Question 19M.2.SL.TZ1.c
| Date | May 2019 | Marks available | [Maximum mark: 7] | Reference code | 19M.2.SL.TZ1.c |
| Level | SL | Paper | 2 | Time zone | TZ1 |
| Command term | Explain | Question number | c | Adapted from | N/A |
Explain how plants capture and use light in photosynthesis.
[7]
a. plants convert light energy into chemical energy by photosynthesis ✔
b. photosynthesis takes place in chloroplasts ✔
c. chloroplasts «are organelles that» contain the pigment chlorophyll ✔
d. chloroplasts/chlorophyll «in plants» absorb sunlight ✔
e. «chlorophyll» absorbs red AND blue light most effectively ✔
f. light causes photolysis/splits water molecule ✔
g. carbon dioxide AND water are reactants «in photosynthesis» ✔
h. glucose AND oxygen are products «of photosynthesis» ✔
i. light intensity is a limiting factor for the rate of photosynthesis ✔
j. organic/carbon compounds/glucose provide food/stored energy «for plant itself, animals,food chains» ✔
k. up to one additional mark for an accurate detail from AHL ✔
Generally well done with some very knowledgeable answers from the Higher Level programme sometimes to the detriment of the more basic answers required by the standard level examination. Many candidates who attempted this response got more than 4 marks for mp b, d, g and h which were the most common. Students getting higher marks were able to focus on correct conversion of energy, efficiency of red and blue light absorption, and photolysis. Some egregious misconceptions exist among candidates such as plants are green because they absorb green light. The idea that during photosynthesis light energy is converted to chemical energy was frequently neglected.
