What is Cell Cytoplasm?
The protoplasmic contents of a cell excepting the nucleus are called cytoplasm. The semiliquid and granular part of the cell (or protoplasm) that remains extended from plasma membrane to nuclear membrane is known as cytoplasm.
Cell Cytoplasm is a colloidal material. It is composed of three distinct types of components-(i) Cytoplasmic matrix, (ii) Cytoplasmic organelles and (iii) Cytoplasmic inclusions or Ergastic substances.
What is Cytoplasmic Matrix?
The fluid ground substance of cytoplasm, in which the organelles and inclusions remain suspended is called Cytoplasmic matrix. This transluscent fluid part of cell cytoplasm is also called hyaloplasm. It is composed of water and various inorganic and organic materials e.g., salts, sugars, amino acids, proteins, enzymes, etc., that remain either in dissolved (solutes) or in dispersed (colloidal particles) state. This part of cytoplasm is also known as cytosol or soluble fraction of cytoplasm because it is detached as the remaining supernatant after precipitation of all the organelles by centrifugation during cell fractionation. It is composed of water and various inorganic and organic materials e.g., salts, sugars, amino acids, proteins, enzymes, etc., that remain either in dissolved (solutes) or in dispersed (colloidal particles) state. It contains soluble RNA or transfer RNA (sRNA or tRNA).
The peripheral thin part of cytoplasmic matrix which is relatively transparent, non-granular, more viscous and inflexible is called ectoplasm (or plasmagel or cortex of cytoplasm), whereas the inner granular and less viscous part of it is called endoplasm (or medulla of cytoplasm). The thin layer of cytoplasm that surrounds the vacuoles is known as tonoplasm.
Functions of cytoplasmic matrix
i) It carries the cytoplasmic organelles and inclusions.
ii) It imparts the colloidal properties of protoplasm e.g., sol-gel transformation, viscosity changes, intracellular movements such as cyclosis.
iii) It gives origin to the fibrillar components and microtubules in certain cells, myofibrils in muscle cells, keratinised tonofilaments in epithelial cells, etc.
iv) It contains the enzymes responsible for some metabolic processes e.g., glycolysis, fatty acid synthesis, etc.
v) It maintains the internal milieu of the protoplasm.
What are the Cytoplasmic Organelles?
The living structures of cell cytoplasm that remain dispersed in the matrix are called cytoplasmic organelles. Most of these are unit membrane bound structures. Unlike the prokaryotic-cells, several such membrane bound organelles are found in eukaryotic cells : these are mitochondria, endoplasmic reticulum, ribosome, Golgi body, microtubules, centrosome, lysosome, plastid and vacuole. Each organelle is responsible for some important functions of the cell.