Date | November 2016 | Marks available | 3 | Reference code | 16N.2.HL.TZ0.2 |
Level | Higher level | Paper | Paper 2 | Time zone | TZ0 / no time zone |
Command term | Deduce, Label, and State | Question number | 2 | Adapted from | N/A |
Question
The image is an electron micrograph of the lining of the small intestine.
(i) Label the microvilli using the letter M and a nucleus using the letter N.
(ii) State the function of the goblet cell.
(iii) Deduce, with a reason, whether or not the goblet cell is likely to divide.
Explain how the cell cycle is controlled.
Markscheme
(i)
Award [1] for one microvillus labelled M and one nucleus labelled N.
Both are essential for the mark.
Do not award the mark if any structure is labelled incorrectly.
(ii)
secretion/exocytosis / produce mucous
Candidates are not required to have studied goblet cells, so are just expected to deduce from the vesicles that the function is secretion; allow enzyme secretion but reject answers suggesting secretion of something that is clearly incorrect such as secretion of bile.
(iii)
not likely to divide as specialized/differentiated
OR
not likely to divide (as nucleus) is in interphase/not in mitosis
Do not award a mark for stating that the goblet cell lacks a nucleus.
a. cell cycle is a sequence of stages / cell cycle is G1, S, G2 and mitosis
b. (control of the cell cycle) by cyclins/cyclin
c. levels of cyclins rise (and fall)/fluctuate during the cell cycle/surge at different times/have to reach a certain concentration
d. conditions inside as well as outside the cell affect regulation
e. four cyclins/different cyclins to enter different stages of/events in the cell cycle / cyclins regulate the sequence/timing of the cell cycle / cyclins trigger the next stages
The idea of different cyclins acting at different phases must be clear.
f. cyclin-dependent kinases / cyclins bind to kinases and activate them
g. kinases phosphorylate other proteins
h. phosphorylated proteins perform specific functions in the cell cycle