Excerpts from Photosynthesis Literature Review Sections

Good Excerpts

Note that while none of these quotes would stand alone as a good Literature Review, a number of these ideas combined together might do quite nicely.

♦ Photosynthesis is simply the manufacture of organic material from water and carbon dioxide by green plants in the light (Roberts and Whitehouse, 1976). Photosynthesis occurs in small organelles of a plant called chloroplasts. These organelles contain pigments which absorb light energy. There are at least eight different kinds of pigments (Foyer, 1984), but the three major ones include chlorophyll A, chlorophyll B, and the carotenoids (Roberts and Whitehouse, 1976). Each pigment absorbs light, however chlorophyll A is the main source for absorption.

♦ Plants can use sunlight as an energy source for carbon fixation (Ellemore and Smith, 1983). However, different wavelengths are not equally effective in promoting photosynthesis. Generally plants reflect green light having wavelengths of approximately 550 nm. This wavelength would not be expected to produce much carbon fixation. Thus, the measurement of photosynthesis in plants can be made by monitoring gas exchange.

♦ (While this could be fleshed out some, this is a good start at relating the literature findings to the current experiment. Note the use of “(author, year)” to cite references.)

♦ The leaves of plants are green due to the reflection of green light. Green light has a wavelength of approximately 515 to 550 nm. Chlorophyll is the pigment that reflects green light, and is the most important pigment used in photosynthesis. Chlorophyll captures light in the violet, red, and blue portions of the electromagnetic spectrum (Crosby, 1997). There are two types of chlorophyll. Chlorophyll A is found in different forms in the photosystems (Holt, 1991), and is a blue-green pigment which will absorb the most light at approximately 430 nm, and also at 660 to 700 nm. Chlorophyll B, a yellow-green pigment, absorbs the most light at around 450 and around 650 nm. Carotenoids are shades of yellow and orange, and along with other accessory pigments, absorb wavelengths of light that chlorophyll cannot (Crosby, 1997). This broadens the spectrum of light energy that can be fixed through photosynthesis.

♦ “Photosynthesis is the metabolic process by which solar energy is trapped and stored in the bonds of organic nutrient molecules such as glucose and other carbohydrates” (Postlethwait and Hopson, 1976).

♦ The first step in photosynthesis is the absorption of light by pigments (Crosby and Raven, 1996).

♦ Use 6 CO2 + 12 H2O → C6H12O6 + 6 O2 — Use an arrow in chemical reactions, and do it on your computer. In WordPerfect, do [ctrl]-w, then 6,21 to get an arrow. I have been told that in Word, the combination ==> should self-correct to an arrow. Better yet, learn how to use the equation editor. Learn how to use your word processing program like a scientist. If you’re working in HTML, things are a bit more difficult because there is no right arrow in the regular character set, but the combination “→” will produce an arrow. Optionally, you could use the equation editor in WordPerfect or Word to produce the desired text, then save that as a graphic: which could, then, be incorporated into a Web page.


Not So Good Excerpts (including some grammatical problems)

♦ You ought to be able to justify the inclusion of whatever you choose to include, based on its relationship to the current experiment/research. If any given topic is included, its relationship to the current research should be made quite clear. Don’t just ramble on ad nauseam about photosynthesis, in general. Be selective about what you include, and why.

♦ The other effects have also been noted when treating a photosynthesizing cell with different wavelengths of light. [What other effects?]

♦ Chlorophyll is the most important of these pigments because it is essential for this process. [Which of the chlorophylls?]

♦ A Dutch physician, chemist, and alchemist was extremely interested in how they did this and so he performed many experiments. [Who did what?]

♦ Photosynthesis is a process that has mesmerized the world for centuries and will probably not ever be fully understood. [Most students don’t speak/write that way — this is a pretty-obvious, un-cited, direct quote = plagiarism.]

♦ Hydrogen and the carbon and oxygen of carbon dioxide are then transformed into a series of increasingly complex compounds that result finally in a stable organic compound, glucose, and water. [Since a bunch of people had this identical sentence, and most students don’t write this way, this is obviously an un-cited, direct quote. Did Neil Campbell say it first — is this from ch. 10 of your textbook? Is this more plagiarism?]

♦ Plants give off oxygen that represents the primary source of food for humans and animals. [We use oxygen to burn our food for energy, not as food.]

♦ Photosynthesis is the physico-chemical process by which plants, algae and photosynthetic bacterial use light energy to drive the synthesis of organic compounds. [This is a prime example of an un-cited, direct quote, more plagiarism!]

♦ Plants, when in the dark, use oxygen to make their energy, just like animals. [Neither plants nor animals make energy. Both do use oxygen to burn sugar for fuel, thereby extracting its energy for other uses.]

♦ He took and he isolated it. [Do not use the word “took” unless you really mean that someone obtained something and carried it to another place.]

♦ Where are phycobilins found? Do they occur in plants? How do they relate to our experiment [do they?]?

♦ These pigments, known as accessory pigments, broaden the spectrum of light energy. [Nope, the spectrum of light energy is “fixed,” and cannot be broadened by any pigment. What accessory pigments do is to broaden the spectrum of light which can be absorbed and used by a plant.]

♦ The energy from light boosts photosystem II to the primary electron acceptor. When it loses energy, it goes down to photosystem I. Between this action lies the cytochrome complex. . . At photosystem I, light is again absorbed and boosted to the primary electron acceptor. It then loses its energy and starts to fall. [I think some electrons got left out somewhere along the line??? To move to a lower energy level is not necessarily to “fall” in the sense in which a person falls down when (s)he loses his/her balance.]

♦ The chlorophyll molecule is capable of converting active light energy into a latent form, which is glucose, that is stored in food. [Glucose is not energy. Glucose possesses/stores potential energy as chemical energy in the bonds that hold its atoms together to make a molecule.]

♦ These pigments can be found on the spectrum. The slower the frequency, the more red the color will appear on the spectrum. [Nope, again. Various wavelengths of visible light, ultraviolet light, infrared light, x-rays, microwaves, etc. are all part of the electromagnetic spectrum (but even they are not “on” the spectrum, and one thing they all have in common is that they have no physical “bodies.” Pigments, on the other hand, are physical objects, chemicals, each with a given structure. Depending on the details of their chemical structures, various pigments can absorb, reflect, or transmit various colors of light. While it is true that, within the small portion of the spectrum which we call “visible light,” red light has longer wavelengths, lower frequencies — fewer waves/second, and less energy than other visible “colors,” the photosynthetic pigments in a leaf usually don’t move as fast as those in the paint on your car.]

♦ Photosynthesis has optimized its light-absorbing capabilities by making a series of pigments, covering more of the visible spectrum. [The process of photosynthesis is incapable of the conscious, rational thought-processes and decision-making necessary to systematically optimize its own capabilities. The photosynthetic pigments are not made by the process of photosynthesis. Rather, an evolutionist would probably explain it something like this: as the algal predecessors of plants evolved in water, and formed a variety of pigments in a variety of colors, those algae which possessed pigments capable of absorbing and using the available blue light were able to survive and pass on their genes, while those algae with pigments which were unable to make use of the available light died — natural selection.]

♦ My appologies to the real authors whose quotes appear above, but because my students didn’t cite their sources, I have no way of knowing who actually wrote those (other than, I suspect that at least some of them may be from ch. 10 of our textbook and may be credited to Neil Campbell:)

Campbell, Neil A. 1996. Biology, 4th ed. Benjamin/Cummings Publ. Co., Inc. Menlo Park, CA..

If anyone who reads this can identify the actual authors of any of the above quotes, please let me know.


Citing References — Bibliographic Format

As mentioned in your lab handouts, in biology, the accepted format to use is Council of Biology Editors (CBE) rather than some of the formats, such as APA or MLA, that you may have used in English class. A copy of the CBE Style Manual is available in our library. Additionally, a Web search for “council of biology editors” turned up a long list of references, including the following:


Copyright © 1998 by J. Stein Carter. All rights reserved.
Chickadee photograph Copyright © by David B. Fankhauser
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