BILD 1 Week 6 section materials(asynch)

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UCSD BILD 1: The Cell Section, Week 6 UCSD BILD 1: The Cell Adapted from Wisner, 2022 Question 1. Below is the overall reaction of photosynthesis. Instead of writing C 6 H 12 O 6 (glucose) as a product of photosynthesis, I wrote (CH 6 O) n. (CH 6 O) n is the generic notation for indicating a carbohydrate. Photosynthesis creates a carbohydrate (G3P) that the plant may use to make glucose, but it also may use it to make other carbohydrates like starch. CO 2 + H 2 O + light energy → (CH 6 O) n + O 2 A. Which molecule is the electron donor? Which is the electron receiver? Question 2. As part of an experiment to understand the photosynthesis, scientists performed the following experiment. They gave algae that do photosynthesis some carbon dioxide labeled with heavy oxygen, CO 18 2 . Then, they analyzed the oxygen gas given off by these plants. The oxygen gas did not contain any heavy oxygen. A. What conclusions can be drawn with certainty from this experiment alone ? Choose all that apply. 〇 The oxygen atoms in carbon dioxide do not become part of oxygen gas. 〇 The carbon atoms in carbon dioxide become part of glucose. 〇 None of the above. B. Justify why you chose or did not choose answer choice, “The oxygen atoms in carbon dioxide do not become part of oxygen gas.” in part a. (suggestion: 1 -2 sentences) C. Justify why you chose or did not choose answer choice “The carbon atoms in carbon dioxide become part of glucose,” in part a. (suggestion: 1 -2 sentences). D. Which of these are true statements about photosynthesis? Choose all that apply. 〇 The oxygen atoms in carbon dioxide do not become part of oxygen gas. 〇 The oxygen atoms in carbon dioxide become part of glucose. 〇 The oxygen atoms in water do not become part of glucose. 〇 The carbon atoms in carbon dioxide become part of glucose. Question 3: Fill in the table below: Where does it occur? (be specific) What are the inputs (reactants)? What are the products? Light Reactions In photosynthesis, water (HO) is the electron donor, providing electrons during the light-dependent reactions, while carbon dioxide (CO2) is the electron receiver, accepting these electrons during the light-independent reactions. This conversion of light energy into chemical energy results in the formation of carbohydrates, like glucose [(CH6O)n], and the release of oxygen (02) as a byproduct I chose the answer choice "The oxygen atoms in carbon dioxide do not become part of oxygen gas" because the experiment's result clearly shows that the oxygen gas produced by the plants did not contain heavy oxygen, implying that the oxygen atoms in carbon dioxide were not used to produce the oxygen gas. This is a direct and logical conclusion based on the experiment's findings. I did not choose the answer choice "The carbon atoms in carbon dioxide become part of glucose" because the experiment provided no direct evidence or information about the fate of the carbon atoms in carbon dioxide during photosynthesis. The absence of heavy oxygen in the oxygen gas does not provide information about the fate of carbon atoms, so this conclusion cannot be drawn based on the experiment's findings. Light reactions occur in the thylakoid membrane of the chloroplasts. The inputs for light reactions are light energy, water, and ADP (adenosine diphosphate) + inorganic phosphate (Pi). The products of light reactions are oxygen, ATP (adenosine triphosphate), and NADPH (nicotinamide adenine dinucleotide phosphate). ·

UCSD BILD 1: The Cell Section, Week 6 UCSD BILD 1: The Cell Adapted from Wisner, 2022 Calvin Cycle (also called Light- independent reactions) Based on what you wrote in the table, what is the overall purpose of the light reactions? Based on what you wrote in the table, what is the overall purpose of the Calvin cycle? Question 4 Rubisco normally incorporates carbon dioxide into organic molecules. However, sometimes, it uses oxygen gas (O 2 ) instead. This process is called photorespiration. a. Does photorespiration occur during the light reactions or the Calvin cycle? How do you know? (suggestion: 1 sentence) b. Would this be beneficial for the efficiency of photosynthesis? Explain and justify your response. (suggestion: 2-3 sentences) The Calvin Cycle takes place in the stroma of the chloroplasts. The inputs for the Calvin Cycle are carbon dioxide, ATP, and NADPH. The products of the Calvin Cycle are glucose and other carbohydrates. The overall purpose of light reactions is to capture light energy and convert it into chemical energy in the form of ATP and NADPH. Additionally, light reactions generate oxygen as a byproduct through the photolysis of water. The overall purpose of the Calvin Cycle is to use the chemical energy (ATP and NADPH) generated during the light reactions to fix carbon dioxide and synthesize organic molecules, particularly glucose and other carbohydrates. The Calvin Cycle is the process responsible for converting inorganic carbon (CO2) into organic compounds, which serve as energy-rich storage molecules for the plant. Photorespiration occurs during the Calvin cycle. This is evident because the process involves the oxygenase activity of the enzyme rubisco, which is a key enzyme in the Calvin cycle, and it interferes with the normal carbon-fixing function of rubisco by using oxygen instead of carbon dioxide. Photorespiration is not beneficial for the efficiency of photosynthesis; in fact, it is considered a wasteful process. Unlike the Calvin cycle, which leads to the synthesis of carbohydrates, photorespiration results in the release of carbon dioxide without the production of useful organic compounds. This process can reduce the overall efficiency of photosynthesis and is often considered a side reaction that competes with the desired carbon-fixing pathway.

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