5.2.1 Photosynthesis Flashcards
what type of energy is light energy transformed into
chemical energy
what is the chemical equation for photosynthesis
6CO2 + 6H20 = C6 H12 O6 + 6O2
define autotroph
organisms that can make organic molecules from inorganic molecules
define heterotroph
an organism that have to obtain molecules that have been made by another organism
where does most photosynthesis take place in plants
in the palisade mesophyll cells
describe the structure of a chloroplast
- it has a double membrane
- fluid filled stroma which contains enzymes (L.ID.R)
- thylakoids contain photosynthetic pigment(LDR) are stacked into grana
- oil droplets which contain lipids for fixing membranes
- intergranal lammella which link grana
- enzymes like ATPsynthase and rubisco
what three things do thylakoids contain
1) enzymes- atpsynthase and rubisco
2) phtosynthetic pigment- eg chlorophyll
3) electron carriers for electron transport
what are photosynthetic pigments arranged into
funnel shaped structures called photosystems and are held in place by proteins
what is a photosynthetic pigment
give an example
a substance that absorbs certain wavelengths of light and reflects others
eg chlorophyll A/B, Carotenoids…
describe accessory pigments
surround the reaction centre
include chlorophyll B and carotenoids
these transfer light to the primary pigment reaction centre
describe the pigment in the primary pigment reaction centre
chlorophyll A absorbs the light of wavelength 680-700nm and 450-480nm (blue light)
has magnesium group
what are the two types of chlorophyll and where are they found
P700- found in photosystem I, found mainly on intergranal lammella
P680- found in photosystem II, occurs in the grana
how do primary and accessory pigments work together in photosystems
1) light energy is absorbed by accessory pigment, causes electrons in pigment to be raised to a higher energy level and return to the pigment
2) energy is passed to another pigment and then to another
3) energy is passed to the primary pigment reaction centre
4) electrons are lost from primary pigment and given to electron transport chain for LDR
how is seaweed specialised
lower light intensity in sea, so only certain shorter wavelengths pass through
has special pigment to absorb these specific wavelengths
explain oxidation and reduction in terms of
oxygen
hydrogen
electrons
oxygen- OIG RIL
hydrogen- OIL RIG
electrons- OIL RIG
what is the hydrogen acceptor coenzyme used in respiration
NADP
what is the role of NADP
to carry hydrogen to the calvin cycle
define photophosphorylation
the making of ATP in the presence of light
where does the L.D.R take place
thylakoid
describe the process of non-cyclic photophosphorylation
1) light strikes PSII which excites 2 electrons, these pass down electron carriers
2) the electrons release energy that pumps H+ into the thylakoid space
3) PSII has an enzyme that in light performs photlysis of H20= 2H+ + 2e- + 1/2 O2
4) light strikes PSI and excites 2 electrons, these leave chlorophyll and pass down electron carriers, they are accepted by NADP
5) H+ flows down proton gradient by chemiosmosis through ATPsynthase enzyme, this potential energy creates ATP
6) the H+ along with 2e- join with NADP to form NADPH
where does the cyclic photophosphorlyation take place
in the thylakoid membrane
what do weedkillers do
binds to electrons in PSI
stopping photophosphorylation from taking place
so NADPH does not form
and ATP does not form
describe the process of cyclic photophosphorylation
1) light hits PSI and excites 2 electrons which leave the chlorophyll and pass down electron carriers
2) they then move back through the carriers and create ATP by action of H+ moving through ATPsynthase
.: this is cyclic photop… because the electrons are in a cycle
describe the process of the calvin cycle
1) enzyme rubisco fixes CO2 to RUBP to make a 6c molecule GP, this is unstable and breaks into TP
2) each GP has 3 carbons and this can be used for amino acids or it can be converted to TP
3) to convert GP into TP- ATP and NADPH from LDR is needed to provide the H to make TP
4) 5/6 of every molecule of TP made is converted back into RUBP which is given a phosphate from ATP ( which makes ADP) and the cycle continues
one out of every 6 molecules of TP is used to make what
glucose, fructose, sucrose, starch, cellulose, amino acids
dont need to remember all of them i reckon, maybe 3
what do these mean
RUBP
TP
GP
RUBP= ribulose bisphosphate
TP- triose phosphate
GP- glycerate 3-phosphate
name 3 limiting factors for photosynthesis
temperature
carbon dioxide conc
light intensity
how does temperature affect the rate of photosynthesis
increases the activity of enzymes- molecules have more kinetic energy
- light independent reaction in particular
- activity of rubisco
what do plants do when they undergo water stress
they close their stomata
this reduces the loss of water vapour by transpiration
what is the compensation rate
when the respiration rate equals the photosynthesis rate
the carbon dioxide produced in respiration equals carbon dioxide absorption in photosynthesis
how could u measure the rate of photosynthesis
- measure increase in oxygen concentration
- measure the volume of co2 used in a given time
what device can u use to measure the volume of oxygen produced
what do we need to know to use this
what is an issue with this
a photosynthometer
the diameter of the capillary tube
- not all 02 is collected some is used in respiration
what is a hydrogencarbonate indicator used for, what does this show
used to measure the co2 levels in aquatic systems, becomes orange/ yellow in increased co2 levels
-changes from red to purple in low co2 levels
why do levels of RUBP go up when co2 conc decreases
- less GP is produced as less CO2 for rubisco to fix
- ATP from L.D.R converts TP into RUBP regardless
how can we control photosynthesis
-temp controlled by heaters and a thermostat
-light wave length controlled if dark
-co2 controlled by burning fuel
water supply controlled
use of fertilisers and pesticides
