Organisation: Cell Structure
Cell Structure
Basic Structures in All Cells
- Both animal and plant cells have a cell membrane which controls what comes in and out of the cell.
- They also both contain cytoplasm, a jelly-like substance where most of the cell's metabolic reactions occur.
- Nuclear material is present in all cells and carries genetic information. In some cells, this is found in a nucleus.
Additional Structures in Plant Cells
- Plant cells have a cell wall made of cellulose which supports the cell and maintains its shape.
- They also contain a permanent vacuole filled with cell sap to maintain internal pressure.
- Chloroplasts are present in green plant cells for photosynthesis, containing chlorophyll which absorbs sunlight.
Bacterial Cell Structure
- Bacterial cells are smaller and simpler, lacking a nucleus but still containing DNA, present in the cytoplasm.
- They possess a cell wall, membrane and cytoplasm, and may have additional structures like a flagellum (for movement) or plasmids (small rings of DNA).
Specialised Cells
- Cells in multicellular organisms often have specialised structures to carry out particular functions, such as red blood cells which are biconcave and lack a nucleus to maximise oxygen carrying capacity.
- In the leaf, the palisade cells contain many chloroplasts for efficient photosynthesis.
Microscopy
- Light microscopes allow us to observe cells and large organelles like nuclei and chloroplasts, but not smaller structures.
- Electron microscopes have a far higher resolution, letting us observe small organelles like ribosomes.