BS311 Cell Biology PDF

BS311 Cell Biology Dr. Mandar Kulkarni PDPIAS, CHARUSAT  Syllabus 1. Cell as a basic unit of life 2. Bio-membranes of cells 3. Cell organelles and special structures of cells 4. Cytoskeleton and extracellular matrix 5. Cell-cell interactions 6. Cell...

BS311 Cell Biology Dr. Mandar Kulkarni PDPIAS, CHARUSAT  Syllabus 1. Cell as a basic unit of life 2. Bio-membranes of cells 3. Cell organelles and special structures of cells 4. Cytoskeleton and extracellular matrix 5. Cell-cell interactions 6. Cell cycle, cell death and cell renewal 7. Tools and techniques of cell biology Unit 1: Cell as basic unit of life Overview of cellular evolution and cell theory Comparison of prokaryotic and eukaryotic cells- cell size, shape and structural differences Special cells like neurons and muscle cells Basic molecules of a cell Fundamental functions of cells  What is a cell ? The smallest structural and functional unit of an organism, which is typically microscopic and consists of cytoplasm and a nucleus enclosed in a membrane. A unit of biological activity delimited by a semipermeable membrane and capable of self-reproduction in a medium free of other living systems.  Cell Simplest integrated organisation in living systems, capable of independent survival. Plant Stem Amoeba Proteus Red Blood Cell Bacteria Nerve Cell  Cell theory All living organisms are made up of one or more cells and cell products All metabolic reactions in unicellular and multicellular organisms takes place in cells Cells originate from other cells The smallest clearly defined unit of life is the cell Their microscope had two lenses and total magnifying power between 10X and 30X Called Flea glasses. (Fleas - insect) Book - Micrographia 300X He was the first to observe living free cells. His sketches included numerous bacteria (bacilli, cocci, spirilla), Protozoa, Hydra -movement of blood cells Schleiden was the first to describe the nucleoli and to appreciate the fact that each cell leads a double life—one independent, pertaining to its own development, and another as integral part of a multicellular plant. his work with the connective tissues such as bone and cartilage led him to modify the evolving cell theory to include the idea that living things are composed of both cells and the products or secretions of the cells. Schwann also introduced the term metabolism to describe the activities of the cells. Characteristics of true cells All kinds of true cells share the following three basic characteristics: 1. A set of genes which constitute the blueprints for regulating cellular activities and making new cells. 2. A limiting plasma membrane that permits controlled exchange of matter and energy with the external world. 3.A metabolic machinery for sustaining life activities such as growth, reproduction and repair of parts.  Exception of the cell theory Viruses Are Biologists’ Puzzle. They There Are Certain Other Are An Exception To Cell Theory. They Organisms That Contain More Lack Protoplasm, The Essential Part Than One Nucleus Of The Cell. Uses the metabolic machinery of hosts. primitive organisms that have not reached a cellular state.” Two types of cells Hans Ris in 1960’s suggested these terms Prokaryotic and Eukaryotic. Prokaryotic cells Prokaryotic cells  Prokaryotic cells Primitive or before Karyon Nucleus Cells with primitive nucleus Prokaryotic cells Small One envelope system Simple Most primitive – Came into existence perhaps 3.5 billion years ago E.g. The stromatolites (colonies of extinct cyanobacteria) of Western Australia Examples: Bacteria, Archea, Mycoplasma, Blue-green algae Structure of prokaryotic cell Plasma membrane Live, ultrathin (6-8 nm) Dynamic Covers the bacterial protoplasm Lipid bilayer with embedded proteins, follows fluid-mosaic pattern 1. Plasma membrane Function ? 1. Plasma membrane Plasma membrane is attached to DNA Why? In prokaryotic cells, DNA is present at which location/area? Plasma membrane intrusions Infoldings of the plasma membrane gives rise to these structures Recorded in all Gram positive bacteria and some Gram negative bacteria 1. Mesosomes 2. Chromatophores a. Mesosomes Extension of plasma membrane within the cell, complex whorls of convoluted membranes Increase the plasma membranes surface which is in contact with cytoplasm E.g. Chemoautotrophic bacteria like Nitrosomonas E.g. Photosynthetic bacteria like Rhodopseudomonas Also involved in cross wall septum formation during cell division b. Chromatophores Similar to mesosomes Shape is different as compared to mesosomes Observed as vesicles, tubes, bundled tubes, stacks Bear photosynthetic pigments 2. Cytoplasm Hyaloplasm/matrix/cytosol Ground substance All metabolic activities Components – water, proteins, lipids, carbohydrates, RNA, other metabolites and molecules 2. Cytoplasm A less dense area – Where? Cytoplasm – also contains Why? reserve material in bacteria 1. Finely dispersed Dark or dense area – Where? 2. As inclusion bodies Why? a. Volutin/metaphosphate granules b. Hydrogen sulphide droplets c. Poly β-hydroxybutyrate granules Can we stain animal cells with crystal violet? 3. Nucleoid Bacterial genome/bacterial chromosome Single, circular and double stranded DNA Not separated from cytoplasm by nuclear membrane The whole DNA is concentrated in a specific clear region in cytoplasm, called nucleiod No ribosomes in nuceloid No nucleolus in nucleoid  3. Nucleoid DNA is attached to plasma membrane at one site. Therefore when DNA is isolated from prokaryotic cells it carries number of membrane components with it. No histone proteins are recorded, instead small heat stable (HU) proteins are found. All classes of RNA (i.e. mRNA, tRNA, rRNA) are transcribed by single RNA polymerase. mRNA formed is directly available for translation (no mRNA splicing) and therefore transcription and translation can go hand in hand/simulteneously. 4. Ribosomes Size: 25 nm Composed of: rRNA + proteins Site for protein synthesis Bacterial ribosomes are 70s type (which are the two subunits?) Non-functional ribosomes are present as separated subunits in cytoplasm Polyribosomes/polysomes Ribosomes in cytoplasm Ribosomes attached to plasma membrane 5. Plasmids Many species of bacteria may carry plasmids and many species may not. These are extrachromosomal genetic elements - small, circular and closed DNA molecules Some plasmids are bacteriophage DNA which may eventually incorporate in the bacterial chromosome Some plasmids are separated parts of the genome for the same or foreign cell, an may recombine with the main chromosome 5. Plasmids - functions Colicins: These plasmids produce antibiotically active proteins. (Why?) Fertility factor: These plasmids act as fertility factors ('F' factor) which stimulate bacterial conjugation Resistant factor: These plasmids produce enzymes and proteins with confer resistance to one or more drugs or antibiotics. ('R' factor) 6. Cell wall In prokaryotes except for mycoplasma, the cell membrane is covered by strong and rigid cell wall. Provides mechanical protection and characteristic shapes. Different from that of plant cell wall (what is the difference?) Cell wall of Gram-positive and Gram-negative bacteria How to perform Gram- staining? 7. Capsule In some bacteria cell wall is further surrounded by additional slime or gel. It is thick, gummy and mucilaginous substance secreted by plasma membrane. Functions Confers protection against phagocytosis and viruses Helps in transport of ions and water. 8. Flagella Possessed by motile bacteria e.g. E. coli 15-20 nm in diameter and up to 20 µM long May be one or more Made up of flagellin Attached to plasma membrane by hook Rotates like a propeller of ship Flagellation pattern 9. Fimbriae or pili Mostly Gram-negative bacteria contain non-flagellar extremely fine appendages celled fimbriae or pili. Non-motile Adhesive structures (meaning?) Pili – conjugation (F-pili or sex-pili) 10. Spinae Some Gram-positive bacteria have tubular, pericellular, rigid appendages of single protein moiety Spinin Spinae Help to tolerate adverse environmental conditions e.g. Salinity 11. Reproduction in prokaryotes Binary fission Conjugation 12. Forms in bacteria Eukaryotic cells  Eukaryotic cells Well developed Karyon Nucleus Cells with well-developed nucleus Eukaryotic cells Essentially two envelop system Much larger than prokaryotic cell Secondary membrane envelopes the nucleus and other internal organelles and to a great extent it is present throughout the cytoplasm as endoplasmic reticulum From algae – higher plants From protozoa – higher animals Eukaryotic cells Videos… A typical animal cell A typical plant cell Basic molecules of cell  Introduction The branch of science The branch of biology that concerned with the deals with the structure chemical and physico- and function of the chemical processes and macromolecules (e.g. substances that occur proteins and nucleic acids) within living organisms. essential to life.  Comprised of multitude of non-living constituents, this includes: Proteins Nucleic acids Fats Protoplasm Carbohydrates Vitamins Minerals Waster metabolites Crystalline aggregates Pigments and many others Protoplasm and cytosol Protoplasm Cytosol Protoplasm is alive because of Cytoplasmic matrix or cytosol is the highly complex organisation the fluid and soluble portion of of these non-living substances cytoplasm that exists outside the and the way they interact with organelles. each other.  Colourless or greyish Translucent Viscous Gelatinous or jelly-like colloidal Physical substance nature of Heavier than water Capable of flowing cytosol Some physical characteristics of cytosol have been debated for a long Chemical nature or organisation of cytosol Of the 92 naturally occurring elements, about 46 are present in cytosol Of which 24 are essential for life Six are crucial for living system Five are essential Trace elements  Carbon – 20% Hydrogen – 10% Nitrogen – 3% Super six Oxygen – 62% Phosphorous – 1.14% Sulphur – 0.14%  Calcium – 2.5% Potassium – 0.11% Essential five Chlorine – 0.16% Magnesium – 0.07% Sodium - 0.10% Trace Iron Vanadium elements Iodine Silicon Molybdenum Nickel Zinc Fluorine Selenium Boron Copper Manganese Cobalt Chromium  Cytosol has various kinds of ions, which are important for maintaining osmotic pressure and acid- base balance in the cells (Electrolytes) Mg++ K+ Ions Na+ Cl- Ca++ Concentration of K+ and Mg++ is high inside the cell and concentration of Na+ and Cl- is high outside the cell  Buffering system – blood – H2PO4- Buffering system – cytosol – HPO4- Ions Non-electrolytes: Minerals in non-ionising state, act as cofactors, important for metabolism e.g. Mo, I, Fe. Types of compounds in cytosol Compounds Organic (30%) Inorganic (70%) Composition Water = 65% Protein = 18% Fat = 10% Carbohydrates = 5% Other organic compounds = 1% Other inorganic compounds = 1% Inorganic compounds Water Minerals Salts  Carbohydrates Proteins Organic Lipids compounds Vitamins Hormones Nucleic acids Fundamental functions of cell Functions of cell 1. Provide structure and support: Fundamental units of life, structural basis of all organisms, e.g. xylem, skin, bone 2. Facilitate growth through mitosis: Growth of tissues, organs and individuals depends on cell division i.e. mitosis Functions of cell 3. Allow active and passive transport: Import and export nutrients for various use in various biochemical reactions a. Passive transport occurs by using gradient and not energy is required (simple molecules) b. Active transport occurs with or against the gradient, but energy is used (complex molecules) Functions of cell 4. Produce energy: Cells produce energy by using process called respiration wherein complex energy yielding molecules are broken down to yield energy Mitochondria The cellular energy is used by the organism Functions of cell 5. Create metabolic reactions All Bio-chemical reactions occur in cell Anabolic reactions Catabolic reactions 6. Aids reproduction Mitosis: asexual Meiosis: sexual