Structures and Functions of Important Cell Organelles, Importance of Water
Definition of Cell:
A cell may be defined as "Structural and functional unit of all living organisms".
Two types of cells
1) Eukaryotic cell
2) Prokaryotic cells
Important Plant Cell – Organelles and their Functions:
1) Cell Wall – It Provides support, prevent cells from swelling and rupture or shrinkage, gives definite shape to cell.
2) Nucleus – Store of genetic information, which issue appropriate signal at proper time during different stages.
3) Mitochondria- Power house of energy, contain m-t RNA and DNA and protein synthesizing machinery, synthesis of ATP required for anabolism.
4) Chloroplast – The sites of photosynthetic phosphorylation. The stroma is the site of the carbon photosynthetic enzymes involved in CO 2 fixation, ribosomes, nucleic acid-synthesizing enzymes, and fatty acid synthesizing enzymes.
5) Ribosomes – Site of protein biosynthesis.
6) Golgi Apparatus – Participate in the early stage of cell wall synthesis in higher plants. Sites of secretions of proteins and polysaccharides and coupling of these two components to form glycoproteins. Intense phospholipid biosynthesis observed in these organelles.
Importance of Water:
i) Serves as a medium in which substances undergo fundamental changes.
ii) Provides hydrogen for the reduction of CO2 in photosynthesis.
iii) Water is necessary reactant for the hydrolytic splitting of carbohydrates, fats and proteins.
iv) Water is solvent and dispersion medium for all protoplasmic constituents
v) Acts as a transporting medium for all the cell nutrients.
vi) Absorption, secretion and excretion would not be possible without water.