AS Biology Bridging Task
Background Information
Looking at Cells
Cells are very small. Most are too small to be seen with the naked eye, and certainly not in any detail. In
order to investigate cells, images need to be produced that are both enlarged and more detailed. The first
light microscope was developed by Robert Hooke in the 1660s, and since then, light microscopes have
improved and electron microscopes have been developed. This has allowed scientists to study cells in
detail.
Organelles and Ultrastructure
When a cell is viewed under the microscope, the most obvious feature visible is the very large nucleus.
Other structures may be visible, such as chloroplasts and large vacuoles in plant cells. These structures are
called organelles. Using an electron microscope, it is possible to identify a range of organelles in plant and
animal cells. The detail of the inside of the cells, as revealed by the electron microscope, is termed the
cell’s ultrastructure (sometimes called fine structure).
Task
As preparation for the AS level Biology course, you are required to write a report on the ultrastructure of
plant and animal cells as seen by an electron microscope. You need to include:

Large, labelled diagrams showing the ultrastructure of an animal cell and a plant cell.

Details about the following organelles:
- plasma (cell surface) membrane
- nucleus
- mitochondrion
- chloroplast
- endoplasmic reticulum (rough and smooth),
- ribosomes
- golgi apparatus
- lysosomes
- microtubules
- plasmodesmata as plant cell to cell junctions

For each organelle you must include a labelled, hand-drawn sketch in pencil, a description of their
structure and an outline of their function.
Suggested resources
http://www.cellsalive.com/cells/cell_model.htm
www.wiley.com/legacy/college/boyer/0470003790/animations/cell_structure/cell_structure.htm