Photosynthesis Flashcards
What is the overall chemical equation for the process of photosynthesis?
6 CO2 + 6 water -> C6H12O6 + 6 O2
light energy oxidizes water to release oxygen and reduces carbon dioxide to form sugars
What key concepts of light are relevant to photosynthesis?
behaves as wave:
wavelength (distance between wave crests) determines colour, frequency (number of crests per unit time) determines energy level, electric and magnetic fields oscillate 90 degrees to each other
behaves as particle:
photons contain unit of energy (quantum), energy in light is not continuous, energy = Planck’s constant x frequency
sunlight is a collection of photons of various frequencies, we only see the visible spectrum, plants only use the absorption spectrum of chlorophyll a (400 and 700 nm)
What is the general composition of chlorophyll and how does this allow light energy to become trapped?
absorption of a photon by chlorophyll causes a transition to a higher-energy state (more energy from blue light than red light), which can do 4 things: re-emit photon (fluorescence), convert to heat, participate in energy transfer, or photochemistry (transfer directly to chemical reactions)
amphipathic structure with porphyrin ring (4 nitrogens coordinate 1 Mg) involved in electronic transition and redox and hydrocarbon tail that anchors to thylakoid membranes
chlorophyll a and b in green plants, c and d in protists and cyanobacteria
What is the function of accessory pigments and how are they identified?
carotenoids are linear molecules with conjugated double bonds, purpose is filling in gaps of absorption (400-500 nm) then transferring to chlorophylls, characteristic orange yellow colour
What is the difference between absorption and action spectrums?
action spectrum: shows response of a biological system to light as a function of wavelength
absorption spectrum: provides information on the amount of light energy absorbed by a compound as a function of wavelength
What is the general absorption spectra of chlorophyll and carotenoids?
chlorophyll: 400 and 700
carotenoids: 400 to 500
What is the reaction center?
some light energy absorbed by chl is stored as chemical bonds, pigments serve as antenna complex to collect and transfer energy to reaction centers
redox reactions using electron transfer leads to long-term energy storage
association of each reaction center with an antenna complex maintains activity
integral membrane proteins
How does the concept of quantum yield pertain to photosynthesis?
quantum yield: number of photochemical products per number of quanta absorbed (0 of process doesn’t respond to light, 1 if every absorbed photon contributes to process, actual yield is 0.95)
efficiency of chemical process is far less ie. percentage of absorbed light energy that actually performs photosynthetic reaction is about 25% (still remarkably high for any conversion system)
How does the concept of redox reactions relate to photosynthesis?
overall process is a redox reaction where electrons are moved from one species to another (many compounds serve as artificial electron acceptors in the Hill reaction) ex. NADPH oxidized to NADP+, then reduced back via light energy
oxygen evolution occurs in the absence of CO2, comes from water instead
What is the difference between the light and dark reactions?
What are the components of the Z scheme?
What is the anatomy of chloroplasts?
What is the difference between photosystems I and II?
What is the role of electron transport in the Hill reactions?
What is the role of carboxylation, reduction, and regeneration in the Calvin-Benson cycle?
