1. PLASMA MEMBRANE (CELL MEMBRANE) : (i) Plasma membrane is a thin , semi-premeable membrane that surrounds the cell and regulates the movement of materials in and out of cell .(ii) movement of particles from a region of higher concentration to a region of lower concentration is called diffusion . (iii) movement of water molecules from a region of higher concentration to a region of lower concentration through a semi-premeable membrane is called osmosis .

(2) NUCLEUS : Nucleus is the control centre of the cell that contains genetic material in the form of DNA .

(3) CYTOPLASM : Cytoplasm is the jelly-like substance present between the cell membrane and the nucleus .

1. ENDOPLASMIC RETICULUM (ER) : ER ia a network of tiny tubes and sacs found in the cytoplasm of eukaryotic cells . it has two forms : Rough ER , which has ribosomes attached to its surface and is involved in protein synthesis , and smooth ER which laks ribosomes and is involved in lipid synthesis and detoxification .

2. GOLGI APPARATUS : Golgi apparatus is a complex organelle that helps in protein modification , sorting , and packaging .

3. LYSOSOMES : Lysosomes are membrane-bound sacs that contain digestive enzymes and help in cellular digestion and recycling .

4. RIBOSOMES : Ribosomes are small organelles found throughout the cytoplasm , responsible for protein synthesis .

5. MITOCHONDRIA : Mitochondria are the sites of cellular respiration , where energy is generated in the form of ATP ,.

6. PLASTIDS : Plastids are organells found in the plant cells that help in photosynthesis , storage , and synthesis of pigments .

1 . The process of cell division by which most of the cells divide for growth is called mitosis . in this process , each cell called mother cell divides to form two identical daughter cells . the daughther cells have the same number of chromosomes as mother cell .

2. Meiosis is the process of cell division that results in four daughter cells with the same number of chromosomes as the parent cell .

There are four main types of cells :

(1) Prokaryotic cells : These cells lack a true nucleus and other membrane-bound organelles . (e.g , bacteria )

(2) Eukaryotic cells : These cells have a true nucleus and other membrane-bound organelles . ( e. g , plants , animals , fungi ) .

(3) Animal cell : Animal cells are eukaryotic cells that lack a cell wall and chloroplasts . they have a true nucleus , membrane-bound organelles , and centrioles that play a roll in cell division .

(4) Plant cell : Plant cells are eukaryotic cells that have a true nucleus , cell wall , and membrane-bound organelles like chloroplasts , which are responsible for photosynthesis . they have large vacuoles for storage of water , salths , and other substances .

(1) All living organisms are composed of cells . (schleiden, 1838)

(2) cells are the basic units of life . (schwann,1839).

(3) all cells arise from pre-existing cells . (virchow , 1858) .

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