L5 - photosynthesis Flashcards
what is the energy flow of photosynthesis?
light captured by chloroplast, water and carbon dioxide is converted into carbohydrates, oxygen becomes a by-product, the mitochondria breaks down carbohydrates, and chemical energy is released and stored and as ATP
what is the first intermediate of photosynthesis?
a triose sugar (3-carbon)
how many molecules of water is needed to convert three molecules of carbon dioxide into a triose sugar?
6
what is the end produce of photosynthesis?
glucose (6-carbon sugar)
what is anoxygenic photosynthesis?
photosynthesis using hydrogen sulfide instead of stripping electrons off water
in anoxygenic photosynthesis, what is produced instead of oxygen within the cell?
sulfur
how was energy produced before photosynthesis?
all energy on the planet was essentially conserved - the atmosphere was mostly nitrogen
what happened after photosynthesis began?
there was an endless supply of solar energy, oxygen was being produced as a by-product which allowed for the creation of biomass
what organism first began using photosynthesis?
cyanobacteria - capable of splitting water into hydrogen and oxygen
what are the closest relatives of cyanobacteria?
Melainabacteria and Sericytochromatia (cannot photosynthesize)
what is the evolution of photosynthesis?
it had evolved once in Chloroflexus, and was transferred between distant lineage - no common ancestral pathway
how was the ability to photosynthesize in bacteria passed on?
horizontal gene transfer
what is the summary of photosynthesis evolution?
evolution of oxygenic photosynthesis likely happened several times however, origin is probably of one source. HGT spread capability to distant bacterial lineages and cyanobacteria was the precursor to chloroplasts and photosynthesis in plants
plants are ___ autotrophs
photo autotrophs
what are chemotrophs?
obtain energy by oxidation of electron donors in their environments, using Fe2+ as an electron donor and radiant energy to assimilate CO2 into biomass
short rays = …
more energy
what is the photoelectric effect?
light energy dislodges electrons from metal atoms - in other words, it is the emission of electrons from a material when light hits
what is the color we see in terms of wavelength when we look at plants?
we see the color that is reflected off the plant, i.e., what is not absorbed by the pigment
what is the significance of the color absorbed?
its the light energy being captured by plant systems
what is the action spectrum?
the effectiveness of different wavelengths for a specific process
what happens when chlorophyll absorbs light?
electrons boosted to higher energy, putting them in the excited state
how do electrons release energy?
- heat and fluorescence
- resonance energy transfer
- electron transport chain
where does chlorophyll a occur?
in all photosynthetic eukaryotes and cyanobacteria
significance of chlorophyll a
essential for photosynthesis, the primary pigment
what is the accessory pigment that plants and algae also have?
chlorophyll b
what are carotenoids?
accessory pigments, like chlorophyll b
found in all chloroplasts and cyanobacteria
appears red, orange, or yellow
lipid soluble pigments
what are the two types of carotenoids?
carotene and xanthophyll
who produces carotenoids?
only plants
what is beta-carotene?
the principal source of vitamin A in animals - a kind of carotenoid
how are carotenoids protective?
they protect chlorophyll from photodamage
what are phycobiliproteins?
an accessory pigment found in cyanobacteria and red algae.
They can absorb red, orange, yellow, and green light.
Transfer energy to chlorphyll.
Are classified as water-soluble proteins.
bound to phycobilin, a pigment/chromophore
what organisms are phycobiliproteins mnainly necessary for?
organisms living in deeper marine environments
why are several pigments used?
pigments allow complementary roles and modulate over seasons
what is the difference between carotenoids and phycobilins?
carotenoids are in the blue-green range and phycobillins are in the red-to-green range
what are the two stages photosynthesis occurs in?
light-dependent and carbon-fixation
water is oxidized, donates electrons
carbon is reduced, gains electron
