5.1 Photosynthesis and respiration Flashcards
what is the equation for photosynthesis?
6CO2 + 6H2O = C6H12O6 + 6O2
name the two stages of photosynthesis
- light dependent reaction
- light independent reaction
where does the light dependent stage of photosynthesis take place?
the thylakoid membrane
where does the light independent stage of photosynthesis take place?
the stroma
what are the products of light dependent reactions?
ATP, NADPH (reduced NADP), O2
name the two uses of light energy in the light dependent stage of photosynthesis
- photophosphorylation: adding an inorganic phosphate ion to ADP to make ATP
- photolysis: splitting water into H+ ions and OH- ions
define photophosphorylation
using light energy to add phosphate to a molecule
define photolysis
using light energy to split a molecule
define photoionisation
using light energy to to ionise an atom or molecule
define electrochemical gradient
a concentration gradient of ions
define oxidation
gain of oxygen, loss of electron or hydrogen
define reduction
gain of electrons or hydrogen, loss of oxygen
define chemiosmosis
the process of electrons flowing down the electron transport chain and creating an electrochemical gradient which drives ATP synthesis
what products are released through non-cyclic photophosphorylation?
ATP, NADPH and oxygen
what products are released through cyclic photophosphorylation?
ATP
which photosystem is used first in non-cyclic photophosphorylation?
photosystem 2
what wavelength of light does photosystem 2 absorb?
P680
what wavelength of light does photosystem 1 absorb?
P700
describe the process of cyclic photophosphorylation
excited electrons in photosystem 1 are released to electron carriers, which pass them straight back to photosystem 1, meaning the only product is ATP
describe 4 differences between cyclic and non-cyclic photophosphorylation
- photosystems 1 and 2 are used in non-cyclic, whilst only PS1 is used in cyclic
- photolysis of water is only required in non-cyclic, not cyclic
- NADPH is only synthesised in non-cyclic, not cyclic
- non-cyclic produces ATP, NADPH and oxygen, whereas cyclic only produces ATP
describe the process of light dependent reactions in photosynthesis [5]
- light absorbed by chlorophyll excites electrons
- electrons move out of chlorophyll molecule and along electron transfer chain, releasing energy
- light energy is used for photophosphorylation to join ADP and Pi to form ATP
- photolysis of water produces protons, electrons and oxygen
- NADP is reduced when electrons and hydrogen join, becoming NADPH
describe what happens during photoionisation in the light dependent reaction [2]
- chlorophyll absorbs light and excites electrons
- excited electrons are lost and chlorophyll become positively charged
suggest and explain the advantage of having different coloured pigments in leaves [1]
absorbs different wavelengths of light for photosynthesis
suggest two reasons why most of the light that falls on producers is not used in photosynthesis
- light is reflected
- light is wrong wavelength
name the two products of the light-dependent reaction that are required for the light-independent reaction
- ATP
- reduced NADP (NADPH)
explain how a reduced transfer of electrons down the chain reduces the rate of photosynthesis [4]
- reduced transfer of electrons leads to a reduced transfer of of protons across the thylakoid membrane
- so less ATP is produced
- and less NADPH is produced
- so light-independent reaction slows
what wavelength of light does photosystem II absorb?
680nm
what wavelength of light does photosystem I absorb?
700nm
name five differences between the processes of cyclic and non-cyclic photophosphorylation
- in cyclic, only PSI is involved, whereas in non-cyclic, both PSI and PSII are involved
- photolysis is only required in non-cyclic
- oxygen is only produced in non-cyclic
- NADPH is only synthesised in non-cyclic
- ATP produced in cyclic is used by the cell, whereas ATP produced in non-cyclic is used for the light-independent reactions
explain part 1 of the Calvin cycle
ribulose bisphosphate reacts with CO2 to produce two glycerate 3-phosphate molecules. the reaction is catalysed by rubisco enzymes
what enzyme catalyses the reaction between ribulose bisphosphate and CO2?
rubisco
what products are produced when ribulose bisphosphate and CO2 react?
two glycerate 3-phosphate molecules
explain part 2 of the Calvin cycle
glycerate 3-phosphate molecules are reduced to triose phosphate. hydrolysis of ATP provides energy for reaction. reduced NADP provides H+ ions for the reaction.
explain part 3 of the Calvin cycle
triose phosphate is used to regenerate ribulose bisphosphate or make hexose sugars. hydrolysis of ATP provides energy for this reaction
how many turns of the Calvin cycle does it take to make one hexose sugar?
6
how many carbon atoms are in a ribulose bisphosphate molecule?
5
how many carbon atoms are in each glycerate 3-phosphate molecule?
3
how many carbon atoms are in each triose phosphate molecule?
3
how many ATP molecules are hydrolysed in one turn of the Calvin cycle?
3
how many NADPH molecules are used in one turn of the Calvin cycle?
2
