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oct 23 compartmentalization

oct 23 compartmentalization - L iv in g c e lls a r e s u r...

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1 Living cells are surrounded by a plasma membrane . This cellular membrane is continuous, and separates the cell’s internal chemistry from the often inhospi- table environment outside. Plasma membrane BACTERIUM ANIMAL CELL Purves, Fig. 4.4 & 4.7 Plasma membrane In some cells (e.g. plants; bacteria, fungi), the plasma membrane is supported externally by a second barrier called the cell wall . Eukaryotic cells ( left ) differ from prokaryotic cells ( above ) in that the inside of the cell is highly compartmentalized into discrete structures called organelles . ANIMAL CELL Compartmentalization is brought about by internal cell membranes that are not continuous with the plasma membrane. Compartmentalization is one of the hallmarks of eukaryote cells, especially specialized cells. What are some potential advantages of compartmentalization? Cytoplasm - general term for that portion of the cell situated between the nuclear envelope and the plasma membrane: Cytosol is the aqueous fluid part of the cytoplasm. It contains many dissolved ions and other small molecules. Cytoskeleton is an array of fibrous proteins that permeate the cytosol. They give the cell structural support, and are important for cell movement (more on Wednesday). Organelles are large, discrete cytoplasmic structures. Some ( e.g. mitochondria) are surrounded by their own cell membranes; other ( e.g. ribosomes) float in the cytosol. cytoskeletal protein fibers compare to Purves, Fig. 4.9 Nucleus • Houses the nuclear genome , i.e. chromo- somes that contain the majority of the cell’s DNA. • Site of nearly all gene transcription (DNA RNA).
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