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- All life on Earth exists as cells. These have basic features in common. Differences between cells are due to the addition of extra features. This provides indirect evidence for evolution.
- All cells arise from other cells, by binary fission in prokaryotic cells and by mitosis and meiosis in eukaryotic cells.
- All cells have a cell-surface membrane and, in addition, eukaryotic cells have internal membranes.
- The basic structure of these plasma membranes is the same and enables control of the passage of substances across exchange surfaces by passive or active transport.
- Cell-surface membranes contain embedded proteins. Some of these are involved in cell signalling – communication between cells. Others act as antigens, allowing recognition of ‘self’ and ‘foreign’ cells by the immune system. Interactions between different types of cell are involved in disease, recovery from disease and prevention of symptoms occurring at a later date if exposed to the same antigen, or antigen-bearing pathogen.
Source: AQA Spec
Included in this download
|3.2.2||All cells arise from other cells|
|3.2.3||Transport across cell membranes|
|3.2.4||Cell recognition and the immune system|