Photosynthesis&Respiration

So this blog post looks like its going to be a rather big project, getting two content standards to fit in one blog post....(sadly I'm doing this the night before grades are final...oh well) The aim of this post is to basically convey my understanding of photosynthesis, respiration, and how the energy produced is used. Unlike a number of my peers, rather than do the green human project, I decided, in the interest of time, just to do a flat out explanation of the two processes. So here goes.....

Photosynthesis. Or, How to make your own food.......

Essentially, photosynthesis is the process by which photoautotrophs synthesize food (sugar) from carbon dioxide (CO2) using the energy from light. Sounds mighty dang simple right? Well, it mostly is. It happens like this: In oxegenic photosynthesis (literally photosynthesis that releases oxygen) Light energy is absorbed by proteins that contain chloroplasts which contain chlorophylls (by the way, chlorophylls are green because that is the part of the light spectrum they do not use). The chlorophylls store most of the energy in the form of ATP.

Chloroplast

The next step in photosynthesis is the oxidation of H20. Energy (ADP) is used to split the hydrogen and Oxygen molecules apart. The oxygen molecules are released (they can be used in respiration), and the hydrogens are kept. When CO2 is added to the process they each lose an Oxygen, which attach to some of the hydrogen molecules, forming H2O. The remaining Hydrogen, Oxygen, and Carbon then all get combined into glucose.

---CO2 can also be converted into sugars suing a process called carbon fixation. The most common type of carbon fixation in biological life is the Calvin cycle. The Calvin cycle describes the way that light energy is used in the creation of chemical free energy, stored in glucose. The key enzyme that makes the cycle run is called RubBisCO, found in the chloroplast stroma. The Calvin cycle includes a number of regulatory functions that prevent it from being respired (look at the second half of the post) into CO2 (preventing energy (ATP) from being wasted without a net gain). For more information on the Calvin cycle, click here.-----

The glucose can then be burned through cellular respiration.

Cellular Respiration Or:how you use your food

Cellular respiration is the process by which nutrients are broken down into ADP. The first kind of respiration is called aerobic respiration. Aerobic respiration requires oxygen to break down the nutrients. It has three main stages. Glycosis, Krebs cycle, and electron transport.

1. In Glycolysis (spliting sugars), Glucose, is split into two molecules of a three carbon sugar. In the process, two molecules of ATP, two molecules of pyruvic acid and two "high energy" electron carrying molecules of NADH are produced. Glycolysis can occur with or without oxygen. In the presence of oxygen (like in aerobic respiration), glycolysis is the first stage of cellular respiration. Without oxygen, glycolysis allows cells to make small amounts of ATP (fermentation).
2.  The Krebs Cycle (citric acid cycle) begins after the two molecules of the three carbon sugar produced in glycolysis are converted to a different compound (acetyl CoA). Through a series of intermediate steps, several compounds capable of storing electrons are produced along with two ATP molecules. These compounds, known as NAD (nicotinamide adenine dinucleotide...what is it with bio and big words?) and flavin adenine dinucleotide (FAD), are reduced in the process. These reduced forms carry the electrons to the next stage. The Krebs Cycle occurs only when oxygen is present but it doesn't use oxygen directly (in aerobic respiration).   
3.  Electron Transport requires oxygen directly. The electron transport "chain" is a series of electron carriers in the membrane of the mitochondria in eukaryotic cells. Through a series of reactions, the earlier mentioned electrons are passed to oxygen. In the process, a gradient is formed, and eventually ATP is produced.

Maximum ATP Yields: Prokaryotic cells can yield a maximum of 38 ATP molecules while eukaryotic cells can yield a maximum of 36. In eukaryotic cells, the NADH molecules produced in glycolysis pass through the mitochondrial membrane, which "costs" two ATP molecules.


Other kinds of cellular respiration include fermentation, where the pyruvate is converted to waste products, which when removed from the cell oxidizes the electron carriers, and anaerobic respiration wher unlike in aerobic, the oxygen is replaced by an inorganic acceptor (sulfur) is used. 

Enzyme Lab. With graphs.

A few weeks ago (if you haven't noticed there's about a three week period between the time we do stuff in class and the day I write a post for it) we did what was called the "Enzyme Lab". This lab consisted of mixing 3ml of H2O2 (hydrogen peroxide) with 3ml of water (H20) , and adding an enzyme (yeast) to start a chemical reaction that produces O2. The way the experiment works is the enzyme breaks the Oxygen molecules off of the H2O and H2O2 and releases them. We measured the reaction with a pressure sensor that was hooked up to my mac (which sucks slightly less...). Of course no experiment would be complete without a few variables, so we did the experiment three different ways each time changing one aspect of it (we repeated each set three times in order to gain an accurate representation of data). The first time we changed the concentration of the enzyme (10 drops, 20 drops, 30 drops, 40 drops.), the second time we changed the temperature of the solution be for adding the enzyme (Hot, cold, warm, and room temp). The third time we substituted the water (H2O) for a pH solution (2, 7, or 10).

Concentration-

   For this part of the experiment we varied the amount of enzyme that we added to the solution. The first time we only put 10 drops of yeast in. This gave us a rise of pressure of .02642 psi every .0626 minutes (known as the rate of reaction.) When we added 20 drops of yeast to the solution the amount of O2 produced was twenty times that of the 10 drops. You can tell this because the rate of reaction (.5102 psi per .626 seconds) is twenty time that of the  10 drop solution (.2643 psi every .0626 minutes).  At 30 drops the rate of reactions seems to have found a new pattern for every 10 drops the rate of reaction goes up .2 psi every .0626 seconds. The biggest gain in rate of reaction is when you go from 30 drops to 40 drops, it goes from .7294 psi/.0626 seconds to 1.673 psi/.0626 seconds. Personally, I suspect that the last one wasn't 40 drops, but more like 80 (Sierra  didn't know what a drop was ;).... ). What we can learn from this experiment is the greater the concentration of enzymes, the larger the amount of O2.

Temperature-

So now that we know what happens when we vary the concentration of enzymes in our solution, it is time to find out what happens when we vary the temperature of the mixture. For this part of the experiment we used the same mixture of H2O2 and H2O, but we kept the amount of yeast at a constant (25 drops). Instead we put one test tube of the base solution in the freezer (0 degrees celsius), left one at room temperature (25 degrees), warmed one up to 38 degrees, and heated one up to 80 degrees. What we cal learn from this is that enzymes really hate hot temperatures. 80 degrees Celsius was just too hot because at higher temperatures enzymes become denatured. Freezing the solution also had poor effects on the enzymes production of O2. The perfect temperature for  O2 production from enzymes is about 38 degrees Celsius. Room temperature yielded decent results compared to the other graphs, but 38 degrees just won the metaphorical race.  

pH Levels-

Sierra, Sierra, Sierra....... Ok it wasn't her fault this time that our data is all defunketated (not a word but...oh well). Actually it was an equipment error. There is no way that the enzymes were making negative O2. We determined over the course of this post that it was an equipment error, so disregard the graph. What was supposed to happen was the enzymes would produce the most O2 when the pH level was normal (7) and less at 4 and 10 (which the graph slightly shows). To produce the varied pH levels we replaced the 3ml of H2O, in the base solution, with 3ml of the different pH solutions.