Cells.doc - Cells I. Cell Structure and Function A. Cell...

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CellsI. Cell Structure and FunctionA. Cell Theory1. A cell is the basic structural and functional unit of living organisms2. All cells come from pre-existing cells3. The activity of an organism depends on both the individual and the collectiveactivities of its cellsA) Principle of Complementarity – the biochemical activities of cells are dictatedby their specific subcellular structures4. Most cells are capable of self-reproductionB. Typical cells are made of three main parts:1. Cell (plasma) membrane2. Nucleus3. Cytoplasm and cytoplasmic organellesC. Cell Membrane1. A flexible, selectively permeable membrane that defines the extent of a cell byseparating intracellular fluid (ICF) from the extracellular fluid (ECF)2. The Fluid Mosaic Model – 1972A) Composed of a phospholipid bilayer1) Hydrophilic heads face outward2) Hydrophobic tails face inwarda) creates a hydrophobic corethat gives the membrane selectivepermeability3) Two layers are moveable (fluid)B) The plasma membrane contains many embedded structures1) Proteins:a) Transmembrane proteins – proteins that typically extend all the wayacross the membrane and play a role in many functionsi) Transport proteins(a) Channels, pores, carriers, and pumpsii) Enzymesiii) Receptorsiv) Intercellular junctionsv) Cell-cell recognitionb) Surface (peripheral) proteins – proteins that are attached to either side ofthe membrane and are mostly involved with:i) Acting as enzymes & receptorsii) Attaching to the cytoskeleton for movement and supportiii) Aid in changing the shape of the cell2) Cholesterol & Steroids – lipid structures that help to stabilize the membranea) Necessary due to the lack of a cell wall
3. Associated StructuresA) Microvilli (“little shaggy hairs”) – finger-like projections that increase thesurface area of the plasma membraneB) Membrane junctions1) Tight junctions – membrane proteins fuse the two adjacent cell membranestogethera) Prevent the movement of substances between cells2) Desmosomes – anchoring junctions that are associated with protein filamentsa) Provide strength3) Gap junctions – membrane proteins form channels between adjacent cellsa) Allow impulse transmission between cellsD. Nucleus1. The nucleus is the control center of the cell that also contains DNA in the form ofchromatin/chromosomes

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Term
Spring
Professor
N/A
Tags
Physiology, Anatomy, Cell Cycle, Cell Theory, Mitosis, Sister chromatids, c Cell Membrane

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