Cell stucture and function class 8
- 1. CELL STUTURE AND FUNCTION This Photo by Unknown Author is licensed under CC BY-SA-NC
- 2. CELL Cells are the fundamental structural units of living organisms and the basic units of life. Robert Hooke discovered the cell in the year 1665 from a thin section of cork under a self-made microscope.
- 3. CELL PARTS
- 4. PROKARYOTIC & EUKARYOTIC CELLS • Prokaryotic – Size: generally small ( 1-10 µm) Where 1 µm = 10 −6m. • The nucleus is not well defined and known as a nucleoid. • Single, circular chromosome. • Membrane-bound organelles absent. Eg: Bacterial cell • Eukaryotic – Size: generally large ( 5-100 µm). • The nucleus is well defined and surrounded by a nuclear membrane. • Possess more than one and linear chromosome. • Membrane-bound cell organelles are present. Eg: Human cell.
- 5. CELL MEMBRANE • Cell membrane • The cell membrane separates cells from one another and also the internal contents from the surrounding medium. • It is porous and allows the movement of substances or materials both inward and outward.
- 6. CYTOPLASM Cytoplasm •It is the jelly-like substance present between the cell membrane and the nucleus. •Various other components, or organelles, of cells are present in the cytoplasm.
- 7. CELL WALLS • Cell walls in plants • A cell wall is an additional covering over the cell membrane in plant cells. • It gives shape and rigidity to these cells. • It gives a rigid structure to plant cells and that is why they can withstand the stress of high-velocity wind, rain, high temperature etc.
- 8. NUCLEUS Nucleus •It is generally spherical and located in the centre of the cell. •The nucleus is separated from the cytoplasm by a membrane called the nuclear membrane. •It uses information in the chromosomes to decide what each organelle should do and the functions of the cell. •The nucleus contains an even smaller concentrated material called nucleolus.
- 9. VACUOLES Vacuoles •Vacuoles are storage bubbles of irregular shapes which are found in cells. •The vacuole stores the food, a variety of nutrients that a cell might need to survive or waste. •In plant cells, vacuoles are much larger than in animal cells and they provide rigidity to the plant cells.
- 10. GOLGI APPARATUS AND ENDOPLASMIC RETICULUM • Golgi Apparatus also termed as Golgi Complex is a membrane-bound nucleus. • Its main function is to modify proteins. • These modified proteins are placed in Golgi so that it can transport elsewhere in the cell when required. • Endoplasmic Reticulum • It is a membranous organelle. • It is found in all eukaryotic cells. • The ER is divided into two types based on their physical and functional properties viz. Smooth and Rough ER.