cell membrane and cell wall

12TH PHYSICS

Components of the cell
The major components of the cell are cell membrane cytoplasm and nucleus
Cell membrane plasma membrane
Is cell has a limited boundary the cell membrane and plasma membrane or plasmalemma it is a living membrane outermost in animal cells but internal to cell wall in plant cells in food vectors in the formation of pseudopodia in amoeba

The plasma membrane is made of proteins and lipids and several models were proposed regarding the arrangement of proteins and the fluid mosaic model proposed by singer and nicolson only is widely accepted it is represented in according to the fluid mosaic model of plasma membrane is composed of A Leopard by lip year of phospholipid molecules into which a variety of globular proteins are embedded
Is phospholipid molecule has two ends and outer head hydrophilic IEEE water attracting and the Enna tail pointing centrally hydrophobic IEEE water repairing the protein molecules are arranged in two different ways peripheral proteins for extinction proteins these proteins are present on the outer and inner surface of liquid by integral proteins or intrinsic proteins these proteins penetrate the Leopard bilayer partially aur wali
Functions the plasma membrane encloses the cell contents it provides cell safe in animal cell the characteristics of red blood cells Nerve cells and bone cells that allows transport of certain substances into and out of the cell but not all substance is so much it is termed selectively permeable of small molecules such as glucose amino acids what are mineral ions etc girls can be transported across the plasma membrane by any one of the following three methods diffusion molecules of substances move from their region of higher concentration to the reasons of lower concentration this does not require energy example absorption of glucose in a Cell Osmosis movement of water molecules from region of their higher concentration to the region of theory lower concentration through a semipermeable membrane there is no expenditure of energy in Osmosis this kind of movement is along concentration gradient
Active transport when the direction of movement of a certain molecule is opposite to that of diffusion IEEE from region of the lower concentration towards the region of their higher concentration it would required in active report by the cell for which energy is needed this energy is provided by ATP adenosine triphosphate the active transport may also be through a career molecule
Transport of large molecules bulk transport
During bulk transport the membrane changes its phone and shape it occurs in two ways endocytosis taking the substance in exocytosis passing the substance out
Endocytosis is of two types first phagocytosis intake of solid particles membrane force out going round the particle forming a cavity and the angle find the particle pinocytosis intake of fluid droplets membrane force in and forms a cup like structure and success in the droplets
Cell membrane regulate movement of substance into and out of the cell if the cell membrane fails to function normally the cell dies
Cell wall
In bacteria and plant cells The outermost cell cover present outside the plasma membrane is the cell wall about which we cell study now bacterial cell wall is made up of peptidoglycan given below is the structure and function of the plant cell structure most non living layer present in all plants secreted by the cell itself plants it is chiefly made up of cellulose but made also contain other chemical substances such as pectin and Lignin .
The substance constituting the cell wall is not simply h********** but it consists of fine Threads of fibres called microfibrils it may be thin 1 Micron and transparent as in the cells of onion peel in some cases it is very thick as in the cells of word
Functions of the cell wall protects the delicate inner parts of the cell being received it gives shape to the cell as it is rigid it does not allow distance of the cell does leading to Tatti of the cell that is useful in many ways it freely allows the passage of water and other chemicals into and out of the cell there are breaks in the primary wall of adjacent cells through which cytoplasm of one cell remains connected with the other. This cytoplasmic stands which connect one cell to the other one are known as plasmodesmata was of two adjacent cells are family joined by a cementing material called middle level are made of calcium pectinate

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