photosynthesis

Question 1

Name two different polysaccharides that can be synthesised from the end products of the light-independent stage of photosynthesis.

Answer 1

starch / amylose / amylopectin
and
cellulose ;

Question 2

Explain what is meant by the terms autotroph and heterotroph. (2)

Answer 2

autotroph can make ,
organic molecule(s) / named organic molecule(s) ,
from , inorganic molecule(s) / carbon dioxide ;

heterotroph
relies on / needs to use / has to obtain /
feeds on and digests ,
(named) organic molecules (that have been made
by another organism) ;

Question 3

Describe how light is harvested in the chloroplast membranes (5)

Answer 3

(primary & accessory) pigments , are in / form a(n) ,
photosystem / complex / antenna complex ;

photon / light energy , absorbed by pigment (molecule(s)) ;

electron , excited / moves to higher energy level / delocalised , and returned to pigment ;

energy / photon) passed from one pigment to another ;

(energy / photon) passed to reaction centre / chlorophyll a /
PSI / PSII / primary pigment ;

range of / accessory , pigments allow range of wavelengths to be absorbed ;

Question 4

Triazine herbicide acts on the weeds by binding to a specific protein associated with photosystem II, blocking the movement of electrons between electron carriers.

Explain the effect that the herbicide binding to this protein will have on photosynthesis (2)

Answer 4

prevents non-cyclic photophosphorylation ;

no electron(s) available to form reduced NADP ;

ATP production by cyclic photophosphorylation is not prevented ;
no / less , ATP and no reduced NADP available for Calvin cycle / light independent reaction / conversion of GP to TP ;

Question 5

Plants treated with triazine herbicide can, when illuminated under experimental conditions, be seen to fluoresce (emit light) and give off small quantities of heat.
Suggest how this experimental finding could be explained (1)

Answer 5

energy given off from ,

high energy / excited , electron

Question 6

Paraquat is a weedkiller. It binds with electrons in photosystem I.
Suggest how paraquat results in the death of a plant (2)

Answer 6

prevents photophosphorylation ;
cyclic and non-cyclic ;
no / less , ATP / reduced NADP , for light-independent stage / Calvin cycle / GP to TP ;
no (named) substrate made for respiration ;