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Date November 2018 Marks available 4 Reference code 18N.2.SL.TZ0.5
Level Standard level Paper Paper 2 Time zone TZ0 / no time zone
Command term Draw Question number 5 Adapted from N/A

Question

The structure of prokaryotic cells has been investigated using electron microscopy. Draw a labelled diagram to show prokaryotic cell structure.

[4]
a.

Outline the reasons for differences between the proteomes of cells within a multicellular organism.

[4]
b.

Discuss the cell theory and its limitations.

[7]
c.

Markscheme

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

a.

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)

b.

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

c.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.

Syllabus sections

Core » Topic 1: Cell biology » 1.2 Ultrastructure of cells
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