AQA Biology A-Level - Cell Structure and Microscopy QP
Q1.
Uronema marinum is a single-celled eukaryotic organism. The diagram below is
a photograph of U. marinum taken through an optical microscope.
(a) Explain why it is not possible to determine the identity of the structures
labelled X using an optical microscope.
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
(2)
(b) U. marinum cells ingest bacteria and digest them in the cytoplasm.
Describe the role of one named organelle in digesting these bacteria.
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
(3)
Page 1 of 25
,AQA Biology A-Level - Cell Structure and Microscopy QP
(c) Calculate the actual length of the cell shown between Y and Z in the
diagram above.
The magnification of the image is × 900
Give your answer in μm and to 2 significant figures.
Show your working.
Answer __________ μm
(2)
Q2.
(a) Give two structures found in all prokaryotic cells and in all eukaryotic cells.
1 _________________________________________________________
2 _________________________________________________________
(2)
All prokaryotic cells contain a circular DNA molecule and some prokaryotic cells
contain plasmids.
(b) Scientists have found that the rate of plasmid replication is faster in cells
growing in a culture with a high concentration of amino acids than in a
culture with a lower concentration of amino acids.
Suggest one explanation for the faster rate of plasmid replication in cells
growing in a culture with a high amino acid concentration.
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
(2)
Page 2 of 25
, AQA Biology A-Level - Cell Structure and Microscopy QP
A scientist prepared a culture of a bacterial species.
• She extracted the plasmids and the circular DNA molecules from a sample
of cells taken from this culture (A).
• She then added antibiotic X to the culture and let the cells divide for 4
hours.
• She then extracted the plasmids and the circular DNA molecules from a
sample of these cells (B).
• The scientist separated the plasmids from the circular DNA molecules in A
and in B using ultracentrifugation.
The figure below shows her results.
(c) What can you conclude from the figure above about a structural difference
between the plasmids and the circular DNA? Explain your answer.
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
(2)
Page 3 of 25
Q1.
Uronema marinum is a single-celled eukaryotic organism. The diagram below is
a photograph of U. marinum taken through an optical microscope.
(a) Explain why it is not possible to determine the identity of the structures
labelled X using an optical microscope.
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
(2)
(b) U. marinum cells ingest bacteria and digest them in the cytoplasm.
Describe the role of one named organelle in digesting these bacteria.
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
(3)
Page 1 of 25
,AQA Biology A-Level - Cell Structure and Microscopy QP
(c) Calculate the actual length of the cell shown between Y and Z in the
diagram above.
The magnification of the image is × 900
Give your answer in μm and to 2 significant figures.
Show your working.
Answer __________ μm
(2)
Q2.
(a) Give two structures found in all prokaryotic cells and in all eukaryotic cells.
1 _________________________________________________________
2 _________________________________________________________
(2)
All prokaryotic cells contain a circular DNA molecule and some prokaryotic cells
contain plasmids.
(b) Scientists have found that the rate of plasmid replication is faster in cells
growing in a culture with a high concentration of amino acids than in a
culture with a lower concentration of amino acids.
Suggest one explanation for the faster rate of plasmid replication in cells
growing in a culture with a high amino acid concentration.
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
(2)
Page 2 of 25
, AQA Biology A-Level - Cell Structure and Microscopy QP
A scientist prepared a culture of a bacterial species.
• She extracted the plasmids and the circular DNA molecules from a sample
of cells taken from this culture (A).
• She then added antibiotic X to the culture and let the cells divide for 4
hours.
• She then extracted the plasmids and the circular DNA molecules from a
sample of these cells (B).
• The scientist separated the plasmids from the circular DNA molecules in A
and in B using ultracentrifugation.
The figure below shows her results.
(c) What can you conclude from the figure above about a structural difference
between the plasmids and the circular DNA? Explain your answer.
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
(2)
Page 3 of 25
