BOT 331 Exam 3 Questions & Answers Correct 100%

True/false, if false explain why Accessory pigments transfer excited electrons to the chlorophyll a molecules at the reaction center of PSII. - Answer False, accessory pigments transfer energy, but do not transfer electrons. Right, so the statement is False - electrons are NOT transferred True/false, if false explain why The flow of electrons through the ATP synthase is coupled to generating ATP. - Answer False, the flow of protons, NOT electrons, through the ATP synthase is coupled to generating ATP. Yes, but electrons do not flow through the ATP synthase True/false, if false explain why Carbamylation is when Rubisco catalyzes a covalent bond between CO2 and ribulose 1,5-bisphosphate.2 - Answer False, carbamylation is forming a covalent bond between CO2 and an amino acid of Rubisco, and is involved in regulating Rubisco activity. True/false, if false explain why The Calvin-Benson cycle is also known as the C4 pathway. - Answer False, the Calvin cycle is also known as the C3 pathway, because its output is a 3-carbon molecule (glyceraldehyde 3-phosphate), in contrast to the output of C4 fixation being a 4-carbon molecule (oxaloacetate and then malate) True/false, if false explain why Iron is required in greater amounts than copper for the light reactions. - Answer True Copper is the electron carrier of plastocyanin, but iron is the electron carrier for numerous parts: cytochromes b, c and f and iron-sulfur clusters in the b6f complex, PSI and ferredoxin True/false, if false explain why During the light reactions, extracting electrons from H2O and donating electrons to NADP+ both contribute to increasing the proton motive force. - Answer True Extracting electrons from water (2 H2O) results in 4H+ as well as 2 O2, and when electrons are donated to NADP+ a covlant bond with a H+ forms to yield NADPH. Both events increase the difference between protons in the lumen versus the stroma side of the thylakoid membrane. True/false, if false explain why The accessory pigments include carotenoids and chlorophyll b, but not chlorophyll a. - Answer False, chlorophyll a is an accessory pigment, as well as there being chlorophyll a at reaction centers. True/false, if false explain why An electron carrier that accepts an electron is reduced, not oxidized. - Answer True. Oxidation happens when there is a loss of electrons, therefore accepting an electron would be a reduction. When electrons are NOT flowing through the light reactions, Rubisco's active site has a covalent bond to a sugar that inhibits Rubisco. However, the sugar is removed shortly after the light reactions become active and electrons are flowing. How is the flow of electrons in the light reactions connected to the removal of the sugar from Rubisco's active site? - Answer The sugar is removed by an enzyme called Rubisco Activase, which is active only after its disulfide bridge is broken by being reduced. Thioredoxin donates the electrons to reduce the disulfide bridge. Thioredoxin gets the electrons from thioredoxin reductase, which gets the electrons from ferredoxin, which gets the electrons from the light reactions - from photosystem I. What is the output of 3 cycles of the Calvin-Benson cycle? - Answer 1 molecule of glyceraldehyde 3-phosphate 5 molecules are used to regenerate ribulose 1,5 bisphosphate Explain how leaves are green. - Answer Leaves are green because chlorophyll a is the most abundant pigment in leaves, and chlorophyll a reflects green wavelengths of light, while absorbing blue and red wavelengths. Both cyclic and non-cyclic electron flow depend on electrons being extracted from water. Do you agree or disagree? Explain your answer - Answer I disagree. Cyclic electron flow involves excited electrons of P700 moving to ferredoxin, then to b6f complex, then to plastoycanin and back to P700, so does not need electrons extracted from water. In contrast, non-cyclic electron flow moves electrons from P680 to NADP+, and the P680 electrons lost are replaced by electrons extracting from water. True/false, if false explain why Rubisco absorbs photons and uses the energy to 'fix' CO2 into a sugar. - Answer False, Rubisco does NOT absorb photons. Which protein complex of the light reactions has electron carriers that are manganese atoms? ATP synthase Photosystem I Cytochrome b6f complex Oxygen-evolving complex - Answer Oxygen-evolving complex