Photosynthesis Flashcards
what are photons
wave packets of electromagnetic radiation
what are the two steps of photosynthesis
light dependent and light independent reactions
where does light dependent reactions occur
thylakoid membrane
where does light independent reactions occur?
stroma
what are the three stages of light reactions
photo excitation
electron transport
chemiosmosis
what is photo excitiation
the first stage of light reactions
one of the chlorophyll’s electrons gets excited by a photon
what is electron tranpsort
the second stage of light reaction
along a series of carriers creating a hydrogen ion resevoir
what is chemiosmosis
protons move throughout ATP synthase to make ATP
where is starch stored
in roots and chloroplasts
what is photorespiration
the reaction of oxygen with rubisco in a process that reverses carbon fixation and reduces the efficiency of photosynthesis
(O2 takes the place of CO2, so that the calvin cycle cannot occur)
where does the calvin cycle occur
in the stroma
how is glucose formed through the calvin cycle
2G3P merge to form 1 glucose molecule
explain the steps in photoexcitation
- photon is absorbed into photosystem II
- it bounces around from pigment to pigment until it reaches chlorophyll a molecule
- an electron from the chlorophyll a gets excited and goes to the primary electron acceptor
- it pulls apart H2O to take the electron back, releasing O2
explain the steps of electron transport
- after the electrons are pulled apart, they get moved to the electron acceptor
- then transported to the electron carrier protein which brings it to B6-F complex
- the B6-F complex pushes out the H+ to form an electron gradient which is needed for chemiosmosis
- meanwhile the same stuff occurs in photosystem I except the electrons needed to balance the chlorophyll a comes from the electron carrier
- the NADP reductase norms NADPH
explain the steps of chemiosmosis
the electron gradient formed by the b6-f complex aids in the function of the ATP synthase, which pumps H+ through, turning ADP into ATP
what is different about C4 plants
they have seperate areas where O2 and CO2 reside
where do C4 plants typically grow
tropical areas where it’s always hot
what are the two cells in C4 plants and their order
mesophyll cell – where co2 enters and is converted to malate
bundle-sheath cell – where calvin cycle occurs
explain the difference process in C4 plants
- CO2 reacts with pop to form oxaloacetate
- oxaloacetate to malate (NADPH to NADP+)
- malate to CO2 and pyruvate
- pyrivate to pep (ATP to AMP)
where do CAM plants grow
tropical areas
hot days, cold nights
explain how CAM plants work
- they take in he CO2 overnight, when it’s not dangerous to have open stomata (lower risk of losing water)
- converts it to oxaloacetate and then malate to be stored
- in the day, when the sun is shining, the malate is converted back to CO2 to do the krebs cycle
what are autotrophs
self feeders
they sustain themselves without eating anything derived from other living beings
what are photoautotrophs
a type of autotrophs that use light for energy
what are heterotrophs
unable to make their own food; they live on compounds produced by other organisms
what role does colour play in plants
- the chloroplasts have that green tint, so anywhere where a plant is green is where they reside
- the chloroplasts also absorb light, w the exception of green light, which is what makes it have that colour
what is the photosynthesis equation
6 CO2 + 12 H2O + Light energy —» C6H12O6 + 6 O2 + 6 H2O
why do chloroplasts only absorb specific colours of light
they’re more effective in driving photosynthesis
typically take in red and violet-blue
reflect green light
explain cyclic electron flow and how it starts
- due to a lack of ATP, it is an easy conclusion that there is smth wrong w ATPase
- ATPase is based on the proton gradient formed by the cytochrome b6f complex
- instead of creating more NADPH through the NADP reductase, the electrons get carried back to the b6f complex to improve the gradient
anabolic reactions
uses energy- forming larger from smaller
catabolic reactions
give off energy- breaking apart larger to form smaller
what is carbon fixation
the initial incorporation of CO2 into organic molecules
why do C3 plants exist
it is believed that they are at an evolutionary disadvantage from when less )2 existed (less humans) and more CO2
what do plants do with glucose
used for making cellulose and starch
starch is a food source
cellulose is is used in building cell walls
what is the ideal temperature for C3 plants?
15-25 C
what is the ideal temp for C4 plants
30-40 C
what is the ideal temp for CAM plants
above 40C
how does the C4 plant combat photorespiration
performing carbon fixation and calvin cycle in different cells
how do CAM plants combat photorespiration
performing carbon fixation and calvin cycle at different times
what happens during day time for CAM plants?
- they keep their stomata closed during the day to minimize water loss
- when light reactions occur (because the sun is out) they form the necessary reactions to make atp and NADPH so that the calvin cycle can occur
what happens during the night for CAM plants?
they open their stomata to take in as much CO2 as possible and react w pep to form oxaloacetate to then form malate to be stored until the daytime (when light reactions occur)
how are C3, C4 and CAM photosynthesis similar
- all 3 are ways of making energy for the plants
- all 3 use the same light reactions and end up using the calvin cycle to form glucosoe
vaguely, how are C3, C4 and CAM different
have different modes of carbon fixation
different ways of combating photo respiration (or not combating it at all)(looking at you C3)
what are the initial carbon acceptors for C3, C4 and CAM plants
Pep is the initial acceptor for C4 and CAM
RuBP is the initial acceptor for C3
