Definition: Vacuoles (L. vaccus = empty) are lifeless membranous fluid filled sacs present within the cytoplasm. Types: According to their contents vacuoles maybe classified into following types: (i) Sap vacuole: It is the most common types of vacuole, occurring in higher plants cells. (ii) Protein bodies: These are specialized protein storing vacuoles present abundantly in seeds. During germination, the stored [...]
History: Van Benden (1887) first discovered centrosome. T. Boveri (1888) coined the term centrosome. Occurrence: Centrosome mostly present in all animal cells, motile cells of many green algae, bryophytes, pteridophytes and cycads. Centrosome is absent in prokaryotic cells, amoebae, some algae, higher fungi, higher gymnosperms and in all angiosperms. Structure: Centrosome or cell centre is a non- membranous organelle usually [...]
Cilia (L. cilium =eye lash) and flagella (Gr. flagellum - whip) are fine hair-like protoplasmic outgrowths of cells and take part in cell motility. These organelles were first reported by Englemann (1868). Cilia and flagella are basically similar but they vary in number, length and patterns of movement. Cilia are smaller (5-10, wm) and numerous but flagella are longer (100-200fim) [...]