photosynthesis & respiration Flashcards
look at cycles and diagrams also
reduction =
(biology version)
gain of electrons & gain of H2
which organelle does photosynthesis occur in?
chloroplast
thylakoid =
folded membrane containing chlorophyll
grana =
stack of thylakoids
which part of the chloroplast does the ‘light-dependant’ reaction occur in?
thylakoid membranes
summary of ‘light-dependant’ reaction
light energy & H2O used to prod. reduced NADP & ATP
(NADP –> P for photosynthesis)
the 4 stages of the ‘light-dependant’ reaction
- photolysis
- photoionisation
- photophosphorylation
- chemiosmosis
‘photolysis’
- the breaking down of H2O molecules, using light energy
- prod H+ & e-
- O2 formed (waste product)
‘photoionisation’
- light energy absorbed by chlorophyll
- excites electrons to higher energy level
- electrons emitted from chlorophyll
- leaves +vely charged chorophyll ion
‘photophosphorylisation’
- excited electrons passed along electron transfer chain, releasing energy
- electron carriers reduced then oxidised (gain then lose elc)
- excited elc gradually loses energy when passed along chain
‘chemiosmosis’
- the energy released by the excited elc moving down the etc. actively transports H+ protons from the stroma –> thylakoid lumen
- electrochemical gradient created
- the H+ protons return to stroma via faciliated diffusion, through ATP synthase
(process prov. energy needed to prod atp –> Pi added to ADP via ATP synthase)
the cycle for the ‘light-independant’ reaction is called…
the calvin cycle
which part of the chloroplast does the ‘light-independant’ reaction occur in?
the stroma
summary of the ‘light-independant’ reaction
reduced NADP used to prod. simple sugar
(energy prov. by hydrolysis of ATP)
describe the calvin cylcle (5)
- 5C RuBp (ribulose biphophate) **combines **with CO2
- prod. two 3C glycerate(-3)phosphate (GP), using ATP
- GP reduced to 3C TP (triose phosphate)
- using electrons from red. NADP & energy from ATP
- two molecules of TP = hexose
- all RuBp regenerated
facrors that affect the rate of photosynthesis
- intensity of light
- wavelength of light
why might chloroplasts absorb certain wavelengths of light better than others?
chloroplasts contain diff. photosynthetic pigments –> absorb diff. wavelengths
(chlorophyll A, chlorophyll B & carotenoids etc)
explain why CO2 is limiting for top leaves of trees
- light isn’t limiting –> rate of LDR is fast
- temp isn’t limiting –> fast reactions of enzymes in LDR
- high use of CO2 –> LDR is limiting
explain how O2 production shows photosynthesis
- O2 prod. in LDR
- faster O2 production = faster LDR
chromotography
explain why origin marked in pencil (2)
- ink & leaf pigments would mix
- pencil line remains in same position
chromatography
name 2 advantage of diff. pigments
- absorbs more wavelengths of light for photosynthesis
- more efficient photosynthesis if some wavelengths not present
which organelle does aerobic respiration occur in?
mitochondria
name the diff. stages of aerobic respiration
- glycolysis
- link reaction
- krebs cycle
- oxidative phosphorylation
which parts of the mitochondria do the diff. stages of aerobic resp. occur in?
- glycolysis –> cytoplasm
- link reaction –> matrix
- krebs cycle –> matrix
- oxidative phosphorylation –> inner membrane of mitochondrial cristae
‘glycolysis’
- phosphorylation of glucose using ATP
- oxidation of TP to pyruvate
- net gain of ATP
- NAD reduced
‘link reaction’
- pyruvate oxidised into acetate, losing H2 & prod. reduced NAD
- acetate combines w coenzymeA –> prod acetylcoenzymeA –> also releases CO2
- thus ‘oxidative decarboxylation’ occurs
(for every glucose molecule in glycolysis, LR occurs 2x as 2 pyruvates prod in glycolysis)
‘krebs cycle’
- a 4C molecule combines with 2C acetylcoA, forming 6C citrate which enters cycle & releasing coenzymeA
- oxidative decarboxylation of citrate –> CO2 lost & H2 removed to reduce coenzymes NAD n FAD
- ‘subtrate level phosphorylation’ occurs –> energy from dehydrogenation used to form ATP from ADP + Pi
- 4C molecule regenerated
‘oxidative phosphorylation’
- coenzymes donate H2 to one of the proteins
- H2 atoms split into protons & elc
- elc transferred down etc –> prov. energy for H+ protons to move into intermembrane space
- oxygen = final electron acceptor –> H2O formed
how is ATP prod in both photosynthesis & resp?
(chemiosmotic theory)
protons diffuse down an electrochemical gradient through ATP synthase enzyme, embedded in membranes of cellular organelles
explain why plants make ATP in both respiration & photosynthesis
- photosynthesis doesnt prod ATP in darkness
- ATP cannot be moved from cell to cell
- plant uses more ATP than prod. in photosynthesis eg for active transport
- so ATP must also prod via resp
state when NAD reduced in resp
- glycolysis
- LR
- krebs cycle
state when CO2 is made in resp
- LR
- krebs cycle
describe how acetylcoA formed
- H2 removed from pyruvate & CO2 released
- addition of coenzymeA
describe how ATP made in mitochondria
- ‘substrate level phosphorylation’
- krebs cycle & LR prod. coenzymeA, red NAD n FAD –> elc released
- electrons pass along etc
- protons move into intermembrane space
- energy released to join ADP + Pi –> ATP
- through ATP synthase
anaerobic resp
- no final electron acceptor
- no krebs cycle
- ATP can still be prod via glycolysis when NAD is oxidised
anaerobic resp
ethanol pathway
(used by yeast & microorganisms)
- pyruvate from glycolysis decarboxylated to ethanal
- ethanal reduced to ethanol via enzyme alcohol dehydrogenase
- ethanal = hydrogen acceptor (frrom oxidation of red NAD)
- ethanol CANNOT be metabolised
anaerobic resp
lactate pathway
(used by mammals)
- red NAD transfers its hydrogens to pyruvate to convert it to lactate
- pyruvate also reduced to lactate by enzyme lactate dehydrogenase
- pyruvate = hydrogen acceptor
- lactate CAN be further metabolised
advantage of converting lactate back into pyruvate
- pyruvate = energy source
- mucles have increased ATP supply
- restores pH levels
explain why coloured liquid moves into respirometer
- oxygen taken up in aerobic resp
- CO2 given out absorbed by KOH sol
- decrease in volume of gas
explain why respirometer is airtight
- no oxygen can enter
- no carbon dioxide can escape
- allows accurate measuring
- prevents entry of microorganisms
- prevents competition with yeast
suggest why respirometer left for 10 mins
- equilibrium reached
- allows resp rate to stabilise
how to get reliable results
- repeat to identify anomalies
- carry out statistical tests to ensure results are significant
