Cell structure — Cambridge IGCSE Combined Science

Revision notes

4 short notes, in the order of the specification. Each one in short:

1. Plant and animal cells

   Plant and animal cells both have a cell membrane, cytoplasm, a nucleus, ribosomes and mitochondria. Plant cells also have a cellulose cell wall that strengthens the cell, chloroplasts that absorb light energy for photosynthesis, and a large vacuole containing cell sap. The cell wall is fully permeable, while the cell membrane controls what enters and leaves.

2. Bacterial cells

   A bacterial cell is a simple cell with a cell wall, cell membrane, cytoplasm and ribosomes but no nucleus. Its genetic material is a single loop of circular DNA lying free in the cytoplasm, and it may also have plasmids, which are small rings of extra DNA. Its cell wall is not made of cellulose.

3. Specialised cells

   Supplement

   A specialised cell has a shape and contents suited to one function, such as root hair cells for absorption and red blood cells for oxygen transport.

4. Cells, tissues, organs and organ systems

   Organisms are organised in levels: cell, tissue, organ, organ system and organism. A tissue is a group of cells with similar structures working together to perform a shared function. An organ is a group of tissues working together, and an organ system is a group of organs with related functions, such as the digestive system.