Exam 1 - Photosynthesis Light Reactions Flashcards
What is the overall equation for photosynthesis?
Energy + 6CO2 + 6H2O —> C6H12O6 + 6O2
What is reduced in photosynthesis, and what is oxidized?
CO2 is reduced and H2O is oxidized
What is the overall equation for respiration?
C6H12O6 + 6O2 —> 6CO2 + 6H2O + Energy
What is reduced in respiration, and what is oxidized?
O2 is reduced and C6H12O6 is oxidized
How are photosynthesis and respiration related?
photosynthesis reverses the direction of electron flow compared to respiration (and vice versa)
What is reduction?
the gaining of an electron/the reduction of charge
What is oxidation?
the losing of an electron/the raising of charge
What are the main products of the light reactions of photosynthesis?
ATP and NADPH
What substrates are used by the carbon reactions of photosynthesis?
ATP and NADPH
What steps of the light reactions occur in the thylakoids?
- split H2O and release O2
- reduce NADP+ to NADPH
- generate ATP from ADP and Pi by photophosphorylation
What energy conversion occurs in the thylakoids?
conversion of light energy into chemical energy
What steps of the carbon reactions occur in the stroma?
- formation of sugar from CO2
- use of ATP and reducing power of e- carried by NADPH
What is the first step of the Calvin cycle?
carbon fixation
Why are the light reactions and carbon reactions interdependent?
- light reactions produce ATP and NADPH, the substrates of the carbon reactions, from ADP and NADP+
- carbon reactions turn use ATP and NADPH and produce ADP and NADP+, which is needed by the light reactions
What is chlorophyll a?
the main photosynthetic pigment
What is the role of accessory pigments, such as chlorophyll b?
to broaden the spectrum of light used for photosynthesis
What is the role of carotenoids?
to absorb excessive light that would damage the chlorophyll
Why do we compare absorption and action spectra?
to determine if what is absorbing the light actually shows a response
What does a photosystem consist of?
a reaction-center complex surrounded by light-harvesting complexes
What is the role of light-harvesting complexes in photosystems?
transfer the energy of photons to the reaction center
What are the characteristics of photosystem II?
- functions first
- best at absorbing light at a wavelength of 680 nm
- reaction-center chlorophyll a is called P680
What are the characteristics of photosystem I?
- functions second
- best at absorbing light at a wavelength of 700 nm
- reaction-center chlorophyll a is called P700
What is the chloroplast coupling center of ATP synthase?
uses proton gradient across thylakoid membrane to synthesize ATP (couples ATP synthesis with the proton gradient)
Why is it important that P680 is a strong oxidant?
its “electron hole” must be filled, which greatly facilitates transfer of electrons from split water molecules
