Structure Of A Cell

CELL STRUCTURE

• P.K.TESTING What is the basic unit of a wall? Brick What is the basic of unit life? Cell Define a cell. A cell is a basic structural and functional unit of life. Do you know the structure of a cell?

STRUCTURE OF A CELL Robert Hooke observed a thin slice of cork under a crude microscope. It was composed of box- like compartments, forming a honeycomb structure. He named the compartments as cells.

CORK CELL

STRUCTURE OF CELL

RECAPTULATION • • • • •

Who discovered cell? What are the main components of a cell? What is the function of cell wall? Tell the names of cell organelles. What is the function of nucleus?

• Cell mainly consists of three regions: • 1 Cell or plasma membrane - an extremely thin outer boundary of cytoplasm, • 2 Cytoplasm – a fluid jelly, transparent, often appearing granular, and • 3 Nucleus – surrounded by its own doubled walled nuclear membrane and always surrounded by cytoplasm.Cytoplasm and nucleus together constitute protoplasm.

TYPES OF CELLS • 1 In some cells, the nuclear region is not well defined as the nuclear membrane is absent. Such cells who lack a nuclear membrane are called prokaryotic cells. • 2 Those cells who possess a nuclear membrane are called Eukaryotic cells.

CELL MEMBRANE OR PLASMA MEMBRANE • It encloses the nucleus and cytoplasm of • the cell. It consists of lipids and proteins. • It is selectively permeable.

CELL WALL • It is rigid, non-living boundary wall outside the cell membrane in plant cells. Animal cells lack a cell wall. • It is made of cellulose and is permeable to water, solutes and gases. • It gives definite shape to the cell.

NUCLEUS • It is a prominent rounded structure usually located in the center of the cell. • It is the most important part of the cell, exerting a controlling influence on all cell activities. • A nucleus consists of: • Nuclear membrane • Nucleoplasm • Nucleolus • Chromatin material

NUCLEUS

CYTOPLASM • It occupies the major part of the cell. Water is the main component (up to 90%).In addition proteins, fats, carbohydrates and inorganic materials are present.

• A number of cell organelles are present in the cytoplasm. These include: • Mitochondria: It is a rod-shaped structure surrounded by a double-membrane. Energy is produced during respiration inside mitochondria. Therefore these are called “Power Houses Of The Cell”.

• Endoplasmic Reticulum: It is network of membranes which run through the cytoplasm. It is of two typesRough ER (with ribosomes) and Smooth ER (without ribosomes). Ribosomes help in protein synthesis and secretion of lipids.

• Golgi Apparatus: It consists of smooth, flattened, membrane bound, sac-like structures. It packages materials synthesized in the cell.

• Plastids: These are the largest cytoplasmic organelles found only in plant cells. These are of three types4. Leucoplasts, 5. Chloroplasts, 6. Chromoplasts. Photosynthesis is the most important function of this organelle.

• Lysosomes: • These are small spherical bodies called “Suicidal bags”. • They act as garbage disposal system of a cell.

• Ribosomes: • These are tiny membrane-less granules and are found attached to the surface of ER as well as free in the cytoplasm. They are rich in RNA and are the sites of protein synthesis in the cell.

• Vacuoles: • These are fluid-filled cavities containing dissolved food materials, waste products and pigments. • They act as store-houses of the cell.

• PRESENTED BY: • • • • •

JASWINDER KAUR SCIENCE MISTRESS G.G..Sec.School Sultanwind Amritsar.