Date | November 2018 | Marks available | 2 | Reference code | 18N.2.SL.TZ0.2 |
Level | Standard level | Paper | Paper 2 | Time zone | TZ0 / no time zone |
Command term | Explain | Question number | 2 | Adapted from | N/A |
Question
Label the area where cellulose is found in the micrograph of a plant cell.
[Source: BIOPHOTO ASSOCIATES/Getty Images]
Cellulose is the most abundant organic polymer on Earth. Describe the structure of cellulose.
Outline one reason for humans being unable to digest cellulose.
Explain the advantages of having both lipid and carbohydrate as energy stores in the human body.
Markscheme
label placed anywhere along outside perimeter/cell wall of plant cell ✔
a. unbranched/straight chain of glucose molecules
OR
unbranched/straight-chain polysaccharide ✔
b. formed of beta glucose;
c. formed by condensation reactions/glycosidic bonds
OR
1, 4 linkage ✔
d. hydrogen bonds form between cellulose chains
e. form microfibrils ✔
Award marks to an accurate annotated diagram
Do not allow carbohydrate
humans lack cellulase/appropriate enzyme ✔
a. lipid is long-term energy storage
OR
carbohydrate is short-term energy storage/readily available ✔
b. lipids are insoluble, so easier to store
OR
carbohydrates/sugars are soluble, so easy to transport by blood ✔
c. lipids store more energy «per gram»
OR
lipids occupy less space «per energy/kJ» ✔
OWTTE