Photosynthesis (snow week)

Describe the overall structure of a chloroplast and where the two major steps of photosynthesis take places. Talk about the thylakoid and the stroma. Discuss the light reactions (Photosystems I and II, ATP synthase, the electron transport chain) and the Calvin Cycle.


The chloroplasts are the specific sites of photosynthesis in PLANT cells (animal calls do not have chloroplasts). The chloroplast has an inner and outer membrane, the stroma (site of calvin cycle / light independent reactions – a fluid filled area) and the thylakoids. The thylakoids are the sites of the light dependent reactions. They contain chlorophyll which is a colored compound that absorbs light. Chlorophyll is what makes plants green.


The photosynthesis process begins with the light dependent reactions, in the thylakoid. So it all starts with Photosystem II (not I). 2H2O and light come in and water is split up into O2 and 4 H+. The water provides the high potential energy electron for the electron transport chain. The electrons move down the chain to Photosystem I. More light is introduced as well as 2 NADP+ and 2H+, 2NADPH are produced at this step to be used later in the Calvin Cycle. The last step is ATP synthase which utilizes the H+ gradient and stamps 3Pi onto 3ADP to produce 3ATP which are sent to the Calvin Cycle (outside of the thylakoid) for the last steps.


The Calvin Cycle (light independent reactions or dark reactions) has three phases: Carbon fixation, Reduction, and Regeneration. The Calvin Cycle starts with 3CO2 coming in. Carbon fixation occurs which means that the carbons are bonded to something to make them usable. 3CO2 is combined with a P from the 6ATP (6ADP are left) to make 6PGA. Then during reduction, the 6 NADPH from before are broken into 6NADP+, 6H2O, and 6Pi and 6PGAL are produced but one goes off and you are left with 5. Then 3ATP come in and regenerate to 3ADP and 3Pi and 3RuBP are produced. Then the it bonds with 3CO2 and the cycle is started over again. unnamed.png


Cellular Respiration

Ap bio seems to just be getting harder and harder. This week was no exception. This week was all about cellular respiration, the steps that go into it and the molecules that make it possible. Cellular respiration is the way our body transforms the food we eat into energy or ATP (adenosine triphosphate). The food must be broken down in the presence of oxygen within our bodies. The reaction is C6H12O6 + 6O2 -> 6Co2 + 6H2O + energy. The 4 main steps of cellular respiration are glycolysis, pyruvate oxidation, civic acid cycle (not Krebs cycle), and oxidative phosphorylation. The process begins with glycolysis, the only process that is outside of the cytoplasm of the cell. Glycolysis is one of the processes that produces ATP and 2NADH when taking in glucose. The next process is pyruvate oxidation, this occurs inside the cytoplasm of the cell. Pyruvate oxidations takes 2 pyruvate from glycolysis and produces 2 CO2 and 2 NADH. This is the only step that does not produce ATP. The next step is the citric acid cycle, this also occurs within the cytoplasm. This step takes 2 AcetylCoA from the previous step and produces 4 CO2, 2ATP, 6NADH, and 2FADH2.  The last step is the big ATP producer – Oxidative Phosphorylation. This process also occurs in the cytoplasm. This step uses 6O2 to produce 34 ATP and 6 H2O. All these steps combined are one of the most important process that occur in our body.

With out the mitochondria and cellular respiration we would be blobs of nothing that didn’t move. We would be dead. This is why mitochondria should have won the election. Without the mitochondria you would be nothing.

Besides the devastating loss this week it was a pretty ok week. The POGIL cleared things up a lot and re watching the Bozeman video was also very helpful. I have high hopes this unit will be clearer than others. I am having a little bit of trouble with understanding the citric acid cycle and what actually happens. Other than that I think I might actually understand whats going on for once!


Free Energy

From a young age we are taught that nothing in this word is free. This week Mr. Dunn told us otherwise. This week we learned about free energy and its purpose. What free energy is exactly is still a little fuzzy in my brain. The three main things we get from free energy are organization, growth, and reproduction. All energy comes from the sun (or environment). Without this available free energy from the sun our lives would probably not exist today. We utilize this free energy through metabolism (sum of all the chemical reactions in our body). Glycolysis is a series of reactions that happens in our bodies and its cool because we can jump into it at any point in the process depending on the nutrients or energy we are given (its the breakdown of glucose into pyruvate). How energy get to us from the sun is because plants take it in and create sugars and oxygen through photosynthesis. The energy is pasted on through consumption; we eat plants or other things eat plats and then we eat them. Excess free energy goes into storage. Disruptions in free energy can lead to death in an individual and can change a population or ecosystem. To maintain life we need order which requires a constant supply of energy. We also learned about the two laws of thermodynamics. The first one states that energy can never be created or destroyed just changed. The second law is that every time we convert energy, there is more entropy in the universe, or more disorder. This only applies to a closed system. When we create more order, it makes the universe more DISordered. This works because it is an open system not a closed system. This week connected to Big Idea 2.a. Big Idea 2.a talk about free energy and how every living thing needs it and utilizes it to live.

The lab that went along with this week confused me. We made little yeast balls and then put them in hydrogen peroxide and timed how long it took them to go from the bottom of the beaker to the top. Then we tested the yeast balls in different temps. of hydrogen peroxide. We went to 55˚ C and 10˚ C. When it was hotter it went faster and when it was colder it went slower. Full discloser I’m not completely sure why we did this lab or what it taught us. I don’t know how it connected to free energy or metabolism. If someone can explain, please do.

I don’t know how to get rid of this:

All in all I found this week to be a 7 on the toughness scale (1-10, 1 being the easiest). Maybe something that made the week hard was that I don’t quite understand what free energy mean. I sorta understood the idea but I don’t feel strong enough on the unit to take the test. This has been a very hard and confusing unit for me. I don’t understand a lot of chemical reactions or bonds and things like that. It’s hard for me to understand when I can’t physically see it. That’s what made this week so hard. I can’t visualize whats happening in glycolysis and within the body. I also don’t fully understand what’s happening when the universe is becoming disordered. I understand that order in our body is the cells becoming more defined and things like that and evolution is ordered but then what is disorder? We don’t un-evolve. That’s my main questions from the week. The main take away from the week, however, is that yeast balls are super cute.