From today we are going to start to make the notes of every chapter of according to mdcat syllabus. I have collected all this data from different province book and also federal books. I have also read different entry test books like kips preparation books. As We take different lectures and read different books and make notes and after we revise all them and it is difficult for us. So I have decided to publish all these data on this single platform , so we can read all of these books only by reading these blogs . It will safe time for us.
Cell wall: Cell wall is the outermost boundary of most of Plants cells. The epidermals cells have cutin with primary walls which form cuticle and it provides high tensile strength. It is not present in animals cells while fungi, algae and prokaryotes also have cell wall as well. The thickness of cell wall varies in different plant cells.- The cell wall is secreted by cell protoplasm. It is porous and allows free passage of water and others materials. So It is not involved in transport of materials inside and outside of cells.
- Cell wall of plants is made up of cellulose while of prokaryotes is made up of peptidoglycan or murein. Cell wall of fungi is made up of chitin.
- The cellulose fibers are arranged in criss cross arrangement and the layers of these fibers are right angle to each other.
- Cell wall provides definite shape and rigidity to cell and does not act as barrier for materials. It prevents cell from osmotic lysis.
- The Primary wall is true wall and develop in newly growing cells. It is thin and slightly flexible. It is made of cellulose and some amount of hemicellulose and pectin. It is adapted for growth. This stretches plastically.(irreversibly). It is also involved in cell to cell interaction.
- Middle lamella is formed in between the primary cell walls of the neighbouring cells. It is sticky and composed of salts of calcium and magnesium in the form of gel.
- The secondary wall is growing inner to the primary wall. It is dead and is thick and rigid. This wall grow when cell completes its growth. It is present in between the primary wall and plasma membrane in sclerenchyma cells. It is composed of cellulose, hemicellulose, lignin, inorganic salts, slica and waxes. Lignin molecules in this wall are responsible for rigidness as it anchors with cellulose.
Cell membrane: It is the outermost boundary in animal cells and in plant cells, it is covered by cell wall. It is found in all living cells. It is called sarcolema in muscle cells and neurlemma in nerve cells. It is composed of 60-80% of proteins and 20-40% of lipids. Carbohydrates are also present in little amount. There are two models to explain the structure of membrane:
1:-Unit membrane: The cell membrane is composed of lipid bilayer sandwhiced between inner and outer layer of proteins.
2:-Fluid Mosaic manner model: According to this model, proteins are embedded in lipid layers in mosaic manner. This model is acceptable at this time.
Cell membrane also contain charged pores through which movement of materials take place by active transport or by passive transport. Cell membrane is asymetrical: its two layers are not identical. The plasma membrane is made up of phosphoglyceride.
The cell membrane thickness is about 7nm.In membrane , the lipid bilayers are arranged in such way that their hydrophobic ends face each other while hydrophilic ends are on the surface of membrane.
The steroids and cholesterol are also present. Carbohydrates gernally attach with proteins or to lipids to form conjugate molecules on the upper surface of membrane. The proteins in the membrane determine most of its functions. The substance which are lipids soluble cross it more easily while the ions being charged particles have some difficulty in its crossing. Many substance constantly enter and leave the cells. Small molecule being neutral also cross the cell membraneIn animal cells, cell membrane takes materials inside by unfolding called endocytosis which may be: taking in solid materials (phagocytosis) or taking in liquid materials (pinocytosis). In nerve cells cell membrane help in transport of nerve impulses.Proteins present in cell membrane may act as carrier of substance or the channels through which substance can move inside the cell. Some proteins of this membrane have enzymatic function.
Some proteins are act as receptors and receive signals from other cells and in thus way these brings intra cellular response .Some are antigen which help to recognize others.eg. the forgein integen is recognized and attacked by immune systems. The conjugate molecules are cell surface markers and stick cells to form tissue.
1:-Unit membrane: The cell membrane is composed of lipid bilayer sandwhiced between inner and outer layer of proteins.
Cell membrane also contain charged pores through which movement of materials take place by active transport or by passive transport. Cell membrane is asymetrical: its two layers are not identical. The plasma membrane is made up of phosphoglyceride.
The cell membrane thickness is about 7nm.In membrane , the lipid bilayers are arranged in such way that their hydrophobic ends face each other while hydrophilic ends are on the surface of membrane.
The steroids and cholesterol are also present. Carbohydrates gernally attach with proteins or to lipids to form conjugate molecules on the upper surface of membrane. The proteins in the membrane determine most of its functions. The substance which are lipids soluble cross it more easily while the ions being charged particles have some difficulty in its crossing. Many substance constantly enter and leave the cells. Small molecule being neutral also cross the cell membraneIn animal cells, cell membrane takes materials inside by unfolding called endocytosis which may be: taking in solid materials (phagocytosis) or taking in liquid materials (pinocytosis). In nerve cells cell membrane help in transport of nerve impulses.Proteins present in cell membrane may act as carrier of substance or the channels through which substance can move inside the cell. Some proteins of this membrane have enzymatic function.
Some proteins are act as receptors and receive signals from other cells and in thus way these brings intra cellular response .Some are antigen which help to recognize others.eg. the forgein integen is recognized and attacked by immune systems. The conjugate molecules are cell surface markers and stick cells to form tissue.
Cytoplasm:
- a region between nucleus and plasma membrane. It consist of 90% water and form solution and organelles, salts, sugar, fatty acid, and gasses.
- It act as store house for vital chemicals. The soluble part of cytoplasm is cytosol while pheripheral part is viscous and called cytogel.
- Some chemical process like glycolysis, translation occurs in cytoplasm. The freely floating cell organllese movement is due to Cytoplasm and called Cyclosis.
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