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Squishy Star
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 Posted - 2004/05/06 : 23:24:39
[GENERAL discussion]
Yeah...well I'm in need of some help with my Science Project. I am going to develop a photo onto a plant leaf through the process of Photosynthesis. Now, I need to explain why this is possible to occur. I found something from the internet that may be the explanation but I'm have a little difficulty understranding it. Can someone please explain the following in much more easier words to understand?
>>During the light-independent (dark) reactions of photosynthesis, CO2 is reduced by NADPH and ATP produced during the light-dependent reactions. This process, often referred to as “carbon fixation,” results in the production of carbohydrates, lipids, proteins, and other organic molecules. Generally, the first-formed products of carbon fixation are carbohydrates, such as glucose and sucrose. When there is an excess of these simple sugars, starch is formed for more efficient storage of the reduced carbon.
Because the dark reactions depend upon the presence of ATP and NADPH produced by the light reactions, they generally only take place when the plant is lit. The only exception to this is the situation in CAM (Crassulacean Acid Metabolism) plants, in which CO2 is first fixed by PEP carboxylase during the night, producing malic acid. During the day, this malic acid is released from the vacuole, then it is decarboxylated to provide CO2 for the Calvin Cycle. Rubisco, the enzyme that fixes CO2 in the Calvin Cycle, is light activated, so the Calvin Cycle can only take place when the plant is lit. It is the Calvin Cycle that ultimately leads to the production of storage carbohydrates.
F. F. Blackman demonstrated that the rate of photosynthetic carbon fixation depends upon the light intensity (among other things). We will demonstrate this using an indirect method of assessing photosynthesis. Specifically, we will monitor the accumulation of starch in a plant leaf, and we will see how starch accumulation depends upon the intensity of light striking the leaf.
Part 1: The influence of light intensity on starch production in photosynthesis.
Starch is a combination of straight chain and branched chain polymers of glucose that is used as an energy storage molecule by plants. Starch is synthesized in the chloroplasts of plants during the dark reactions of photosynthesis. Iodine is a specific stain for starch that produces a dark blue color when starch is present. We will use iodine to localize starch in leaves that have been carrying out photosynthesis in various light intensities.<<
...Anyone??
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Brian K
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Posted - 2004/05/07 : 00:06:28
i understand the photosynthesis part but how are you wanting to use it in making a photo on a leave?
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Squishy Star
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Posted - 2004/05/07 : 00:17:01
It's going to work...
And I think this explains why or like how this is able to happen.
Here, check out: http://www.northern.edu/ramsayj/Botany/carbonfixlab.html
That's basically what I'm going to do.
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milo
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Posted - 2004/05/07 : 08:48:07
alright, i'm a bit rusty on the bio, but basically what is happening is this (forgive my terminology).
Photosynthesis obviously needs light as we've learned since... kindergarden? but there are two processes which go on (light and dark). the light process is what uses the sun to break down CO2 and H2O (i think those are the two molecules) for use. once there are broken down they begin going through the three parts of photosynthesis. As described the krebs cycle (2nd step?) needs light to happen so the raw reactants can be prepared for it so it can work (bunch of steps that essentially result in the initial enzyme used again and some nifty products (including ATP, NADPH, and one other DPH)). Now once this is done we no longer need light so the final phase (the one with the electron chain where all the ATP is pumped out in mass?) can happen. Seeing as the steps needed to make the reactants for this process are light dependant, the dark phase usually happens when light is present (but it isn't needed).
CAM is what desert plants do so they don't lose water in the heat. Essentially the same stuff but the necessary molecules are picked up at different times to avoid killing itself. you're not using a cactus so don't worry about it (though it would be an impressive point to cover).
And the trick with the iodine... as described (and hopefully you've done in a hs lab by now) iodine reacts with startch (brown -> blue/purple). Seeing as the product made by photo synthesis is glucose (sugar), the plant is smart and makes more than is needed and stores them making compact chains of glucose -> startch. Now it seems by using the photopaper, the amount of light let through will vary with the picture (think of a grey scale). more light through -> more photosynthesis -> more glucuse -> more startch -> more blue. so this grey scale turns into a blue/purple scale (from light to dark). and is on your leaf. You need to stop photosynthesis first so the starch is gone, otherwise you'll just get a big ugly blotch.
i did a report on this a long time ago, i'll try to find it and post a link.
*edit - the project was a big ass flow chart, can't exactly scan it in. while most of the info is most likely techinically incorrect, the theory of what is going on should be ok*
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Edited by - milo on 2004/05/07 08:54:20 |
Squishy Star
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Posted - 2004/05/07 : 18:45:43
I'm not sure if you answered this already, but how is photosynthesis able to develop a photo from a black and white negative onto a leaf?
What do you mean by "the product", iodine?? So if that's what you mean, are you saying that the plant makes more compact chains of glucose to store this starch from iodine? Oh wait, that's wrong! Okay...so obviously the photo was developed by photosynthesis. Frap! I'm getting really confused because the project displayed on that site isn't exaclty what I'm doing but very similar. Can you just tell me how photosynthesis is able to develop a photo!? ...I'm still not understanding the thing with the starch or whatever. Ugh! This is very frustrating, knowing my project is due on either Monday or Tuesday and I am not understanding a thing!!
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milo
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Posted - 2004/05/08 : 01:40:03
the photosynthesis would indirectly make the photo... lemme rephrase what i said...
one of the products of photosynthesis is glucose. since the plant is going to make more than it needs at one time, it's going to need to store it. to store it, the glucose bind together to make a long chain of 'em. this long chain is called starch (go get bread (starch) and chew on it for a while if you don't believe me... the chains break down from the saliva and it gets sweet (glucose/sugar) weird eh?). So the cells and surrounding area have all these huge starch molecules now after photosynthesis is made. Now, from what it seems, the photo is indirectly made from this using iodine. Iodine is reactive with starch and turns from a brown color to a blue/purple color. Seeing as the photo is all about light and how much is absorbed and what not, when laid out over a leaf, the amount of light that reaches the leaf is restricted based on the parts of the photo (lighter areas would let more light through than darker areas ect.). So therefore the amount of photosynthesis that can occur would be dependant on the amount of light that reaches it. so therefore the amount of starch produced would depend on that as well. The lighters areas -> more starch while the darker areas -> less starch. add the iodine in, it's going to react with the starch, the more starch, the more the reaction can take place so it will be darker/bluer in the areas that have a lot of starch.
So by controlling the amount of light that reaches the leaf with the photo, you're controlling photosynthesis, which means you're controlling the amount of starch produced, which controls the amount that iodine reacts.
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Chicken
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Posted - 2004/05/08 : 02:14:52
Whoa, sorry Eri... I'm an engineer not a scientist. Math is more my thing, not science, so I'm totally lost here, lol. Sorry I can't help, but I have to say that this project sounds VERY interesting and I'm sure when you manage to pull it off, you will score an awesome grade. I'm quite impressed... I never would have done a project like that when I was 14. Hell, I'm 19 and I STILL wouldnt do it, hahaha
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Squishy Star
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Posted - 2004/05/08 : 03:05:57
Thank you sooo much, Milo!!!!!
Heh. I should put your name on the Science Project too...It's nice to know that there are people here that know more than just hardcore. =X Whoops! How do you know this stuff so indepth anyways??
--OH MY F****** GOSH! *screams* You know how I'm supposed to put the plant in a dark place for 48 hours? Well I put it in MY closet in MY room and people keep opening it! Ugh! This is not going to work out! Why can't people just leave my stuff alone!?
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Edited by - Squishy Star on 2004/05/08 03:21:58 |
milo
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Posted - 2004/05/08 : 04:12:09
no problem. I'm a chemistry and physics major in university and i did all that AP crap in hs. leaning towards environmental chemistry right now. i'd recommend checking out an AP bio text book for a better explanation on all this stuff as far as getting down to the details go.
and as far as keeping it dark... put it in a box in the closet so when it opens there is still no light =P
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Squishy Star
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Posted - 2004/05/08 : 04:20:58
...I already looked. I don't have any boxes.
As for checking out AP Bio Text books..........my project is due on either Monday or Tuesday. I won't have my project completed until atleast Wednesday! x.x
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Squishy Star
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Posted - 2004/05/08 : 05:53:23
(Time: 11:52 PM)
Is this "Conclusion" okay?
>By following the steps above I have learned that there are alternatives for developing photographs. Apparently my hypothesis has been proven to be correct. During carbon fixation, starch is formed for more efficient storage because of an excess of sugars. By putting the plant in darkness I had stopped the binding of glucose which forms starch. Because photographs are all about the light and how much is absorbed, the amount of light reaching the leaf is restricted by the parts (lights and darks) of the photo. When putting the plant back into light the photosynthesis process is started all over again. The amount of photosynthesis the covered area receives really depends on how much light can pass through the negative. Obviously the amount of starch that is produced is affected by the amount of photosynthesis the plant receives. Apparently the most amounts of starches would be found under the lighter parts of the photograph on the leaf. The more starch there is, the more reactions there will be, caused by iodine.
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milo
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Posted - 2004/05/08 : 06:42:14
well hopefully your teacher understands =P
as for the conclusion:
carbon fixation does not make starch. starch is made by dehydration synthesis (i think) of glucose molecules to form a chain. carbon fixation is a part of the photosynthesis process. and by putting the plant in darkness, you stopped the plant from doing photosynthesis (remember the dark phase and everything after it is not directly dependant on the presence of light). the darkness forces it to use up it's energy and causes the chloroplasts to move since they aren't being used. and the most of the starch would be found under the areas where the most light went through, not necessarily the lighter parts of the photo (i know i said that but i don't know how photos work, just used to to try to help explain). and the degree of how much iodine reacts is dependant on how much starch there is. more starch, more reaction -> darker spot. the iodine does not cause the reaction, it is the reaction.
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Squishy Star
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Posted - 2004/05/08 : 16:06:53
Okay...now I need to
rip it off my display board
and rewrite it.
-.0 *goes insane*
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mark-ireland
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Posted - 2004/05/08 : 17:05:41
I saw something like that before on a daytime telly program over here and it looked fuc*king brilliant.
mark-ireland
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Squishy Star
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Posted - 2004/05/08 : 21:49:02
How's this: ?
>By following the steps above I have learned that there are alternatives for developing photographs. Apparently my hypothesis has been proven to be correct.
During photosynthesis glucose is formed which is a carbohydrate. During dehydration synthesis the glucose is combined with other glucose’s forming starches. Since photosynthesis is not light-dependent, reactions do occur in the dark. This is known as carbon fixation. In the light-independent reactions of photosynthesis, CO2 is reduced by NADPH and ATP. NADPH stands for Nicotinamide Adenine Dinucleotide Phosphate and ATP stands for Adenosine Triphosphate. By putting the plant in darkness the light-dependent reactions of photosynthesis is stopped. The darkness forces the plant to use up it’s energy which then causes the chloroplasts to move since they aren’t being used. So how much starch that is accumulated in an area depends on the intensity of the light and how much light was able go through the negative. Because iodine and starch react, the reaction of iodine is dependent on how much starch there is. The darker areas indicate the area with the most amounts of starch. Since iodine and starches react, the more starch there is means more of a reaction there will be.
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milo
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Posted - 2004/05/08 : 23:46:20
photosynthesis is light dependant, but the later phases aren't. i'd really recommend reading a book or looking up online about carbon fixation and when the different chemicals come into play, i don't know if what you're saying is correct. also besure to say something about the purpose of putting the leaf in the dark. it kind of acts as to clean the slate of the leaf so nothing is there. bringing the light back through the photo causes it to begin photosynthesis again in those areas withn light and the degree of howmuch stuff is made is dependant on how much light and blah blah blah.
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