Question 19M.3.SL.TZ2.1c.i
| Date | May 2019 | Marks available | [Maximum mark: 1] | Reference code | 19M.3.SL.TZ2.1c.i |
| Level | SL | Paper | 3 | Time zone | TZ2 |
| Command term | Deduce | Question number | c.i | Adapted from | N/A |
Two models of plasma membrane structure are shown.
[Source: diagram from article published in The American Journal of Pathology, 65, J Singer and G Nicolson,
The structure and chemistry of mammalian cell membranes, 427–437, Copyright Elsevier (1971)]
Phospholipase C is an enzyme that digests the polar heads of phospholipids. Scientists used phospholipase C to test these models of membrane structure. They found that the enzyme could digest the heads of phospholipids in the plasma membranes of red blood cells.
Deduce one conclusion about the structure of the plasma membrane reached by the scientists from their results.
[1]
a. phospholipids on outside/exposed ✔
b. impossibility of continuous protein layer «of Davson–Danielli/model A» ✔
c. supports idea of mosaic pattern of membrane
OR
supports model B ✔
Award any other valid conclusion.
Do not accept "membrane is made of phospholipids".
Many candidates answered that the enzyme acted on the phospholipids but failed to make a deduction about the structure of the membrane.
