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. 

 

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!