Photosynthesis (chapter 7) Flashcards
define autotroph
an organism that makes its own food (often through photosynthesis) i.e. plants, algae, and numerous bacteria
define heterotroph
an organism that cannot make its own organic food molecules. must consume or decompose other organisms and their organic food products
equation for photosynthesis
6 CO2+ 6 H20+light —-> glucose (C6H12O6) + 6 O2
what becomes of the CO2 by the end of photosynthesis
the C becomes fixed (reduced) in glucose (C6H12O6). the O goes into glucose
what becomes of the H2O by the end of photosynthesis
it is oxidized and is released as O2. the H’s go into glucose
how is the O2 gas produced in photosynthesis
by splitting the water
what are the two main parts of photosynthesis
light reactions and Calvin cycle
explain the processes of the light reaction (generally)
light energy is converted to split H2O into H+ and O2. the H+ is added to NADP+ making NADPH. also generates some ATP from ADP
where is does the light reaction take place
in the thylakoids
explain the process of the Calvin cycle (generally)
assembles sugars from CO2 and the energy-rich products from the light reaction through carbon fixation. after that it makes more sugars through reduction
where does the Calvin cycle take place
the stroma
how is light energy converted to the energy of excited electrons, and what are the roles of photosystem II, photosystem I, and chlorophyll in this process
pigment absorbs photons which excite the electrons in the pigment, these excited electrons are transferred to other pigment molecules, until it reaches a pair of special chlorophyll molecules that can pass the energy onto a neighboring molecule
how are pigments is involved in photosynthesis
the pigments absorb the visible light in the chloroplast. for example chlorophyll a is green because it can’t absorb green light as well
what is water’s role in light reactions
the water is oxidized and its H’s are passed from photosystem II to photosystem I to replace the electrons lost. O’s just become O2 and are released
what are the products of light reaction
ATP, NADPH, O2
how is ATP produced in the light reaction
in the stroma there is a low concentration of H+, while in the thylakoid space there is a high concentration of H+. this means there is a proton gradient. the electron transport chain (using the sun’s energy to fuel it) pumps the H+ against the gradient. photosystem I causes the photophosphorylation of NADP+ (NADP+ is the final electron acceptor). the force of the concentration gradient forces the H+ through ATP synthase, creating ATP with that energy
where are the high energy products of light reactions
in the stroma, so they can be used to fuel the Calvin cycle
describe the Calvin cycle
3 CO2 and 5 RuBP go through the protein rubisco to make 6 3-PGA. 6 ATP and 6 NADPH are oxidized to give enough energy so the 6 3-PGA become 6 G3P. 1 G3P leaves the Calvin cycle at its product. the rest are used to regenerate the store of RuBP
define carbon fixation
when C from the atmosphere is incorporated into organic compounds
how does photosynthesis moderate climate change
while a lot of CO2 that’s absorbed is just reemitted, a significant portion of it stays trapped in the plant. also biofuels could be used to make a cycle of CO2 (not introducing any new CO2 to environment like the burning of fossil fuels)
