Cell the fundamental unit of life

Cell is a structural and functional unit of all living organisms. Cells are the building blocks of an organism like the brick which is a building block for a house.

The organisms can be classified into two groups based on the number of cells they have.

they are UNICELLULAR and MULTI CELLULAR organisms.

Unicellular organisms are those which have a single cell and all the activities of a living body like digestion excretion and respiration takes place in a single cell. example for unicellular is Amoeba it takes food by endocytosis, digest and excrete it by exocytosis. ENDOCYTOSIS:is a form of active transport in which a cell transports molecules (such as proteins) into the cell (endo- + cytosis) by engulfing them in an energy-using process. EXOCYTOSIS: materials are exported out of the cell via secretory vesicles.

Multi cellular organisms are those organisms which has different specialized cells for different functions of a living body. example is human, humans have different organ system for different functions which are made up of certain tissue which in turn consist of a similar type of cells. the cell has some basic components like cell membrane, nucleus, cytoplasm.

1)CELL MEMBRANE:The cell membrane (plasma membrane) is a thin semi-permeable membrane that surrounds the cytoplasm of a cell. Its function is to protect the integrity of the interior of the cell by allowing certain substances into the cell, while keeping other substances out. It also serves as a base of attachment for the cytoskeleton in some organisms and the cell wall in others. Thus the cell membrane also serves to help support the cell and help maintain its shape.

2)NUCLEUS: has the genetic information which is stored in chromosomes and that has to be passed to the next generation. It also contains nucleoplasm and nucleolus. Nucleus is bounded by nuclear membrane. It is a sphere-shaped organelle found in eukaryotic cells. FUNCTIONS OF NUCLEUS 1)It controls the heredity characteristics of an organism. 2)It is responsible for protein synthesis, cell division, growth and differentiation. 3)Stores heredity material in the form of deoxy-ribonucleic acid (DNA) strands. Also stores proteins and ribonucleic acid (RNA) in the nucleolus. 4)It is a site for transcription process in which messenger RNA (m RNA) are produced for protein synthesis. 5)Aids in exchange of DNA and RNA (heredity materials) between the nucleus and the rest of the cell. 6)NUcleolus produces ribosomes and are known as protein factories. 7)It also regulates the integrity of genes and gene expression.

3)CYTOPLASM: is a jelly like substance which helps to hold all the cell organelles in it. cytoplasm along with nucleoplasm makes protoplasm which is a living thing. cell organelle are membrane bound structures found in the cytoplasm every cell organelle perform certain function. the cell organelle are endoplasmic reticulum, golgi apparatus, lysosome, mitochondria, plastids, vacuoles,

endoplasmic reticulum is a membrane bound structure. It is of two types rough endoplasmic reticulum and smooth enoplasmic reticulum. rough endoplasmic reticulum has ribosomes which produce protein. Endoplasmic recticulum is present in three forms cristerne,vesicle and tubular form. In endoplasmic recticulum the hydrolinase enzyme is formed by the break down of proteins and other substance in recticulum. There are two types of endoplasmic recticulum :

1) Rough endoplasmic recticulum(RER)

RER has RIBOSOMES on its surface. The main function of ribosome is protein synthesis.

2) Smooth endoplasmic recticulum(SER)

SER do not have ribosomes on its surface. Its main function is synthesis of lipid.

golgi apparatus takes up the proteins from endoplasmic reticulum and packs, modify and also store it. Golgi bodies are present near to endoplasmic recticulum. Lysosomes are produced by golgi bodies.

Plastids are present only in plant cell and some bacteria it helps in photosynthesis. There are three types of plastids chromoplast,leucoplast and chloroplast. Leucoplast are the colourless plastids, chloroplast are green coloured plastids and chromoplast are coloured plastids other than chloroplast.

Vacuoles are big in plants and small or absent in animals. It stores food and water.