Ch3_Structure and Function

Ch3_Structure and Function - CELL STRUCTURE AND FUNCTION...

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CELL STRUCTURE AND FUNCTION *All living entities are composed of cells *To understand disease and how to fight it we must understand the structure and function of cells *To understand how pathogens attack us and our cells and how we defend against them, we have to know how the pathogen’s structure and how they function
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LIFE AND CELLS *Estimated that there are 10-100 million species on the planet *Many live apart from each other and many live in some kind of relationship *One popular relationship is parasitism *Over 3 million of the species are parasites *Parasites are organisms that live on or in another organism and are totally dependent upon their host *Parasitism results in damage to the host, sometimes minor damage and sometimes major damage that results in the death of the host *Estimates that the roundworm Ascaris is present in over a billion humans *Average human comprises 100 trillion cells, one hundred million million separate units of living matter *Of those 100 trillion cells only 10% or 10 trillion are human
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PROCESSES OF LIFE All of these living cells share four things in common: 1) They all grow and increase in size 2) They all reproduce, increase in number 3) They all respond to stimuli in their environment, many move in response to these stimuli, called taxis 4) They all metabolize: they take up nutrients from outside of themselves, use the nutrients sometimes changing them in chemical reactions, and use the resultant energy and newly formed chemicals to grow and reproduce
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EUKARYOTES VS PROKARYOTES *Eukaryotes have a membrane surrounding their DNA, a nucleus *Eukaryotes have several other organelles that are surrounded by a membrane *These organelles have different functions *Prokaryotes lack all of the above *In general, eukaryotes are larger and more complex than prokaryotes
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GLYCOCALYX Extruded from the inside > out, composed of polysaccharides, polypeptides, polyalcohols, or amino sugars . Loose, water soluble, called a slime layer. They come in two types: capsules and slime layers. Capsules are closely associated with the cells and do not wash off easily, and are composed of organized repeating units of one of the organic chemicals. Slime layers are more diffuse and are easily washed away. FUNCTIONS: 1) Enables bacteria to attach to surfaces. When sucrose is present Streptococcus mutans produces slime which forms a surface that allows other bacteria to aggregate on tooth surfaces, the result is dental plaque. Vibrio chlorae produces a glycocalyx that enables it to attach to the villi in the intestines of the host organism. 2) Protects the bacteria from the bodies phagocytes, defensive mechanisms. Encapsulated bacteria often cause disease whilst those that do not have capsules are inocuous.
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GLYCOCALYX Strains of Streptococcus pneumonia which have capsules often cause pneumonia, those w/o capsules do not. 3) Protects the cell from drying. Capsules and slime layers are
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Ch3_Structure and Function - CELL STRUCTURE AND FUNCTION...

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