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Lecture 1:Cell Theory

Lecture 1:Cell Theory. Cell theory vs spontaneous generation Prokaryotic and Eukaryotic cells Microscopes the invaluable tools The plasma membrane Cell organelles. Reference Text: The World of the Cell by Becker, Kleinsmith & Hardin 6 th edition. Discovery of Cells.

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Lecture 1:Cell Theory

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  1. Lecture 1:Cell Theory • Cell theory vs spontaneous generation • Prokaryotic and Eukaryotic cells • Microscopes the invaluable tools • The plasma membrane • Cell organelles

  2. Reference Text: The World of the Cell by Becker, Kleinsmith & Hardin 6th edition

  3. Discovery of Cells • 1665: the name ‘cell’ coined by Robert Hooke from microscopic observation of plant cork cells (dead) • 1674: Antonie van Leeuwenhoek first to observe living cells (spirogyra)---animacules • 1828: Robert Brown observed and named the ‘nucleus’ (plant epithelial cells) • 1839: Purkinje first to name ‘protoplasm’ • 1839: Schleiden and Schwann credited for the ‘Cell Theory' and Rudolf Virchow accounted for ‘cell division’ in the formation of tissues.

  4. Where Do Cells Come From? • The cell theory states that all organisms are made of cells • Cells comprise the basic unit of structure for all organisms • Louis Pasteur proved that all cells arise from pre-existing cells • Single-celled organisms in a population are related to a single common ancestor, and • All cells in a multicellular organism alsodescend from a single ancestral cell • Cells do not arise by spontaneous generation

  5. Pasteur’s Experiments show that cells arise from other cells (not spontaneously).

  6. Robert Hooke and Anton van Leeuwenhoek • the first to observe cells in the late 1660s. • Cells consist of a membrane that contains • concentrated chemicals dissolved in water. • Are All Organisms Made of Cells? • Depends on what you call an organism, some call viruses • microorganisms, but the structure of viruses is not based on • the cell, viruses are acellular

  7. Two Cell Types 1.Prokaryotic cells:do not contain a true nucleus eg bacterial cells 2. Eukaryotic cell:contain a prominent membrane bound true nucleus eg plant, fungal and animal cells

  8. The EM An essential Tool • SEM scanning electron microscope : samples are scanned with a beam of high energy electrons producing a 3-D image as they interact with molecules in the sample and are reflected. • Use for surface features • TEM transmission EM produces an image with electrons that pass through the specimen.Detected on a flourescent imaging screen • Use with ultra-thin sections

  9. The Plasma Membrane

  10. Phospholipid Bilayers • In water, phospholipids spontaneously form micelles or lipid bilayers • They have polar phosphate "heads" that face outward • And hydrophobic fatty acid "tails" that face inward toward other tails

  11. glycerol Lipid bilayer

  12. Phospholipids in Detail Polar Chemical groups with an uneven distribution of electrons that allows it to take part in electrostatic interactions and form eg H bonds Non Polar Chemical groups with a uniform distribution of electrons that is unable to interact with other groups.

  13. lipid bilayer (cell membrane) 7-8 nm (7-8 x10-9m)

  14. The fluid-mosaic model of membrane structure • suggests that some proteins are inserted into the lipid bilayer • This makes the membrane a fluid, dynamic mosaic of phospholipids and proteins

  15. Fluid-mosaic model

  16. Lipid BilayershaveSelective Permeability • Small or nonpolar molecules move across phospholipid bilayers quickly • charged or large polar substances cross slowly, if at all. • Thus, phospholipids bilayers have selective permeability

  17. selective permeability

  18. Two Cell Types 1.Prokaryotic cells:do not contain a true nucleus eg bacterial cells 2. Eukaryotic cell:contain a prominent membrane bound true nucleus eg plant, fungal and animal cells • Acellular ‘life’structure is not based on cells eg • Viruses nucleic acid and protein • viroids naked RNA (no protein) • Prions infectious protein (no nucleic acid)

  19. Bacterial cells are prokaryotic

  20. Animal Cells Are Eukaryotic

  21. Plant Cells are Eukaryotic

  22. Cellular components can be separated into fractions according to size Requires a centrifuge

  23. How a centrifuge works

  24. Cell Fractionation

  25. Cell Fractionation

  26. Smaller organelles

  27. Cellular compartments and Organelles • Nucleus • Rough Endoplasmic Reticulum • Smooth Endoplasmic Reticulum • Mitochondrion • Lysosomes

  28. nucleus

  29. Rough endoplasmic reticulum

  30. Smooth endoplasmic reticulum

  31. mitochondrion

  32. lysosome

  33. The Cell Theory Summary • All organisms are made of cells • Cells comprise the basic unit of structure • for all organisms • All cells come from pre-existing cells.

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