CELL, Structure Cell ,cell Wall, Nucleus,Cell Membrane, Cytoskeleton,Type

 Cells are the microscopic structures that form the foundation of life. Cell are the units that carry out all the functions necessary for life.

2.1-Cell

The cell is the basic unit of life. Just as bricks are the building blocks of a house cell are the building block of living organism including plants , humans and animals. Everything, from the smallest bacterium to the largest whale ,is made of cells. Most of the cell are very small and cannot be seen with the naked eye. Some cells are large enough to be seen with naked eye for example egg cell of ostrich .

2.2 structure of cell

Basic structure of a cell was discovered by an English scientist Robert Hooke. In 1665 using a simple microscope ,Hooke examined as thin slices of crock and discovered tiny box like structure that he" called cell". He could not study the details of the internal structure of cell. However in the 19th century the quality of microscope improved. In 1831 while studying plant cells under a microscope, scientist Robert Brown observed the "nucleus". There are two basic type of cell prokaryotic and eukaryotic. Prokaryotic cell are simple and do not have membrane bounded organelles . Eukaryotic cells are more complex and have membrane bounted organelles.

Cell Wall

The cell of bacteria ,fungi ,plant and some protista have a rigid non living wall around cell membrane. It is called cell wall. It provided shapes, strength protection and sport to the inner leaving matter of the cell. The plant cell wall is made of three layer i.e middle lamella primary wall and secondary wall. 

(1) Primary Wall 

The primary wall is present just above the cell membrane. It is mainly composed of cellulose hemicellulose and pectin. Cellulose form fibres that crisscross over one another to form strong primary wall.

(2) Middle lamella 

Middle lamella hold together the primary wall to adjacent cells which contain magnesium, calcium, pectin.

(3) Secondary wall

Xylem cell make secondary wall on the inner side of primary wall. It is mainly made of cellulose Lignin and other chemicals.

 Cell Membrane 

All cell have thin and elastic cell membrane around the cytoplasm.It is selectively permeable.It hello very few molecule to pass through it while block many other molecules. Cell membrane is composed of protein and leopard and small quantities of carbohydrates. The structure of cell memory is described as fluid mosaic model. According to this models the lipids made upload like by layer in which protein molecule are submerged. The leopards and proteins can move laterally. Due to these movement the pattern are "mosaic"of lipid and protein constantly changes. Carbohydrates are joined with proteins are with lipids. In eukaryotic cell many organelles mitochondria chloroplast Golgi apparatus and endo plasmic reticulum and lysosomes are bounded by membrane.

Cytoplasm 

it is Jelly like  substance that fill the inside of cell. It is a complex mixture of water protein enzymes salt and other substances. Cytoplasm provide a medium for organelles to move and function. It also helps in the transport of material throughout the cell. It act as the site for various metabolic reaction example glycolysis .It also stores food and wastes of the cell.

Nucleus 

Are Eukaryotic cells have a prominent nucleus. In animal cells, it is present in the centre. It is push to sight due to a large central vacuole. The nucleus is bounded by the double membrane known as nuclear envelope. It is semi permeable and has many small pores called nuclear pores. The inner Jelly like material of nucleus is called "nucleoplasm". In nucleoplasm there are 1 hour more small bodies called "nuclei". Here ribosomes are assemble. Nucleoplasm contain fine thread like structure known as "chromatin". It is composed of deoxyribonucleic acid and protein. When a cell starts dividing it chromatin condense and take the shape of thick chromosome. DNA contain Jean which control all the activities of the cell. DNA is also responsible for the transmission of characteristics to the next generation. That is why it is called the heredity material.

Cytoskeleton 

It is network of thin tubes and present throughout the cytoplasm.it consist of three part i.e micro tubules  microfilaments intermediate.

(1)Microtubules 

Are hollow tube made up tubulin protein. This part holds organelles in place maintain a cells shape and act as tracks for organelles. Micro tubules also make mitotic,cilia and flagella.

(2) Microfilaments

Are finer than Microtubules. There are made up of contractile protein mainly actin. they help in cell movement the wralling of white blood cells and the construction of muscle cell.

(3) Intermediate filaments 

A rod made of variety of protein mainly keratin and vitamin. The anchor the nucleus and some other organelles in the cell they also make cell to cell junctions.