THE CELLULAR LEVELOF ORGANIZATIONAnatomy & Physiology IClinton Hackney
Key TermsCell -structural and functional unit of all known livingorganisms. It is the smallest unit of an organism that isclassified as living.EukaryoticProkaryoticCell Doctrine:The cell is the basic unit of life,New cells come from pre-existing cells,The cell is the fundamental unit of structure, physiology, andorganization.Cell Division –All cells arise from pre-existing cells viacell division.MitosisMeiosis
Introduction to the CellThe cell is generally divided into three main components:Plasma membraneCytoplasmNucleusPlasma Membrane –The cells flexible outer surface that acts as aselective physical barrier.Separates the cells internalenvironment from its external environment.Cytoplasm –All the cellular contents between the plasmamembrane and the nucleus (to include organelles).Cytosol –The fluid portion of the cytoplasm that contains water, dissolvedsolutes, etc.This is where signal transduction and some metabolism occur.Organelles –Membrane bound structures suspended in the cytosol thatcompose the major metabolic machinery of the cell.Nucleus –A large, double membrane bound, organelle that housesthe DNA of the eukaryotic cell.DNA is wound intochromosomes.Chromatin FiberChromatidsUnit of chromosomes that encode proteins are calledgenes.Nucleolus –Portion of Nucleus where ribosomes are produced.
The Plasma MembraneA flexible and sturdy barrier thatsurrounds and contains the cytoplasm ofa cell.Described using thefluid mosaic model.
The Plasma MembraneA flexible and sturdy barrier that surrounds and contains thecytoplasm of a cell.Described using thefluid mosaic model.Membrane lipid molecules exchange places 10 million times per second(Completely around the cell in 2 minutes).The lipid bilayer –The structural framework of the plasmamembrane.Consists of two back-to-back layers made up ofthree types of molecules:PhospholipidsCholesterol(increases membrane rigidity)GlycolipidsNote:The bilayer arrangement occurs because the lipids areamphipathicmolecules (meaning they have polar andnonpolar parts.