Topic 5 - energy for biological processes

Question 1

draw and label the parts of a chloroplast, explaining their function

Answer 1

stroma (fluid)> where ATP is used, converting carbon dioxide to glucose

granum> stacks of thylakoids

thylakoids> where chlorophyll captures energy from light and uses it to produce ATP

inner and outer membrane (envelope)

lamellae > join together stack of membranes called grana

Question 2

what are the two types of chlorophyll?

Which is the main pigment and which is an accessory?

Answer 2

chlorophyll A is the main pigment and chlorophyll B is the accessory pigment

Question 3

what are the two stages of photosynthesis? where do these stages occur?

Answer 3

light dependent reactions (happens on thylakoid membranes)

light independent reactions (happens in stroma)

Question 4

outline and explain the light dependent stage of photosynthesis

Answer 4

cyclic:
a photon of light hits chlorophyll molecule
electrons are excited (raise up energy levels)
electrons taken up by electron acceptor
electrons passed along ETC, energy is released and ATP is synthesised
electrons return to PSI

non-cyclic:
electrons hit chlorophyll in PSII , magnesium is reduced
Mg-> Mg2+ + 2e-
electrons are excited (go up energy levels)
can’t maintain this energy so they fall, releasing energy, and pumping H+ ions through thylakoid membrane
H+ ions travel through ADP synthase (ADP->ATP)
These H+ join with NADP to form NADPH

photolysis is continually happening in the stroma
2H2O-> 2H++2e-+o2
electrons replace magnesium’s lost electrons

Question 5

outline and explain the light independent stage of photosynthesis

Answer 5

calvin cycle

fixation:
RuBP (5 carbons) joins with CO2 to make 6 carbon compound, catalysed by RUBISCO
6 carbon splits into 2X 3 carbon molecules of GP

reduction:
ATP reduced back to ADP + Pi
ADPH oxidised to make NADP
causes GP to be reduced and phosphorylated into GALP
(pi which has come from ADP joins onto GP, making GALP)

regeneration:
regenerated back to RuBP
1 carbon taken to make glucose, other 5 taken back into cycle

(takes 6 turns of the cycle to make glucose)

Question 6

what molecule is produced by photophosphorylation?

Answer 6

ATP

Question 7

where does carbon fixation take place in a chloroplast?

Answer 7

stroma

Question 8

explain why the light-independent stage can’t happen without tight dependent stage.

Answer 8

light dependent stage produces products needed

ATP- provides energy

NADPH- used for reduction of carbon dioxide/GP

Question 9

what are photoreceptors in plants used for and what are they affected by?

Answer 9

photoreceptors are used in plant growth and development.
they are affected by darkness.