Question 18N.2.SL.TZ0.5
| Date | November 2018 | Marks available | [Maximum mark: 15] | Reference code | 18N.2.SL.TZ0.5 |
| Level | SL | Paper | 2 | Time zone | TZ0 |
| Command term | Discuss, Draw, Outline | Question number | 5 | Adapted from | N/A |
The structure of prokaryotic cells has been investigated using electron microscopy. Draw a labelled diagram to show prokaryotic cell structure.
[4]
a. cell wall — a uniformly thick wall ✔
b. pili — hair-like structures connected to cell wall
OR
flagellum — at one end only, longer than pili ✔
c. plasma/cell membrane — represented by a continuous single line ✔
May be labelled as the innermost wall line
d. «70S» ribosomes — drawn as small discrete dots not circles ✔
e. naked DNA/nucleoid — region with DNA not enclosed in membrane ✔
f. cytoplasm — the non-structural material within the cell ✔
Award [1] for each structure clearly drawn and correctly labelled
Award [2 max] if any eukaryotic structure is drawn and labelled
Outline the reasons for differences between the proteomes of cells within a multicellular organism.
[4]
a. all the genome is the same in all the cells of an organism ✔
b. the genome/DNA/genes instructs the production/expression of proteins/proteome ✔
c. the proteome is all the proteins produced by a cell ✔
d. the proteome varies with the function/location/cell differentiation/environmental conditions of the cell ✔
e. specific genes are expressed/turned on/off in different cells ✔
f. «turning on/off» according to a required function ✔
Accept a specific example (eg: insulin only produced in pancreas)
Discuss the cell theory and its limitations.
[7]
cell theory:
a. cell theory is the accepted explanation of life ✔
b. organisms are composed of «one or more» cells ✔
c. cells are the basic/fundamental/smallest units of life ✔
d. cells can only come from pre-existing cells ✔
e. spontaneous generation of life has been disproven ✔
limitations:
f. striated muscle cells contain many nuclei «while most eukaryotic cells have one nucleus»
OR
red blood cells have no nucleus «while most eukaryotic cells have one nucleus» ✔
g. giant algae have complex single cell structure
OR
organisms as large as giant algae would be expected to be multicellular, but they have only one cell with one nucleus ✔
h. aseptate fungal hyphae are tube-like structures that contain no cell membranes between the many nuclei
OR
slime molds contain many nuclei ✔
i. viruses have some characteristics of living organisms but are not cells ✔
j. if all cells come from pre-existing cells, where did the first one come from? ✔
Allow description of Pasteur’s experiments
Do not accept a list of limitations without explanation
