Published on March 6, 2014
The Cell Structural and Functional Unit of Life
Cell was first discovered by Robert Hooke in 1665.
What is the cell ? Structural and Functional Unit of Life. A cell is the basic unit that is capable of performing life functions.
Types of Cells Prokaryotic cell lack a nucleus or membrane-bound structures (e.g.bacteria) Eukaryotic cell have a nucleus and membrane-bound organelles (e.g.animals plants, fungi)
Prokaryotic cells Naked DNA no nuclei Few internal structures One-celled organisms, Bacteria
Structure of the Cell Mitochondria Plasma membrane Nucleus Ribosome Lysosome Vesicle Cytoskeleton Peroxisome Rough Endoplasmic Reticulum Golgi apparatus
Structure of the Cell
ISOLATION OF SUBCELLULAR ORGANELLES Homogenizationwith help of glass/teflon homogenizer cells are disrupted by- suspending in isotonic soln (0.25 M buffer at pH 7.4) Differential velocity Centrifugation. Separation based on their size.
ISOLATION OF SUBCELLULAR ORGANELLES Supernatant 960 g 10 min pellet Homogenate 25000 g 10 min pellet Nuclei DNA polymerase Supernatant 34000 g 30 min pellet Supernatant Supernatant cytosol 105000 g 100 min LDH pellet Mitochondria Golgi complex Lysosomes, Galacosyl Peroxisomes transferase ATP synthase, Acid phosphatase, catalase pellet E. Reticulum G 6 PD
Parts of the Cell Plasma membrane Nucleus Cytoplasm
Nucleus prominent and large organelle houses most of a cell’s DNA. contains genes Controls the activity of other organelles.
Structure of Nucleus a spherical or oval-shaped structure. Most cells have a single nucleus, although some, such as mature RBCs, have none. In contrast, skeletal muscle cells have multiple nuclei. the nuclear envelope, membrane of the nuclear is continuous with rough ER nuclear pores Each nuclear pore consists of a circular arrangement of proteins surrounding a large central opening
Functions 1. Controls cellular structure. 2. Directs cellular activities. 3. Produces ribosomes in nucleoli. Chromatin Polyribosome Nucleolus Nuclear envelope Nuclear pore Nuclear pore Rough endoplasmic reticulum The nuclear envelope Details of the nucleus
Ribosomes are the sites of protein synthesis. The name of these tiny organelles reflects their high content of rRNA. They either attached to RER or float freely in cytoplasm. consists of two subunits. - large subunit - small subunit.
A network of membranes in the form of flattened sacs or tubules Two types -Rough ER -Smooth ER
Nuclear envelope Ribosomes Rough ER Smooth ER
1. Rough ER synthesizes proteins. 2. RER involved in post-translation modifications such as glycation. 3. SER synthesizes phospholipids, cholesterol (in many tissue) & steroid hormones (adrenals, gonads). 4. SER is site of Glycogen metabolism. 5. Stores & releases calcium ions in the cells. (that trigger contraction in muscle cells.) 6. In liver & Kidney SER Detoxifies drugs & harmful substances; 7. Removes the phosphate group from G-6-P; and release free glucose in blood.
It consists of 3 to 20 cisternae, small, flattened membranous sacs. Most cells have several Golgi complexes Golgi complexes are more extensive in cells that secrete proteins Modifies, sorts, packages, & transports proteins received from the rough ER
Processing and packaging of proteins by the Golgi complex.
Elongated or rod shaped. “powerhouses” of the cell. No. may as few as hundred or as many as several thousand, depending on the activity of the cell. Active cells such as muscles, liver, and kidneys, which use ATP at a high rate, have a large number of Mitochondria
Mitochondria Outer mitochondrial membrane Inner mitochondrial membrane Matrix Cristae Ribosome Enzymes Function Generate ATP through reactions of ETC. Helps in Biochemical reactions. Such as oxidation of fatty acids, TCA, etc
Membrane-enclosed vesicles that form from the Golgi complex. 60 kinds of powerful digestive and hydrolytic enzymes. Lysosomal enzymes also help recycle worn-out cell structures. Helps in fertilization. Some disorders are caused by faulty or absent lysosomal enzymes. e.g, Niemann pick disease, Gaucher’s disease.
Similar in structure to lysosomes, but smaller in size. Contain several oxidases, enzymes that can oxidize various organic substances. Functions : Degradation of amino acids, oxidation of long chain fatty acids. Oxidize toxic substances, such as alcohol. protect other parts of the cell from the toxic effects of H2O2. Dysfunction of Peroxisomes leads to Zellweger syndrome
The Cytoskeleton A network of protein filaments that extends throughout the cytoplasm. Three types of filamentous proteins contribute to the cytoskeleton’s structure, Microtubules Intermediate filaments Microfilaments
The Cytoskeleton cont….. Microtubules: Long, Hollow, unbranched, polar cylinders. mead up of protein “tubulin”(α & β tubulin) The largest of cytoskeletal components.
The Cytoskeleton cont….. Microtubules: Functions:- Microtubules help in structural support, To maintain the shape of the cell. Movement of organelles such as secretary vesicles, chromosomes during cell division. Forms mitotic spindles during mitosis. Movement of cilia and flagella. Disorder: Primary ciliary dyskinesia- associated with celiary dysfunction clinical effect- recurrent upper & lower resp. tract infection, male infertility
The Cytoskeleton cont….. INTERMEDIATE FILAMENTS : Polymers of long rod like proteins. these filaments are thicker than microfilaments but thinner than microtubules. Functions :Provide mechanical support to the cell.
The Cytoskeleton cont….. Microfilament Thinnest elements of the cytoskeleton. Composed of the protein actin, Most abundant intracellular protein that that conc. Just under the plasma membrane. Most prevalent at the edge of a cell Functions : Mechanical support for the basic strength & shapes of cells. Microfilaments are involved in muscle contraction, cell division, and cell locomotion.
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