a specialized part of a cell having some specific function;a cell organ.
Animal cells are eukaryotic cells, or cells with a membrane-bound nucleus. Unlike prokaryotic cells, DNA in animal cells is housed within the nucleus.
Plant cells are eukaryotic cells that differ in several key aspects from the cells of other eukaryotic organisms. Their distinctive features include:
- A large central vacuole
- A cell wall composed of cellulose and hemicellulose
- Specialized cell-to-cell communication pathways known as plasmodesmata
- Plastids, the most notable being the chloroplast, which contains chlorophyll
- Cell division by construction of a phragmoplast
- The sperm of bryophytes and pteridophytes, Cycads and Ginkgo have flagella
The three tenets to the cell theory are as described below:
- All living organisms are composed of one or more cells
- The cell is the most basic unit of life
- All cells arise from pre-existing, living cells
cells --> tissues --> organs --> organ systems --> organisms