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
Endocytosis: It is the engulfing of food or foreign particles through the plasma membrane. It is of two types – phagocytosis (cell eating), and pinocytosis (cell drinking). Phagocytosis refers to the engulfing of solid particles Pinocytosis is the engulfing of liquid particles. A pinosome or phagosome is a membrane bound vesicle that encloses the liquid … Read more
The plasma membrane (cell membrane, plasma lemma) is a thin, elastic, semi permeable living membrane found on the outer surface of all protoplasts. It separates the cellular protoplasm with their environment. The term plasma membrane was coined by Nageli and C.Cramer in 1855. Unit membrane concept: Danielli and Davson had proposed a Sandwich Model for … Read more
A typical eukaryotic cell is bounded by a plasma membrane. Cell wall is present in the case of plant cells, The protoplasm is divisible into nucleus and cytoplasm. The cytoplasm is in constant motion called cytoplasmic streaming. The streaming movement of cytoplasm around the vacuole is called cyclosis. It contains membrane bounded bodies called organelles, … Read more