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.

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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.

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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 2

Compare and contrast Anaerobic cellular respiration and Aerobic cellular respiration. In your answer, address glycolysis, the citric acid cycle, oxidative phosphorylation, lactic acid fermentation, alcohol fermentation, NADH, FADH2 and ATP.  At the most basic level, the difference between Anaerobic and Aerobic respiration is that Aerobic respiration uses O2 and Anaerobic doesn’t. Aerobic also produces much more ATP than Anaerobic does (28-38 vs. 6ish). Both types of respiration include glycolysis in the cytosol and produce 2ATP and NADH. Only aerobic respiration has the citric acid cycle (produces 2 ATP and FADH2) and oxidative phosphorylation (produces 26-28 ATP) both of which occur in the mitochondria. Lactic acid and alcohol fermentation are both used in anaerobic respiration. In lactic acid fermentation, pyruvate reduced by NADH, forms lactate. No  CO2 is released (2 ATP produced). With alcohol fermentation, pyruvate is reduced to ethanol in 2 steps; 1. CO2 released from pyruvate and 2. acetaldehyde reduced to ethanol.

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Explain why the disruption of chemiosmosis and the proton motive force can be detrimental to eukaryotic organisms. Provide a real life example. When is chemiosmosis (energy coupling mechanism that uses energy stored in the form of a H+ gradient across a membrane)  and the proton motive force (the gradient of hydrogen ions) are disrupted a eukaryotic organism can not produce ATP and you would see mass cell death and ultimately the death of the organism because no energy is being produced. A real life example is cyanide poisoning. Cyanide damaged the mitochondria and prohibited the production of APT and killed people.

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Compare and contrast obligate and facultative anaerobes. Obligate anaerobes and facultative anaerobes carry out fermentation. But only obligate anaerobes carry out anaerobic respiration, but cannot survive in the presence of O2. On the other hand, facultative anaerobes can carry out cellular respiration.

In the following redox reaction, identify which molecules have been oxidized and reduced. Also identify the reducing agents and the oxidizing agents.

C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy

Carbon is oxidized due to the conversion from C6 → 6CO2 (looses electrons) this makes carbon the reducing agent.

Oxygen is reduced by taking electrons from the less electronegative Carbon (O6 → 6CO2), making oxygen the oxidizing agent.

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