Photosynthesis Practice Answers PDF

Preview

Summary

Answers for photosynthesis questions for Lab Exam #1...

Description

Pho Photosy tosy tosynt nt nthes hes hesis is la lab b ans answe we wers rs

1. Since the pigments are in the LUMEN of the vacuole you must use an aqueous solvent to extract them. In lab the more hydrophobic (less hydrophilic) a pigment the further it migrated. 2. The blank contained DNS as we are looking for an increase in absorbance with product (the DNS would contribute to the background). In the PSN lab we are looking for a decrease and as such the blank does NOT contain DCPIP. 3. Emission must be of less energy (longer wavelength) accompanied by heat. 4. Since there is sucrose present in the chloroplasts the outer membranes will remain intact. Thus the DCPIP would not be adjacent to the thylakoid and you would not expect reduction of DCPIP. 5. In lab you looked at acetone extracts of chloroplasts. These extracts fluoresce greatly because the excited pigments cannot transfer an electron, instead they release the energy as fluorescence and heat. 6. Positive control is with light (you see a rate) and the negative control is in the dark (allows one to take into account the reduction of DCPIP that occurs independent of light). 7. The light reactions occur in the thylakoid membranes (where the photosystems and light harvesting complex (LHC) are located) and the Calvin Benson cycle occurs in the stroma. There are no structures known as “thylakoid envelopes”. Even if you thought it read chloroplast envelopes it would not be correct because they do not contain the photosystems or LHC. 8. Green wavelength is the least effective at promoting photosynthesis and would produce the least amount of O2 and the bacteria would migrate to areas of higher O2 concentration (other wavelengths). 9. Photons excite the pigments which elevate the orbital of electrons. Since these high energy electrons were used to generate ATP and NADPH we know they were involved in the capturing and charge separation reactions. Fluorescence would have not been used to do work. 10. Rank the molecules in order of hydrophillicity M3>M2>M1 and thus the order from lowest Rf to highest value is M3. M2, M1. 11. The ionophore results in the increased movement of electrons but decreased ATP production because there is NO H+ gradient.

12. Light dependent reactions produce O2, NADPH + H+ (by reducting NADP+), ATP. 13. PS II reaction center receives electrons from water and PS I reaction receives electrons from the electron transport chain with PC being the donor. (Ferrodoxin is reduced by PS I and donates electrons to NADP+ which is not part of the reaction center.) 14. Since the carboxylase activity occurs when CO2 levels are so low (especially compared to the oxygen levels and oxygenase activity) the Km for the carboxylase activity is much lower. 15. The light must be absorbed for work to be done.

16. Rates of O2 production would match the rate of electron transport. Thus light + methylamine would result in a faster production of O2. 17. Cyclic electron transport chain does NOT produce oxygen. Oxygenic photosynthesis involving both photosystems (non-cyclical PSN) produces oxygen by the oxidation of water. 18. Figure 2 illustrates lysed chloroplasts where the outer membranes are ruptured (envelope membranes) but the thylakoid membranes remain intact. 19. Since the mobil phase is the more hydrophilic phase chlorophyll b should have a larger Rf value....