Nucleolus: Fontana (1781) discovered the presence of round oval bodies called Nucleoli (Nucleolus-singular) embedded in the nucleoplasm. It does not have a membrane. Nucleoli are associated with the nuclear organizing portion of the chromosomes. The size of the nucleoli is related to the activities of the cell. Cells that are actively involved in protein synthesis … Read more

Nucleus is the heart of the cell. It controls all the cellular activities. So it is referred to as the controlling centre of the cell. It was first discovered by Robert Brown in 1831. The study of nucleus is termed as Karyology. Nucleus is present in all eukaryotic cells except mature RBC of humans and … Read more

Centrioles are non – membranous cylindrical bodies found near the nucleus in the centrosome, a granular mass that serves as an organizing center for microtubules. These are seen in animal cells and flagellated plant cells. Centriole can be viewed only during cell division. Centrosome usually contains two centrioles. A pair of centrioles is called diplosome. They … Read more

Ribosomes are ribo-nucleo-protein particles found in almost all cells. These are the assembly shops for protein synthesis. So they are described as protein factories. They are found in the cytoplasm or attached to the endoplasmic reticulum. Ribosomes were first observed by Claude and named them as microsomes. George Palade (1953) named them as ribosomes. Ribosomes … Read more

These are present only in plant cells. They synthesize and store carbohydrates. The term plastid (Plastikas -formed) was proposed by Schimper in 1885. The plastids are broadly classified into two main types – Chromoplasts and Leucoplasts. Chromoplasts These are coloured plastids, which contain various pigments. Based on their colour, chromoplasts are further subdivided into Chloroplast, … Read more

Mitochondria are thread like or granular cytoplasmic organelles (mito-thread, chondrion-granule). It was first observed by Flemming and Kolliker in 1882. The term mitochondria were introduced by Benda in 1898. They are found both in plant and animal cells, but absent in prokaryotes. The number of mitochondria is particularly related to the functional state of the … Read more

Lysosomes are tiny bags filled with digestive enzymes concerned with intracellular digestion. These are the recently discovered organelles of the cell. It occurs in most animal cells and in a few plant cells. It is a lytic body. It destroys the cell in which it is produced. So it is called suicidal bag. As the … Read more

It is a cluster of smooth membranes associated with ER. It was first described by Camillo Golgi. It has been previously named as Golgi body, dictyosome, lipochondrion etc. The term dictyosome is usually used to denote the Golgi body of invertebrates and plants. The size and shape of the Golgi complex varies from cell to cell. … Read more

The Endomembrane system includes Endoplasmic reticulum Golgi complex Lysosomes and Vacuoles. The functions of these organelles are well coordinated.   Endoplasmic reticulum The Endoplasmic reticulum is a network of membrane bound cavities, vesicles and tubules distributed throughout the cytoplasm. It is the cytoskelteon of the cell. The name Endoplasmic reticulum was coined by Porter. ER … Read more

The surface of some eukaryotic cells are decorated, clothed or masked by certain carbohydrates bound to proteins (glycoprotein) and lipids (glycolipids). This carbohydrate rich filamentous layer is called cell coat or glycocalyx. Functions of cell coat It protects the cells from mechanical and chemical damage. It provides a micro environment for the cells. It helps … Read more