill chuncks of various salts your chemistry teacher can give you. ..Light the burner and "scope" the colors. .. Now you see several different sets of emission lines.

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LEAVES ..Go out and collect a variety of leaves. ..Fall colors offer a very good experience!

A bright INCANDESCENT LIGHT is required. ..A good one might be simple a 100 W bulb in a lamp fixture. ..To help shield your eyes, between you and the lamp set up a large piece of cardboard that has an appropriately placed 1 cm diameter hole in it. ..Put your leaves up to the hole when looking at them. ..Rapidly alternate between looking at the leaf and directly at the light source. ..This will help you see which portions of the spectrum are being absorbed by the leaf. Do this with several different leaves, and compare your observations with of your partner.
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