Photosynthesis Flashcards
One of the students read that ammonium hydroxide is an alkaline substance
Suggest how it can act as a weed killer (3)
- proteins in thylakoid membrane could denature
- proton gradient betw thylakoid space and stroma disrupted
- ATP can’t be prod. / NADP can’t be reduced
- LDR can’t prod carbon compounds
Summary of LDR
- Photolysis of water provides H+ and e-
- Photophosphorylation involves passage of e- along e- transport chain
- light energy hitting photosystems causes photoionisation
- ATP prod. by chemiosmosis
- NADP reduced
ATP and NADPH passed to LIR
Describe how plants use light energy during LDR (5)
light absorbed by chlorophyll molecule
* excites e-
* e- move along e- transfer chain releasing energy
* energy used to join ADP and Pi -> ATP
* photolysis of water prod. H+, e-, o2
* NADP reduced by H+ and e-
Describe how NADP is reduced in LDR (2)
NADP combines with
* e-
and H+
* from photolysis
Where does LIR / Calvin cycle take place?
stroma
Where does LDR take place?
thylakoid membranes of chloroplasts
Explain why radioactive C from the air is found within plant tissues (2)
- carbon fixation occurs
- atmospheric carbon converted into organic compounds
LIR summary:
- the LIR’s fix co2 from atmosphere, prod. carbon compunds for the plant
Calvin Cycle involves:
* conversion of RuBP into GP in a reaction that requires co2, catalysed by Rubisco
* conversion of GP into TP, using products of LDR
* recycling of RuBP from TP
* some of the TP converted itno other C compunds eg. glucose, sucrose starch, amino acids
In the LIR, co2 is convereted into organic substances. Describe how: (6)
- co2 combines with RuBP
- producing 2 GP
- gets reduced to 2 TP
- using reduced NADP
- using energy from ATP
- TP used to make hexose sugar
Heat stress decreases the LIR. Why (2)
carrier proteins of e- transport chain denatured
energy not produced
* ATP not produced
* NADP not reduced
no e- for NADP to pick up to be used in LIR
Why does lowering T have more effect on LIR than LDR? (2)
- LIR has enzymes involved
- lowers rate of enzyme reaction / fewer collisions
Why does crop yield reduce when Rubisco competitively inhibited by o2? (3)
- less GP produced
- less triose phosphate to form hexose sugars
- less RuBP regenerated
Full name of GP AND TP:
- glycerate 3-phosphate
- triose phosphate
Where does LIR take place?
stroma
What will happen to the amount of O2 produced if there is no Rubisco functioning? (9)
- reaction betw/ co2 and RuBP wouldn’t occur
- no GP reduced to TP
- so r.NADP can’t be converted back to NADP
- no NADP to accept e- from ETC
- so e- can’t move down ETC
- so chlorophyll can’t emit e- to ETC
- chlorophyll not oxidised so photolysis (of water) can’t occur
- so o2 not released
- so o2 decreases
