photosynthesis Flashcards
define autotroph
org that produces food on its own using photos thesis or chemosynthesis
define heterotroph
orgs that eat other orgs for protein and energy
define photoautotroph
orgs that get energy form light
what are the primary producers on earth
photoautotrophs
what is an organic mlcl
having one or more c-h bond
what is another term for carbon fixation
reduction rxn
what is the main process of the light rxn
the production of tap and nadph in the thylakoid membrane
where do the e- needed to change nadp+ to nadph come from?
the oxidation of H2O
what is the main process of the Calvin cycle
the consumption of tap and nadph in the stroma
define carbon fixation
the reduction rxn as CO2 (g) is fixed into a carbohydrate (s)
what 2 basic particulates are used to convert tap into a carb
- e- and p carried by Nadph
E of tap hydrolysis
define the photosynthetic apparatus
a series of larger protein complexes imbedded in the thylakoid membrane that are responsible for light rxns
define photosystem
a large complex where the light absorbing pigments for photosynthesis are organized with proteins and other molecules
where does the Calvin cycle occur?
in the stroma
define photon
contain fixed amounts of energy that are inversely related to wavelength
how to plants capture photons
using pigment mlcls; chlorophylls or carotenoids
how many wavelengths can chlorophylls absorb?
2, chlorophyl a absorbs red and chlorophyll b absorbs high blue
what are 3 possible outcomes of excited-state e- absorption within a pigment mlcl?
- e- returns to its ground state by emitting a class energetic photon or heat E
- e- returns to ground state as E is transferred to another pigment mlcl
- e- is transferred to an e- acceptor
define spectrophotometer
an instrument used to determine wavelengths of light absorbed by pigments like chlorophyll a, which produces an absorption spectrum
what is an absorption spectrum
a curve representing the amount of light absorbed at each wavelength
how is an action spectrum determined
by measuring the amount of O2 released by photosynthesis at Dif wavelengths of visible light
what two light trapping components are involved in photosynthetic electron transport
photosystem I and photosystem II
what are the steps of light rxns
- photon of light enters photosystem
- photon hits antenna
- pigment mlcls transfer E down antenna
- special chlorophyll a mlcl excites e- and causes it to move towards an e- acceptor
- absored light is converted to chem E when an excited e- from chlorophyll is transferred to a primary acceptor
- high E e- pased through the e- transport system
- p motive force is genrated and can be used for ATP synthesis
what is the structure of the photosstem
pigment mlcls bound to specific proteins within thylakoid membrane, organized to create photosystems
what is the antenna complex
sites where light is absorbed and converted into them energy during photosynthesis
what is another term for the antenna complex
light harvesting complex
what is the function of the photosystem
to trap photons of light and use that E to oxidize a rxn centre chlorophyll
what is photosystem I
p700, uses sunlight to make NADPH
what is photosystem II
p680, uses sunlight to make ATP
what happens to the e- lost in photosystem II?
photosystem I replaces it
what’s an example of where oxidation-reduction reactions occur?
in the cytochrome complex
describe the passage of e- through the thylakoid membrane s
- e- flow from PS II to cytochrome complex
- e- flow from cytochrome complex to PS I by protein plastocyanin
- e- from PS I donated to the protein ferredoxin
- ferredoxin donates e- to NADP+ reductase ( on stomata side)
- enzyme then reduces NADP+ to NADPH
how does the enzyme NADP+ reductase reduce NADP+ to NADPH
using 2e- from the electron transport system and one proton from the surrounding environment of the stromata
How do chlorophyll mlcls give up e- if photosystems are not easily oxidized?
through the absorption of photons of light by raising P680 to a higher e- state
in light rxns, how is ATP generated?
by Chemiosmosis
define photophosphorylation
The synthesis of ATP coupled to the transfer of electrons energized by photons of light.
how many photons of light does the photosynthetic apparatus need to absorb in order to get 4 e- from photosystem II to NADP+
8 photons of light (4 by each photosystem)
what is cyclic e- transport?
an e- transport system that produces only ATP by shutting down PS II
What is E used for in cyclic e- transport?
to establish a proton motive force to generate ATP
why does the cell shut down photosystem II?
to reduce the amount of NADPH being produced by the cell bc reduction of CO2 requires more ATP than NADPH
what is the Calvin cycle
The second stage of photosynthesis, in which electrons are used as a source of energy to convert inorganic CO2 to an organic form
what is another term for light independent rxns
the Calvin cycle
where does the Calvin cycle occur?
in the stroma of the chloroplast
is the Calvin cycle endogenic or exogonic
endogenic, it uses ATP
how many turns does the Calvin cycle take to make one sugar unit
3 to create 1 G3P
what is rubisco
an enzyme used to seperate C from CO2 and join it to RuBP
what are the stage of the Calvin cycle
fixation reduction and regeneration
what is fixation
the first step off the Calvin cycle, one C from CO2 is incorporated into 1 mlcl of RuBP per turn to produce 2 mlcls fo 3-phosphoglycerate
what is reduction
the second stage of the Calvin cycle, each 3-phosphoglycerate gains an additional P from breakdown of ATP, 2 mlcls of 1,3-biphosphoglycerate produced, each mlcl is reduced by e- from NADPH and one mlcl of G3P is created
what is regeneration
the third step of the Calvin cycle, per one cycle 2 mlcls of G3P are produced, making 6 C atoms, 5 of these C are used to regenerate rubisco for the next cycle
how much NADPH and ATP does the Calvin cycle require per one round
9 atp and 6 nadph
what is photorespiration
a process that metabolizes a by-product of photosynthesis
what occurs to the by product during photorespiration
it is moved out of the chloroplast using ATP
what are some solutions to photorespiration
CO2 pumps for aquatic plants, C4 CO2 shuttle for terrestrial plants, Cam pathways for desert plants
how much tap and nadph does the Calvin cycle need to make one glucose
18 Atp and 12 nadph
what mechanism do aquatic plants use to counteract photorespriation
CO2 pumps
where is HCO3- converted to CO2 in aquatic plants that use a CO2 pump
in the cytosol
what enzyme converts HCO3- to CO2 during CO2 pumping of aquatic plants
carbonic anhydrase
how are stages of the C4 pathway separated?
sectionally
how are the stages of the CAM pathway separated
temporally
in the CAM pathway, what processes are used during the day vs the night?
the Calvin cycle used during the day, the CAM pathway used during the night
define Crassulacean Acid Metabolism (CAM)
a biochemical variation of photosynthesis where CO2
what mlcl is accumulated during night for the CAM temporal pathway to use during the day
malate
what mlcl is oxidized during the day to be used during the night cycle of the CAM temporal pathway
malate
describe what happens during the night stage of CAM temporal seperation
malate accumulates and in stored in the cell vacuole
describe what happens during the day stage of CAM temporal seperation
the stomata closes off to store water and malate is oxidized to release CO2 inside of the chloroplasts
how is photorespiration minimized in CAM temporal seperation
Bc of high amounts of CO2 from the C4 pathway and low O2, photorespiration is minimized
what is the relationship of O2 to CO2 in C4 and CAM plants
it is a competitive inhibitor
