Question 19M.3.SL.TZ2.1d
| Date | May 2019 | Marks available | [Maximum mark: 1] | Reference code | 19M.3.SL.TZ2.1d |
| Level | SL | Paper | 3 | Time zone | TZ2 |
| Command term | State | Question number | d | 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.
State one technological improvement, other than enzymatic digestion, that led to the falsification of previous models to determine the current model of membrane structure.
[1]
a. scanning electronmicrography / SEM ✔
b. freeze fracture/etching ✔
c. X-ray diffraction
OR
crystallography ✔
d. fluorescent antibody / marker tagging ✔
Do not accept electron microscope
Accept description of process
Stating a technological improvement that led to the currently accepted model of the cell membrane proved more challenging and only the better candidates answered correctly.
