Biology HL
Cell Architecture and Microscopy
- 1.
Cell X has ribosomes, a plasma membrane and circular DNA not enclosed by a nuclear envelope. Cell Y has a nucleus and mitochondria. Identify the cell types and give two structures they share with a function for each, explaining why lack of a nucleus does not mean X lacks genetic information.
[4 marks] · no calculator - 2.
A micrograph shows a cell 36 mm long at a magnification of x1200. Calculate its actual length in micrometres. Explain the difference between increasing magnification and improving resolution, and why cell length alone cannot establish whether the cell is prokaryotic.
[4 marks] - 3.
Mitochondria contain DNA and ribosomes and divide within cells. Explain how these observations support endosymbiosis, give one further relevant structural feature, and explain why no single feature alone proves the historical explanation.
[4 marks] · no calculator - 4.
A cell measures 48 mm across in a printed micrograph. A 12 mm scale bar represents 3.0 micrometres. Calculate the cell's actual width and the magnification of the printed image. Explain why the scale bar remains useful after uniform resizing of the entire image.
[4 marks] - 5.
A hypothetical cell contains membrane-bound nuclei and mitochondria. Compare its DNA organisation with that of a typical bacterium, and explain how mitochondrial DNA provides evidence consistent with endosymbiosis without proving it from this observation alone.
[4 marks] · no calculator