Photosynthesis Flashcards
what do all cell activities require?
energy
what happens in photosynthesis?
green plants use sunlight energy to make carbohydrates
plants that photosynthesise
autotrophs
what traps sunlight?
chlorophyll
what is needed in p?
co2 and water (light energy)
products of p?
glucose and oxyegn
equation for photosynthesis
6CO2 + 6H2O + light energy -> C6H12O6 + 6O2
3 roles of photosynthesis
plants get food directly for energy
other organisms get food by eating plants
all organisms get O2 for respiration
where does photosynthesis occur?
in any green part of the plant but mainly in the leaves
4 ways in which leaves are adapted for photosynthesis
large surface area/thin
large number of chloroplasts with chlorophyll
stomata to allow gas to diffuse in and out of the leaf
air spaces for diffusion of gases inside the leaf
what part of light can be used by plants
visible/white light only
how could you increase photosynthesis using light
electric light given in green houses
2 ways in which plants may get CO2
from plant respiration
from the atmosphere and respiration in living organisms and the combustion of fossil fuels
How do plants get water
It is absorbed from soil by root epidermal cells and moves up via the xylem to the leaves
2 stages of photosynthesis
light and dark stage
what does the light stage require
light (light dependent stage)
where does the light stage take place?
in the granum of the chloroplast
what does the dark stage not require?
light (non light dependent stage)
what is the dark stage dependent on?
the products of the light stage
where does the dark stage occur?
in the stroma of the chloroplast
which bit of the chloroplast is the granum
the layered bits
which bit of the chloroplast is the stroma
the cytoplasmy bit
products of the light stage
ATP and NADH
O2
role of ATP and NADH in the dark stage
these energy rich molecules are used in the dark stage to make glucose
role of O2 in the plant
used in plant respiration or released from the plant and used in respiration in other organisms
what is chlorophyll?
the green pigment found in chloroplasts in plants
what mineral is found in chlorophyll?
magnesium
what absorbs white light
chlorophyll (and other pigments)
what colours do plant pigments absorb from visible light?
all colours except green
what happens to green light?
it is reflected
what happens to the light energy absorbed?
energy is transferred to electrons making them high energy electrons
what happens to the high energy electrons
they are released from chlorophyll and passed along 2 pathways called cyclic and non-cyclic electron flow
Role of water in photosynthesis
In the light stage, water is split into H+ ions, electrons and oxygen
equation for when water is split into H+ ions, electrons and oxygen
H2O -> 2H+ +2e- + O2
role of NADP+ in photosynthesis
NADP+ picks up and carries high energy electrons and hydrogen ions
equation for when NADP+ picks up and carries high energy electrons and hydrogen ions
NADP+ +2e- + H+ -> NADPH
where do the electrons and H+ ions come from that NADP+ picks up
electrons come from chlorophyl and the hydrogen ions come from the splitting of water in the light stage
what happens to the electrons and H+ ions come from that NADP+ picks up during the dark stage
the electrons and H+ ions are released from NADPH and used to make glucose
first thing that occurs in cyclic electron flow
sunlight energy is absorbed by chlorophyll
cyclic electron flow: after sunlight energy absorbed
energised electrons are released from chlorophyll and picked up by an electron acceptor
cyclic electron flow: energised electrons are released from chlorophyll and picked up by an electron acceptor
the electrons are then passed along a chain of electron carriers
cyclic electron flow: what happens along the chain of electron carriers
energy is released from the electrons and used to make ATP
cyclic electron flow: after energy is released from the electrons and used to make ATP
electrons return to the same chlorophyll
what is different about non-cyclic electron flow?
electrons do not return to the same chlorophyll
non-cyclic electron flow: first step
light energy is absorbed by chlorophyll
non-cyclic electron flow: after light energy is absorbed by chlorophyll
energised electrons are released and picked up by an electron acceptor
non-cyclic electron flow: after energised electrons are released and picked up by an electron acceptor
the electrons are then passed along a chain of electron carriers
non-cyclic electron flow: what happens along the chain of electron carriers
energy is released from the electrons and used to make ATP
non-cyclic electron flow: after energy is released from the electrons and used to make ATP
the electrons go on to combine with NADP+ forming NADP-
non-cyclic electron flow: after NADP- is formed
H2O is split into protons (H+), electrons and oxygen gas
non-cyclic electron flow: what happens to the protons from H2O
they go to a pool of protons in the chloroplast
non-cyclic electron flow: what happens to one of the protons?
it combines with NADP- forming NADPH
non-cyclic electron flow: equation form when proton combines with NADP- forming NADPH
NADP- + H+ -> NADPH
non-cyclic electron flow: where do the electrons from H2O go to
to the chlorophyll to replace the electrons that it lost
non-cyclic electron flow: what happens to the oxygen
used in plant respiration or released into the atmosphere
dark stage: what is used to make what and how?
CO2 entres a cycle called the calvin cycle and is used to make glucose
what controls the dark stage
enzymes
why is it significant that the dark stage is controlled by enzymes?
it is affected by temperature
2 sources of CO2
plant respiration
from the air (respiration of other animals/combustion)
dark stage: what does ATP supply
energy
dark stage: what does NADPH supply?
electrons and protons to converts into glucose
equation for dark stage
CO2 + NADPH + ATP -> Cx(H2O)Y + NADP+ + ADP + P
what is reused from the dark stage
NADP+ , ADP and P are reused in the light stage
3 major environmental factors that influence the rate of photosynthesis
light intensity
CO2 concentration
temperature
Elodea
pondweed
why is elodea used in experiments to measure the rate of photosynthesis?
it gives off oxygen bubbles that can be seen and counted
how do you measure the rate of photosynthesis
counting the number of bubbles of O2 released per minute
To investigate the influence of light intensity on the rate of photosynthesis: what is kept constant
the temperature and CO2 concentration
To investigate the influence of light intensity on the rate of photosynthesis: prepare the elodea
obtain a fresh shoot of Elodea and cut the stem at an angle
To investigate the influence of light intensity on the rate of photosynthesis: what do you do with the prepared Elodea
put it in a test tube of water containing excess sodium hydrogen carbonate
To investigate the influence of light intensity on the rate of photosynthesis: purpose of sodium hydrogen carbonate
to keep the CO2 constant
To investigate the influence of light intensity on the rate of photosynthesis: where does the test tube go and why?
in a water bath to keep the temperature constant
To investigate the influence of light intensity on the rate of photosynthesis: how far away from the light
a measured distance e.g. 15cm
To investigate the influence of light intensity on the rate of photosynthesis: when do you start counting and why
5 minutes after to allow the plant time to adjust to the light intensity
To investigate the influence of light intensity on the rate of photosynthesis: what do you count
the number of O2 bubbles released per minute
do it 3 times and get an average. record result
To investigate the influence of light intensity on the rate of photosynthesis: how do you vary the light intensity
place the plant at different distances from the lamp (allow time to adjust each time)
To investigate the influence of light intensity on the rate of photosynthesis: how do you measure the light intensity at each distance
using a light meter
To investigate the influence of light intensity on the rate of photosynthesis: x axis and y axis
x-axis: rate of photosynthesis
y-axis: light intensity
what limits the rate of photosynthesis
the factor which is nearest its minimum value
