Cellular respiration is a process humans do and Photosynthesis is for plants... right? Well only partially, photosynthesis is a process only plants do, but that's only because they are autotrophs and they make there own food. They also use cellular respiration after they get there food through photosynthesis. But you may not realize how complex those processes are, so here's how it works. We start with the ATP cycle.
The ATP cycle works like this: you have Adenine, a ribose, and three phosphates. The bond between the last and second phosphate is broken to release energy, which gives you ADP, an Adenine, ribose and two phosphates. To store energy back again you add on the third phosphate giving you ATP again. Then the cycle repeats. This is a process used in both Photosynthesis and Cellular Respiration.

Cellular Respiration: Oxygen + Glucose = Carbon Dioxide + Water and in chemical form is:  602 + C6H12O6 = 6C02 + 6H20. This is the process in which your cells convert glucose into energy in the presents of oxygen. It takes place in the mitochondria and it produces 36 ATP molecules of energy.  Now this may look like a rather simple thing, but the in depth process is far more complicated. If all of the energy it made were released at once, and never stored, most of it would be lost in the form of heat, and because your not catching on fire every time you work out, you know that its stores it. So your body's way of storing this energy is in ATP molecules. There are three main ways in which a cell captures ATP during cell respiration glycolysis, the kerbs cycle and the elctron transport chain, but the main one you need to understand right now is glycolysis. Glycolysis is the process were a glucose molecule is broken in half, producing two molecules of pyruvic acid (a three carbon compound), and also this process releases 4 high energy electrons, which are stored in NAD+, and held there until they can be transferred to other molecules. But your body only has so many NAD+, so what happens when there all filled with electrons? The answer is a process called Fermentation.

fermentation is when your body still produces ATP from food, but without oxygen, so its considered and anaerobic process. The two main types of fermentation are alcoholic and lactic acid fermentation. Alcoholic Fermentation produces carbon dioxide and well as alcohol. It's what yeast does to make your bread rise. Lactic Acid Fermentation is what your muscle cells do when you work out, that why you feel a burn, because of lactic acid build up. Through this process your NAD+ are regenerated so that glycolysis can continue. 

Photosynthesis: Carbon Dioxide + Water = Oxygen + Glucose and in formula is 6C02 + 6H20 = 602 + C6H12O2. This is the process that plants use to turn sunlight into food that they can eat, but people sometimes forget that this is only how they make food not how there cells get energy, so after photosynthesizing, a plant preforms cellular respiration to produce energy.

Availability of reactants.

OK, so first up you might be wondering how a plant can photosynthesize in the day and still have enough food to photosynthesize at night. You might also be thinking that maybe there's a link between how much light a plant gets and how much a plant photosynthesizes. Well you sir are correct, there is indeed a connection between the two, but not like you'd think. Most people assume that the more you put in the more you get, which is true, but it has a limit. Photosynthesize is a process which involves enzymes. Enzymes can only brake down so much food so fast, like us.
Think of it as an eating contest, your like an enzyme, braking down the 'food' in front of you. And lets also assume that your not new to it all so you pase your self. And they keep adding more food to your plate and you keep eating. Eventually you feel overloaded because no matter how much food they put on your plate, you can only eat so fast. This is what happens to enzymes, they brake down the material at a certain rate, so no matter how much light you give your plant, it will only grow at a certain rate. As shown in the chart to the left.

One thing you may not know is that plants are affected by temperature to, why do you think they all die in the winter? Its because there enzymes that brake down there food and such function better in heat. This is because when it gets cold the enzymes sort of 'freeze' and cannot function efficiently to maintain the plant. But on the other side of things, if it gets to hot the enzyme 'melts' and changes its shape so it can't brake down the substrates because they wont fit into the active site. So a chart showing how temperature affects plants would look much like a bell curve. (shown below)
A student poured a solution of bromthymol blue indicator into three test tubes. Then, he placed and aquatic plant in two of the test tubes, as shown below. He placed a stopper on each test tube and placed them all in the dark for 24 hours. Brothymol blue turns from blue to yellow in the presence of CO2.
a) Which process would you expect the organisms in the test tubes to carry out-- cell respiration, photosynthesis or both? When would you expect each process to occur?
In the sunlight, plants photosynthesize to make there food, and photosynthesis uses CO2, so the beakers would be blue, but when the beakers were placed in the dark, they would use cellular respiration to convert the food they made to energy they use to live.
b) What is the purpose of the brothymol blue? How can the student use this indicator to draw conclusions about the process that the aquatic plants are carrying out? When the plants are photosynthesizing, they use CO2 causing the brothymal blue to stay blue, but when it uses respiration, it would produce CO2 causing the solution to be yellow. So the reason for the solution would to indicate what process the plant was doing, and when it used that process.
c) Predict what will happen to the test tubes shown below after 24 hours in the dark. (explain in terms or cell respiration and photosynthesis) I predict that the test tubes with the plants in them will be yellow because of the presents of CO2 because the plants used cellular respiration during the absents of sunlight.
d) Assume that after 24 hours in the dark, the brothymal blue in test tubes 2 and 3 in the figure turned yellow. The students then placed test tube 3 in a sunny window. He left test tube 2 in the dark. Predict what color the solution in each test tube will be after the next 24 hours. I predict that test tube 3 will turn blue again because the plant will start to photosynthesis, and that test tube 2 will remain yellow because it's still in the dark and cannot photosynthesize so it will just keep using cellular respiration.



Mrs. B
11/27/2011 13:33

Autotrophs, not autographs :-)

This is a very thorough and well put together reassessment. The only thing I can find that you are missing is a lack of description of how PS and CR are affected by the availability of reactants and how PS is affected by changes in light intensity and temperature. If you can explain these, and I feel certain, you already can, then you would be at a level 4.5. As it is now, this reassessment is at a level 3.5.

Mrs. B
11/28/2011 18:37

On your graph comparing the rate of PS and light intensity, you just need to switch the labels. Rate of PS should be on the side and light intensity on the bottom.

Not all plants die in the winter, but some do.

Your hard work is evident, and your learning has improved tremendously because of it.

Level 4.5


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