Download Types of cells based on internal organization of cell organelles.

Cell-­‐ Its organelles, structure and Functions Definition: Cell is the structural and functional unit of living organisms. It is also called as the building block of living organism. Aggregation of cells give rise to Tissues. Definite type of tissues aggregate to form organ. Organs together form organ system. History of cell Robert Hooke (1665) First discovered cell while observing a thin piece of cork (dead bark of a tree) under his self made microscope. He observed honey comb like structures and named them cell. Robert Brown (1833) Discovered nucleus Cell Theory Jacob Schleiden (1839) All plants are made up of cell Theodor Schwann (1839) All animals are made up of cells Virchow (1855) Cells arise from pre existing cells Cell theory newly added point : Nucleic acid is the genetic material of all cells. Cells interact with each other to perform a specific function. Basic chemical composition is more or less same in all cells. Types of cells based on internal organization of cell organelles. Prokaryotic Cell No true nucleus is present. Undefined nuclear membrane, called as nucleoid. Circular called as Plasmid Folding present inside plasma membrane for cellular respiration Present. Short protein Points Nucleus Eukaryotic Cell Well defined nucleus with proper nuclear membrane DNA Mesosomes Linear with histone protein Absent Pili Absent appendages which fixes bacteria to surfaces. Both in cytoplasm and undefined nuclear region part Absent 50S and 30S Absent Single chromosome Simple binary fission Bacteria, Archaea RNA /Protein synthesis RNA synthesis-­‐ nucleus Protein synthesis-­‐ Cytoplasm Mitochindria Ribosome Chloroplast Chromosome number Cell division Example Present 60S and 40S Present More than one chromosome Mitosis, Meiosis Protists, fungi, plants, animals Unicellular Organism : Organism which is formed of a single cell, i.e, capable enough to perform all the functions for survival. Example: Amoeba sp, Chlamydomonas sp. Figure: Multicellular Organism : Organism which is formed of more than one cell of different types. Example: Higher animals. Figure: Cellular components of a cell Cell Membrane : • It provides protection to cell. • The outer covering of both • Selectively permeable to prokaryotic and eukaryotic cells substances. have a double layered membrane • Flexibility of cell membrane or that surrounds the inner plasma membrane helps some cytoplasm. organism to feed.. Example : • The membrane is Endocytosis in Amoeba. phosphorus(polar)-­‐ lipid bilayer (hydrophobic –non polar)-­‐ Phosphorus (polar layer). • Two types of proteins: integral and trans-­‐membrane proteins are present in between. Fluid Mosaic Model Cell membrane is not static. The lipids are connected to each other by very weak bonds and phospholipid bonds between lipids and phosphors is also not stable. So they tend to move and gives flexibility and fluidity to the membrane. Proteins are present like mosaic pattern outside (peripheral protein) or embedded inside the membrane as transmembrane. Thus cell membrane is flexible and this was postulated by Singer and Nicholson. Cell Wall ( Present in plant cell): • Tough ,rigid and nonliving covering present outside the cell membrane of plant cell • There are -­‐ primary cell wall (growing cell wall); Secondary cell wall(mature cell) • Between two adjascent cells cell lamella is present. • Cell wall is primarily composed of lignin, cellulose and pectin. • Plasmodesmata connects cytoplasm of adjascent cells through tiny holes present on cell wall. Cytoplasm (Cyto means cell and ‘plasma’ means fluid) • Living jelly like viscous substance (80%) present inside the cell membrane • Cell organelles are embedded in cytoplasm. • It provides rigidity, shape and structural strength to the cell. It is permeable and allows substances to pass through. Contains dissolved substances necessary for cell. It controls the shape of the cell. It is the site of manufacture of different materials needed for cell. It helps in transportation of nutrients and metabolites Nucleus (Brain of the cell) • Spherical or oval prominent structure present in cytoplasm. • Contains fine thread like structures DNA in form of chromatin reticulum. During cell division it changes to chromosomes • Contains double walled nuclear membrane. • Contains dense network structure called nucleolus( site of RNA synthesis and Ribosomes) • Contains fluid like substance nucleoplasm. • Contains nuclear pore through which proteins can enter and leave the nucleus. Ribosomes ( Protein factory) • Produced by nucleolus and is composed of both RNA and protein; smallest organelle of cell. • Normally gets attached with the walls of endoplasmic reticulum. • It has two subunits depending upon the ability of sedimentation on a special gel and is expressed as Svedberg unit.: smaller sub unit read the m-­‐RNA , bigger subunit joins the corresponding amino acid with m-­‐RNA to form In unicellular organism it helps in engulfing food. Controls all the functions of cell with the help of gene present in DNA. Site of synthesis of RNA and Ribosomes. Site of cell division. Protein synthesis (translation) Proteins synthesized by bound ribosomes are transported out side. polypeptide chain. • Amino acids are joined at the rate of 200 per minute. *** in 2009 , Indian origin Venkatraman Ramakrishnan along with Thomas A Steitz and Ada E Yonath received Nobel prize in Chemistry for determining detail structure of and mechanism of ribosome. Endoplasmic reticulum ( Site of protein and lipid synthesis) • Complex network of parallel tubular structure concentrically arranged around the nucleus. • Tubular structures are called Tubules and sac like structures are called cisternae. • Synthesized ribosomes in nucleus if gets attached to ER, forms Rough Endoplasmic reticulum (RER) and ER with out risomoes are called Smooth Endoplasmic reticulum ( SER). Golgi Body (Discovered by Camellio Golgi) • Parallel sacs present in concentric pattern either around the nucleus or is continuous with endoplasmic reticulum. • Fluid filled sacs are called cisternae. Tube like structures are called Tubules. • Region facing nucleus is called Cis phase; region facing away from nucleus is called Trans-­‐ phase. RER forms protein SER forms lipids. SER also detoxify harmful substances in the cell. It acts as a passage for transfer of substances with in and outside the cell. It also acts as a packaging site where proteins are modified before transporting to other parts of the cell. Lysosomes (Suicidal bag of cell) Helps in removal of old and dead cells. present only in animal cell. Digest foreign invading organism and break them into smaller pieces. • Membrane bound vescicles containing digestive enzymes. Vacuoles Stores important materials formed • Membrane bound sacs present with in the cell. both in plant and animal cells. • The membrane of vacuole is Provides rigidity to plant cell. called tonoplast. Mitochondria (Power house of cell) Site of synthesis of ATP by aerobic respiration • Double membrane structure; outer smooth layer and inner membrane with fold forming cristae. • Cristae forms ground substance called matrix • ATP synthase, mitochindrail DNA are present in the matrix Chloroplastid ( Present only in green Site of synthesis of glucose and it is plants) stored as starch. • Double membrane structure containing ground substance called stroma. • Sac like structure thylakoid are present in stroma. Thylakoid forms Granum which are connected with lamella. Some animal cells also posses cilia and flagella.