Chapter 10 Flashcards
What is photosynthesis? What is the general reaction formula?
light energy captured and used to converted co2 into more complex carbon compounds.
6CO2 + 6H2O –> C6H12O6 + 6O2
Know the difference between autotrophs and heterotrophs
autotrophs –> use photosynthesis to make their own food
heterotrophs –> must consume other organisms to obtain food
Photosynthesis is a redox reaction
C atom in CO2 is in a oxidized state –> reduced to carbohydrates
O atom in H2O is in a reduced state –> oxidized to O2
What happens in non-oxygenic photosynthesis
other molecules donate protons and electrons
-purple sulfur bacteria –> uses H2S
-green sulfur bacteria –> uses sulfide ion, hydrogen, ferrous iron as electron donors
What happens in the light reactions v. the dark reactions (carbon-fixation)—you don’t
need to draw them step by step, but know generally what important thing happens in
each. (look at slides 11 and 12—bullet points and the processes in the figure that align
with each).
light reaction : light energy converted into chemical energy as ATP and NADPH
carbon-fixation reaction: uses ATP and NADPH plus CO2 and produces carbohydrates (sugar)
What part of the electromagnetic spectrum is visible light
400-700nm
What happens when photons of light bounce off, pass through, or are absorbed by
molecules.
Bounce off -> scattered or reflected
pass through –> transmitted
absorbed –> adding energy to molecule (excited state)
What are pigments? Which are the main pigments used by plants? What colors do
chlorophyll absorb and scatter?
pigments -> molecules that absorb specific wavelengths of visible light
main pigment in plants are chlorophyll A, the accessory pigments are chlorophyll B, carotenoids, phycobilins
chlorophyll absorbs red and blue and scatters green
Know how to understand and absorption spectrum (eg what is the graph at the top of
fig 10.5 showing)
Plot of wavelengths absorbed by a pigment.
What is a photosystem?
Has a hydrocarbon “tail” that anchors it in a protein complex in the thylakoid membrane called a photosystem(where pigments are anchored)
Light harvesting complex v. reaction center—what are their purposes/what do they do?
Eg How is light captured by plants?
Pigment molecules are arranged in light-harvesting complexes
Several complexes surround a reaction center in the photosystem
Photosystem I v. photosystem II—absorb at different wavelengths—why?
Photosystem I → absorbs best at 700 nm
Photosystem II → absorbs best at 680 nm
Where does CO2 fixation take place
stroma
What is the Calvin cycle? What are the major product(s)?
The CO2 fixation pathway is the calvin cycle
CO2 > 3PG > G3P > regeneration of RuBP (CO2 acceptor)
G3P is the major product
What/how is the calvin cycle stimulated?
Light-induced electron transport reduces disulfide bounds in calvin cycle enzymes to activate them, via ferredoxin and thioredoxin
