Lecture 15-16: Photosynthesis Flashcards
photosynthesis:
builds reduced molecules from CO2 and H2O (anabolic)
photosynthesis is done by?
photoautotrophs (the producers of the biosphere)
what kind of reaction is photosynthesis?
endergonic (requires energy from sunlight)
where does photosynthesis take place?
chloroplast
a typical mesophyll cell has how many chloroplasts?
30-40
what is fluid inside the chloroplast called?
stroma
where does the calvin cycle occur?
the stroma -> inside the chloroplast
how many layers does the membrane of the chloroplast have?
2
what is the third membrane system inside the chloroplast called?
thylakoids
how do thylakoids form grana?
by being stacked inside the chloroplast
what is the lumen?
the thylakoid intermembrane space, where light reactions occur
what is chlorophyll?
the pigment that absorbs and transforms photon energy
where is chlorophyll found?
the thylakoids
what do pigments absorb?
wavelengths of light
what happens when pigments don’t absorb wavelengths of light?
its reflected, giving off “colour”
why are plant leaves green?
they don’t absorb green light!
what is the absorption spectrum?
the pigments light absorption versus wavelength
what happens when a photon is absorbed by a molecule?
an electron is converted to a higher-energy state (excited state)
what happens when an excited electron falls back to ‘ground state’?
- energy can be dissipated as heat
- energy can be re-emitted in form of less energetic and longer wavelength photon called fluorescence
- energy can be transferred to another molecule
when will chlorophyll fluoresce?
when its isolated from the chloroplast because it isn’t organized by the chloroplast!
why does the chloroplast have many types of pigments?
allows it to absorb many different wavelengths of energy from sunlight
three main types of chlorophyll:
chlorophyll a
chlorophyll b
carotenoids
what are photosystems composed of?
reaction centre complex surrounded by many light-harvesting complexes
what chlorophyll molecules are in the reaction centre?
P680 and P700
(P: pigment, ###: wavelength absorbed best)
where does the reaction centre pass on electrons to?
primary electron acceptor
can photoexcited electrons bypass photosystem II into photosystem I?
sometimes! it’s like a short circuit
what is the advantage and disadvantages of photoexcited electrons skipping to photosystem I?
advantage: supplements ATP synthesis
disadvantage: no NADPH production and no O2
mitochondria and chloroplasts both utilise ______ to generate ATP
chemiosmosis
both the mitochondria and chloroplasts utilize chemiosmosis to pump H+ across a membrane from a region of ___ H+ to ____ H+
low -> high
where does photosyntheiss occur in a “normal” C3 plant
mesophyll cells
where does the gas exchange take place in a C3 plant?
the stromata
how do the sugars get transported in a C3 plant?
the veins of the leaf
chemical formula for photosynthesis:
energy + 6CO2 + 6H2O -> C6H12O6 + 6O2
C4 plants have extra cells called _____ associated with the veins
bundle sheaths
where does the calvin cycle occur in C4 plants?
only in the chloroplasts of the bundle sheaths
difference between C3 and C4 plants?
majority of plants are C3 (first carbon compound produced in photosynthesis has 3 carbons), C4 plants have adapted to be able to bind carbon dioxide when it enters the leaf and produce a 4-carbon compound
_____ are products of ancient photosynthesis
fossil fuels
