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A Brief Overview of a Living Cell

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    All organisms are made up of cells. The cell is the simplest collection of matter that can live, Cell structure matches its function. All cells are related by their descent from earlier cells, Cells can differ substantially from one another but share a common feature.

    overview of animal cell

    How Do We Look At the Cell:

    To study cell biologist use microscope and tools of Biochemistry


    In a Light Microscope visible light passes through the specimen and then through glass lenses, which magnify the image

    parameters of microscope includes Magnification, resolution and contrast


    Ratio of an object’s image size to its real size, Light microscope can magnify 1000 times the actual size of the specimen

    The resolution defined the clarity of the image, the light microscope provides high definition image with clarity

    Electron Microscope :

    This focuses a beam of electrons instead of light . Following are the types of Electron Microscope

    Transmission Electron Microscope: send electron beam though the sample surface to see images that Look 3D

    Scanning Electron Microscope: Send an electron beam on the specimen to see inside the cell.

    Cell Fraction: This process takes cells apart to separate the major Organelles from one another

    Ultracentrifuges fractionate cells into their component parts

    human skin cell under microscope

    Types of cells:

    There are 2 types of cell . Prokaryotic + Eukaryotic

    prokaryotic: prokaryotic cell does not contain any nucleus, DNA is present in the form of a loop freely in the cytoplasm, it also has extra DNA called plasmid it’s circular in shape and have no membrane-bounded organelles and they are smaller in size e.g., Bacteria

    Eukaryotic cell: contains a true nucleus, membrane-bounded organelles, large in size, E.g. plant cell, Animals cell, Fungi cells.

    Features that are common in both cells are cytosol, chromosome, plasma membrane, and Ribosome.

    Plasma Membrane: Cell is guarded and surrounded by a plasma membrane, A selective barrier that allows sufficient passage of oxygen, nutrients, and waste to service the cell. following are the parts of Eukaryotic cell.

    Plasma membrane, Nucleus, Endoplasmic Reticulum, Golgi Apparatus, lysosomes and vacuoles.

    The nucleus is the information cell. it contains the cell genes and surrounded by a double membrane structure: the nuclear envelope. Genetic material is inside the nucleus. DNA and Proteins form genetic material called chromatin. Chromatin condenses to form chromosomes.

    Another structure inside the cell called NUCLEOLUS is present that synthesize Ribosomal RNA. Ribosomes are the protein factories they carry out protein synthesis in two locations.1) In cytosol ( free ribosomes)and on 2) endoplasmic reticulum ( bound ribosomes). The endoplasmic reticulum is the biosynthetic factory there are two types smooth and rough. smooth has no ribosomes it synthesizes lipids, metabolizes carbs, detoxifies poisons stores calcium. Rough endoplasmic reticulum has bound ribosomes which secrete glycoproteins and distributes transport vesicles.


    The Golgi Apparatus is the shipping and receiving center it contains flattened membranous sacs called Cisternae it modifies products of the Endoplasmic reticulum, manufactures certain macromolecules, sorts and packages material into transport vesicles. Lysosomes are the Digestive compartments. These are the sacs that contain hydrolytic enzymes that can digest proteins, fats, and polysaccharides, and nucleic acids. it fuses with a food vacuole to digest the molecules. it can have enzymes to self destroy the cell “Autophagy“. Vacuoles are the diverse maintenance compartments. A plant cell contains a large vacuole that is situated in the center of the cell. there are further types of vacuoles, Food vacuoles that are formed by phagocytosis, Contractile vacuoles that pumped excess water out of cells, and central vacuoles that hold organic compounds and water.

    TEM view of Golgi apparatus

    Mitochondria are the sites of cellular respiration, a metabolic process that generates ATP. these are double membrane-bounded organelles, have proteins made from free ribosomes, and contain their own DNA. Mitochondria have a smooth outer membrane and inner folded membrane into cristae to increase surface area. the inner membrane contains intermembrane space and mitochondrial matrix. Chloroplast found in plants and algae and is the site of photosynthesis. it contains green pigment for photosynthesis, it found in leaves and other green parts of plants and algae.

    Role of the cytoskeleton: it provides support to the cell and maintains its shape. it interacts with motor proteins to produce motility. Inside the cell, vesicles can travel along with monorails provided by the cytoskeleton. Following are the components of cytoskeleton.


    Microtubules are thickest hollow tubes wall consist of 13 columns of tubulin molecule its diameter is 25nm with 15 nm lumen its protein subunit is tubulin . Its main function is maintenance of cell shape , cell modality , chromosome movements in cell division and aid in organelle movements

    Microfilaments are thinnest and forms by two intertwined strands of actin. its diameter is 7nm. Protein subunits are Actin. its main functions are maintenance of cell shape , Muscle contraction , cytoplasmic streaming movement , cell motility and cell division.

    Intermediate filaments have a diameter between both. it forms from the fibrous proteins supercoiled into the thicker cable. its diameter is from 8 to 12 nm. its protein subunits are keratin family. its main functions are maintenance of cell shape, Anchorage of the nucleus, and several organelles, and formation of the nuclear lamina. The centrosome is formed from microtubules when they grow out near the nucleus. it has a pair of centrioles, each with nine triplets of microtubules arranged in a ring

    Extracellular components: these helps co ordinate cellular activities. it includes cell walls in plants and extracellular matrix ECM in animal cell

    Cell wall: only found in plants some prokaryotes and fungi. helps to protect plant cells and maintain shape. it made up of cellulose fiber, polysaccharides, and proteins. it has 3 layers primary cell wall that is relatively thin and flexible, a Middle cell wall that is present between the primary walls of the adjacent cell, and the Secondary cell wall present between the plasma membrane and the primary cell wall.

    primary secondary and middle cell wall
    cell wall in plant cell

    ECM of animal cells is made up of glycoproteins such as collagen, peptidoglycans, and fibronectin. ECM proteins bind to receptor proteins in the plasma membrane called integrins

    Functions of ECM includes Support, Adhesion, Movement, and regulation.

    Content writer : Zareen Tariq (Zoologist).

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