Introduction to Eukaryotic Cells and Organelles (A-level Biology)
Introduction to Eukaryotic Cells and Organelles
Cell Theory
- All organisms are made up of cells. Cell Theory is the idea that all living organisms are made up of cells, and all cells are essentially made up of the same fundamental structures. This means that all life is fundamentally the same in terms of structure and requirements for function.
- In complex organisms, cell theory also goes on to state that cells are the fundamental building block of an organism. Cells make up tissues, and these tissues make up organs, and the organs make up organ systems which finally make up the organism.
Cells → tissues → organs → organ systems
Eukaryotes and Prokaryotes
All life on Earth can be divided into two very broad classes:
- Prokaryotes are single cells organisms, like bacteria, which lack a true nucleus.
- Eukaryotes are single celled and multicellular organisms which have a true, membrane bound nucleus.
What is a Eukaryotic Cell?
- Eukaryotic cells have a true membrane bound nucleus and membrane bound organelles. Membrane bound simply means that the nucleus and organelles are surrounded by a membrane, typically a phospholipid bilayer style membrane.
- Animal, plant, algal and fungal cells are eukaryotic. We will look at the three groups further in future tutorials.
Overview of Organelles
- Organelles are substructures within cells. Every organelle within a cell has a special function that contributes to the overall functioning of that cell.
- Every organelle has its own distinct structure and function. In later tutorials we will cover the different organelles in more detail. Some organelles can be found across all eukaryotic cells, while some are unique to specific types of eukaryotes e.g. chloroplasts in plants.
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