Cells as Experimental Models
E. coli , Yeasts , Dictyostelium discoideum , Caenorhabditis elegans, Drosophilia melanogaster
Arabidopsis thaliana , Vertebrates
Tools of Cell Biology: Light Microscopy, Electron Microscopy
Subcellular Fractionation
Growth of Animal Cells in Culture, Culture of Plant Cells
Viruses
Origin and Evolution of Cells:
Both Prokaryotes and Eukaryotes originated from a common single ancestor. First Cell is believed to have arisen as a result of enclosure of self-replicating RNA by phospholipid membrane about 3.5 to 3.8 billion years ago.
Stanley Miller demonstrated in 1950 the spontaneous formation of organic molecules by subjecting electric discharge to a mixture of H2, CH4, NH3 and H2O.
Evolution of Metabolism: Earliest organism obtained metabolic energy through a form of anaerobic glycolysis.
ATP generations are thought to have evolved in three stages; corresponding to the evolution of glycolysis, photosynthesis, and oxidative metabolism.
Prokaryotes have two division: Archaebacteria-which are progenitors of the most primitive bacteria and Eubacteria-modern day bacteria
Eukayotic Cells: Larger and more complex than Prokaryotes with its nucleus, cytoplasmic organelles and cytoskeleton, which are believed to have evolved from symbiotic association of prokaryotes (Endosymbiosis).
Cytoplasmic organelles:
Mitochondria and Chloroplast- Play very critical role in energy metabolism. Both organelles have DNA. Mitochondria is the site of oxidative metabolism and responsible for generating most of the cellular ATP.
Chlroplast- Site of Photosynthesis and found only in green plants and algae.
Lysosome and Peroxosome: Specialized metabolic compartment for digestion of macromolecules and many oxidative reactions.
Peroxisome- Involved in metabolism of H2O2, lipids and carbohydrate.
Vacuole- Digestion of macromolecules, storage of waste products, mostly found in plants.
Endomembrane System:
Rough endoplasmic raticulum-Synthesis and processing of protein.
Smooth Endoplasmic raticulum- Synthesis and processing of lipids, detoxification.
Golgi apparatus: Process, sort and transport protein, lipids and carbohydrates to their final destination. In plant cells serve as site for lipid synthesis and also polysaccharide synthesis for cell wall.
Multicellulor Organism:
Plants- Composed of fewer cell types compare to animal. Three main tissue system in plants-Parenchyma Cells- Carry out most of the metabolic reactions
Ground Tissue-Collenchyma and Sclerenchyma-Thick cell walls and provide structural support to plants.
Epidermal Cells- Protective covers and allows absorption of nutrients.
Animal-Human Body-200 different types of cells. Five different Tissue Types: Epithelial-Covers surface of body and line internal organs.
Connective Tissue-Bone, Cartilage, Adipose tissue formed by different types of cells such as Osteoblast, Chondrocytes, adipocytes, fibroblast.
Blood-Function in Oxygen Transport (Erythrocytes), Immune response (Granulocytes, Monocytes and Macro phages)
Cells as Experimental Model:
E.Coli- Genetic simplicity, easy to grow, regenerates and manipulates. Use for study of basic aspects of molecular biology and biochemistry.
Yeasts- Simplest eukaryote. Model for investigating eukaryotic cell biology,
Dictyostelium discoideum- Single cell eukaryote, use for studying cell movement.
Caenorhabditis elegans- Nematode, simple muticelluor organism useful as a model for developmental biology.
Drosophila melanogaster- Short generation time. Easy to manipulate, provided major clues in understanding animal development.
Vertebrates- Xenopus laevis-important model for studies of early vertebrate development.
Mouse- Mammalian species suitable for genetic analysis.
Cell Culture:
Animal Cell: H. eagle 1955 first developed defines cell culture media.
Primary Cell Culture- Starting culture established from a tissue. Usually grow until culture dish surface is covered (Confluent Growth).
Immortal Cell Line- Cell culture derived from tumors proliferate indefinitely.
Plant Cell-Totipotency- cultured plant cell can differentiate to form specialized cell types, in some cases regenerate to produce whole plants.
Viruses:
Intracellular obligate parasites. Can be cultured only in living cells. Viruses consist of a nucleic acid core (DNA or RNA) and a protein cover.
Retroviruses- Family of RNA containing animal viruses containing reverse transcriptase which can synthesize a DNA copy of its genome.
Bacteriophage-Viruses that parasitize viruses.