Cell & cell organelles and their functions
CELL
&
cell organelles and their functions
In 1838, the cell theory was proposed, according to this theory, the cell is both the structural and the functional unit of all living organisms.
What is a cell?
All the living organisms are made up of cells. A living cell may be defined as a compartment enclosed by a membrane that consists of several chemical constituents and it capable of propagating itself by division. Activity of an organism is dependent on the activity of its cells, individually and collectively.
There are two stages in evolution of the cell-
I) chemical evolution
ii) biological evolution
Chemical evolution:- chemical evolution started with the formation of organic molecules on the earth which had no life until then, it is also called prebiotic Earth.
Biological evolution :- molecular aggregates organised and from the cell which was different from the cell as it exist today.
Cell organelles and their functions
1.Cell organelles that present in animal cell.
- - Nucleus
- - Golgi apparatus
- - mitochondria
- - endoplasmic reticulum
- - lysosomes
- - Ribosomes
- - Centrioles
2. Cell organelles in plant cell
- - Golgi apparatus ( dictysome)
- - Endoplasmic reticulum
- - Nucleus
- - Mitochondria
- - chloroplast
- - Ribosome
- - Lysosomes
- - Vacuoles
Cell organelles and their functions
Endoplasmic reticulum
It is a complex system of a membrane sac, chambers and tubular canals. Endoplasmic reticulum is double membranous cell organelle. There are two types of endoplasmic reticulum : RER(rough endoplasmic reticulum) and SER ( smooth endoplasmic reticulum).RER is well developed in cells which are actively engaged in protein synthesis where as as SER is well developed in those cells which are actively involved in lipid synthesis.
Golgi apparatus
Golgi apparatus is a stack flattened sacs sorts out and processes proteins. It is located between endoplasmic reticulum and plasma membrane. Each dictysome has two faces having a proximal face near the nuclear membrane and that distal face which yields secretory vesicles.Nucleus
Nucleus is a double membranous structure. outer membrane or envelop remains in continuation with endoplasmic reticulum where as inner membrane encloses nucleoplasm. In nucleoplasm, the chromatin network is embedded. The nucleus contains DNA, RNA and proteins which are both acidic and basic.Mitochondria
Mitochondria, the powerhouse of the cell are cylindrical structures having outer and inner membranes. Inner membrane is folded into a number of cristae which expose F1 particles upon hydrolysis of membrane. Mitochondria Matrix contains DNA, ribosomes and all the enzymes which take part in tri carboxylic acid cycle (TCA).Lysosomes
Lysosomes have a digestive function both in plant and animal cells. They contain hydrolases which bring about digestion of the bio biological substances. lysosomes exhibit polymorphism which means occurrence of lysosome in different forms: primary lysosomes, secondary lysosomes, autophagic vacuoles and residual bodies.Chloroplast
Chromoplast are most abundant and are present in all green plants. Chloroplast contain a matrix substance that stroma in which number of lamellae or the thylakoid are suspended. The stacked thylakoid constitue grana.Chlorophyll, carotenoids and plastiquinone present in thylakoid membranes involved in photosynthesis. Chlorophyll is a green colour pigment present in chloroplast. The function of chlorophyll is to trap the light energy required for the formation of two product-ATP and NADPH.