Problem Set 6

how many photons/excitons are required by each center to complete the oxidation of two water molecules to oxygen?

4 photons/excitons

what are the two compounds that are products of the first set of reactions that are needed for the second set?

ATP and NADPH

what are the two separate sets of reactions in photosynthesis?

Calvin cycle and light reaction

what happens when a chlorophyll molecule absorbs a photon of red light?

an electron is excited from the ground state to the first excited singlet

most photons that are productively absorbed in the chloroplast are absorbed by chlorophyll molecules in what type of complex?

antenna complex

what is the step/process in the light reaction with which atrazine interferes? how does it interfere?

blocks electron transport from photosystem 2 by binding to the plastoquinone binding site

where do the electrons come from in the electron transfer process?

come from water

of the different types of radiation, which is the highest energy?

gamma ray (short wavelength=more energy)

rank the following types of electromagnetic radiation from shortest to longest wavelength: red light, green light, ultraviolet, infrared, microwave, x-ray, blue light, and gamma rays

gamma rays, x-ray, ultraviolet, blue light, green light, red light, infrared, and microwave

what color light does chlorophyll not absorb?

green is not absorbed

what general structural/electronic characteristic is shared by organic compounds that absorb visible light?

have extensive systems of conjugated double bonds

list five different mechanisms by which an excited electron can return to a ground state configuration

heat, fluorescence, chemical work, energy transfer, phosphorescence

of the different types of radiation, which is the lowest energy?

microwave (long wavelength=less energy)

what is an exciton?

photon equivalent brought to the reaction center by its antenna complex

what is the longest wavelength of light that can be used by photosystem 1 and 2?

photosystem 1: 700nm photosystem 2: 680nm

which photosynthetic integral membrane protein complexes use energy from light?

photosystem 2 and 1

what are the three photosynthetic integral membrane protein complexes that support electron transport from water to NADPH?

photosystem 2 to cytochrome b6/f complex to photosystem 1

what does ATP synthase use to drive ATP synthesis?

proton gradient

what two colors of visible light absorbed by chlorophyll?

red and blue

what is the step/process in the light reactions with which paraquat interferes? how does it interfere?

short circuits photosystem 1, causing a release of superoxide in the light

why are quinones so important in biological oxidation/reduction reactions?

they are important redox intermediates because they are able to transfer up to 2 electrons at a time

where do the electrons end up in the electron transfer process?

they end up on NADPH. electrons are then transferred from NADPH to reduced forms or carbon in the dark reactions

how do the photosynthetic integral membrane protein complexes provide energy for ATP synthesis?

they form a proton gradient across the thylakoid membrane

what do the two compounds that are products of the first set do?

used to reduce carbon dioxide ATP: energy source NADPH: reducing agent that adds high energy electrons to form sugar