BS 161 Exam 3 Questions Marking Scheme

BS 161 Exam 3 Questions Marking Scheme Which of the following sequences CORRECTLY represents the flow of energy through living systems? - Answer -light → photosynthesis → carbohydrate → cellular respiration → ATP → heat Where is the photosynthetic electron transport chain located in plant cells? - Answer -in the thylakoid membranes of the chloroplast In a thylakoid membrane, absorbed light energy is passed from one chlorophyll molecule to another until it is: - Answer -passed to a reaction center. During photosynthesis, _____ is reduced to _____. - Answer -carbon dioxide; sugar Which of the following CORRECTLY lists the three steps of the Calvin cycle? - Answer -carboxylation, reduction, and regeneration Which of the following CORRECTLY describes the role of rubisco in the Calvin cycle? - Answer -Rubisco incorporates CO2 from the atmosphere into an organic molecule. How many CO2 molecules must enter the Calvin cycle for each molecule of triose phosphate that can be exported from the chloroplast? - Answer -3 In the Calvin cycle, NADPH is: - Answer -oxidized. Which step of the Calvin cycle would be affected first by a lack of NADPH? - Answer -reduction Which of the following are products of the light-dependent reactions of photosynthesis that are required by reactions in the Calvin cycle? - Answer -ATP and NADPH Which of the following are produced directly as a result of the movement of electrons through the photosynthetic electron transport chain? - Answer -ATP and NADPH During photosynthesis in plants and algae, _____ is being oxidized and _____ is being reduced. - Answer -H2O; CO2 In plants and algae, _____ is the source of the electrons needed for photosynthesis. - Answer -H2O In plants and algae, which of the following is a by-product of photosynthesis? - Answer -O2 Which one of the following is NOT a product when photosystem II oxidizes a molecule of water? - Answer -carbon dioxide Which of the following CORRECTLY lists the path taken by electrons through the light dependent reactions of photosynthesis? - Answer -water → photosystem II → cytochrome b6f → photosystem I → NADPH Why is the photosynthetic electron transport chain sometimes referred to as the "Z scheme"? - Answer -Because the energy level of the electrons increases and decreases and increases and decreases. As electrons flow through the light-dependent reactions, they become associated with several molecules and molecular complexes. When do the electrons have the GREATEST amount of energy? - Answer -when they are associated with photosystem I As electrons flow from one photosystem to another, the amount of energy present in the electrons decreases. How does the plant cell use the energy lost by the electrons? - Answer -The energy is used to create and maintain a proton gradient. In the chloroplast, cytochrome b6f is an important complex in the photosynthetic electron transport chain because it accepts electrons from photosystem II and donates them to photosystem I. Another vital function of cytochrome b6f is that, during its reduction-oxidation cycle, it moves _____ from the _____. - Answer -protons; stroma into the thylakoid lumen Which of the following statements must be true in order for ATP synthase present in chloroplasts to function properly? - Answer -The pH of the stroma must be higher than the pH of the thylakoid lumen.