Biology_Chapter_6_Reading

Biology_Chapter_6_Reading - Biology Chapter 6 Reading...

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Biology Chapter 6 Reading MICROSCOPY Light Microscopes - visible light is passed through the specimen and then through glass lenses Electron microscope - focuses a beam of electrons through the specimen onto its surface - Scanning electron microscope (SEM) - detailing surface - Transmission electron microscope (TEM)- internal structure -But electron microscopes require the specimen cell to be dead COMPARING PROKARYOTIC AND EUKARYOTIC CELLS All Cells have - Plasma Membrane - cytosol - semifluid substance within the memebrane carrying the organelles -All cells have chromosomes carrying their DNA -All cells have ribosomes -Prokaryotic Cell - has DNA in nucleoid that has no membrane seperating it from the rest of the cell - Eukaryotic Cell - has a true nucleus bounded by nuclear envelope - Cytoplasm - the entire region between the nucleus and plasma membrane -Contains membrane bound organelles, absent in prokaryotic cells- Eukaryotic cells are bigger than prokaryotic -Mycoplasmas- smallest prokaryotic -Size limit imposed by the amount of DNA required to program metabolism and enough enzymes and other cellular equipment to carry out the activities necessary -Another cell size limit imposed by surface are to volume ration -**Smaller cell has greater surface area compared to volume -Surface area for exchange between cell and environment -Membranes can participate directly in the cell’s metabolism because many enzymes are built right into the membranes **Membrane provides different environment so incompatible processes can occur simultaneously NUCLEUS:GENETIC LIBRARY OF THE CELL -contains most of the genes in the eukaryotic cell - nuclear envelope - encloses the nucleus from the cytoplasm -Double membrane -Has 2 bilayerrs connected by nuclear pores -Inner and outer membranes are continuous at the pores pore complex - protein at each pore and regulates the entry and exit of molecules nuclear lamina - in the nuclear side of the enevelope, netlike array of protein filaments that maintains the shape of nucleus by mechanically supporting the nuclear enevelope
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chromosomes - DNA organized within the nucleus Each Chromosome is made up of Chromatin - complex of proteins and DNA -nucleolus - mass of densely stained granules and fibers adjoining part of the chromatin -Site for the synthesis of Ribosomal RNA (rRNA) -Assemble Ribosomal subunits with proteins imported from cytoplasm -Nucleus make mRNA, transported to the cytoplasm via nuclear pores and make proteins via ribosomes RIBOSOMES ribosomes - particles made up for ribosomal RNA and protein -CElls that have high rates of protein synthesis have high ribosome count Free Ribosomes - suspended in the cytosol bound ribosomes - are attached to the outside of the endoplasmic reticulum or nuclear envelope **Most of the proteins made on free ribosomes function within the cytosol **Bound ribosomes make progeins that are destined for insertion into membranes, for packaging within certain organelles or for export -Protein secretion cells have high proportion of bound ribosomes ENDOMEMBRANE SYSTEM
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