| Date | May 2013 | Marks available | 8 | Reference code | 13M.2.HL.TZ1.5 |
| Level | Higher level | Paper | Paper 2 | Time zone | Time zone 1 |
| Command term | Explain | Question number | 5 | Adapted from | N/A |
Question
Outline the metabolic processes that occur in starchy seeds during germination.
Explain the light-independent processes of photosynthesis in plants.
Markscheme
Remember, up to TWO “quality of construction” marks per essay.
a. water absorbed by the seed / seed rehydrated;
b. water activates metabolism;
c. gibberellin synthesized/produced/secreted;
d. gibberellin stimulates the production of amylase;
e. amylase digests/hydrolyses starch to maltose;
f. maltose converted/hydrolysed to glucose (by maltase);
g. glucose used in aerobic respiration;
h. glucose used in synthesis/production of cellulose;
Remember, up to TWO “quality of construction” marks per essay.
a. occurs in stroma (of chloroplast);
b. energy/ATP and NADPH provided by the light-dependent reactions;
c. Calvin cycle;
d. carbon dioxide fixed to RuBP / carboxylation of RuBP/ribulose bisphosphate;
e. by RuBP carboxylase/rubisco;
f. forms unstable 6C compound / forms 6C compound which splits;
g. glycerate 3-phosphate (is produced by carbon fixation);
h. (glycerate phosphate) to triose phosphate/3C sugar by reduction/adding hydrogen;
i. using NADPH/reduced NADP;
j. triose phosphate/3C sugar converted to form hexose/glucose (phosphate);
k. most/5/6 of triose phosphate used for regeneration of RuBP;
l. ATP used to regenerate RUBP/convert glycerate 3-phosphate to triose phosphate;
Examiners report
Well prepared candidates gave thorough and high scoring accounts of metabolic processes that follow water uptake in geminating seeds.
This was another high scoring part of the question for stronger candidates. A few misread the question and wrote about light-dependent reactions. The use of the abbreviation GP is discouraged as it is ambiguous in accounts of the Calvin cycle.
