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A View of the Cell The Discovery of Cells p.171-174 The History of the Cell Theory • Before microscopes were invented, people believed that diseases were caused by curses + supernatural powers • Microscopes opened the world to microorganisms • Microscopes enabled scientists to study cells – the basic unit of living things Light Microscopes • 1600s – Anton van Leeuwenhoek – Made the first microscope • Compound Light Microscope – Uses a series of lenses to magnify objects – Can magnify up to 1500x Compound Light Microscope The Cell Theory • Robert Hooke – English scientist – Studied cork – dead cells of oak bark – noticed repeated geometric boxshaped structures – called them CELLS The Cell Theory • Several scientists extended Hooke’s observations and came up with important conclusions – Schleiden • – Botanist – concluded that plants were made up of cells Schwann • Zoologist – concluded that animals were made up of cells The Cell Theory • The observations + conclusions of these scientists are summarized as one fundamental idea of modern biology – the Cell Theory: – All organisms are composed of one or more cells – The cell is the basic unit of structure + organization of organisms – All cells come from preexisting cells Electron Microscopes • 1930s + 1940s – electron microscope was developed • Uses a beam of electrons to magnify objects up to 500,000x the original size • Specimens must be viewed in a vacuum • Disadvantage? – Cannot use living specimens Two Types of EMs • Scanning Electron Microscope (SEM) – Scans surface features – Creates a 3-D image • Transmission Electron Microscope (TEM) – Capable of seeing internal cell structures Two Basic Cell Types • All cells contain small, specialized structures called organelles – Many are surrounded by membranes – Each has a specific function in the cell Prokaryotes • Cells that do not contain any membranebound organelles • Many are unicellular organisms, such as bacteria Eukaryotes • Cells that contain membrane-bound organelles • Many are multicellular but some may be unicellular, such as yeasts or amoebas Prokaryote vs. Eukaryote • Organelles benefit eukaryotic cell – Separates chemical reactions inside the cell so many can happen at one time • Robert Brown+ Rudolf Virchow – Observed a prominent structure inside the eukaryotic cell that is responsible for cell division • Nucleus – Central membrane bound organelle that manages or controls cellular functions – AKA – “the brain of a cell”