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Biology Chapter 2

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Biology 1201A

Biology Notes Chapter 2 The Cell An Overview Pages 2547Why It Matters HookeRobert looked at a thinly sliced cork from a mature tree through a microscope and observed tiny compartments that he called rooms in latin cellulae where the name cell came from He was looking at walls of dead cells mid 1600sAnton van Leeuwenhoekobserved moving animalcules using a singlelens microscope of his own He discovered protists sperm cells and bacteria late 1600sRobert Brownobserved spherical body inside some cells and called it a nucleus 1820sMathias Schleidentheorized that the nucleus had something to do with the development of the cell 1838Theodor Schwannproposed that all animals and plants consists of cells that contain a nucleus Rudolf Virchowproposed that cells arise only from preexisting cells by a process of divisionCell Theory 19th century1 All organisms are composed of one or more cells2 The cell is the basic structural and functional unit of all living organisms3 Cells arise only from the division of preexisting cells21 Basic Features of Cell Structure and FunctionCellscontain highly organized systems of molecules such as nucleic acids DNA and RNA contain hereditary information direct the manufacture of cellular moleculesmake energy using chemical reactions from light sourcesUnicellular organisms almost all bacteria and archaea some protists such as amoebae some fungi such as yeastLife as we know it does not exist in units simpler than individual cells21A Cells are small and Are Visualized Using a MicroscopeAll forms of life are grouped into one of three domainsBacteriaArchaeaEukaryasmallest bacteria is 05um micrometers one thousandth of a millimetre1m102cm103mm106um109nmMicroscopy a technique for producing visible images of objects biological or otherwise too small for the human eye microscope is the instrument usedLight Microscopes use light to illuminate the specimenElectron Microscopes use electrons to illuminate the specimen have higher resolution due to shorter wavelengthMagnification the ratio of the object as viewed to its real size exp 12003Resolution the minimum distance by which two points in the specimen can be separated and still seen as two points It depends on the wavelength of the light or electrons used to illuminate the specimen the shorter the wavelength the better the resolutionCells are all different size based on their their own functional capability There comes a point when a cell can no longer increase in size to retain more nutrients from more surface area to supply the volume and area inside that is why cells can only get so bigDifferent types of microscopes are described on page 28
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