PET 3322 Exam 1 Study Guide The Plasma Membrane The fluid mosaic model Membrane lipids o Lipid bilayer forms the fabric of the membrane o Composed of phospholipids molecules Polar head that is hydrophilic Uncharged nonpolar tail that is made of two fatty acid chains is hydrophobic Membrane Proteins o Integral proteins firmly inserted into the lipid bilayer Some may protrude from one membrane face only Most are transmembrane that span the entire width of the membrane and protrude on both sides Most are involved with transport Some may cluster together to form channels or pores through which water soluble molecules or ions can move through Others are carriers that bind to a substance and then move it through membrane Receptors o Peripheral proteins are not embedded in the lipid They attach loosely to integral proteins o Functions Transport from one side to other Enzymatic activity Substrate to produce products Receptors for signal transduction Neurotransmitters Hormones Membrane Transport o Passive process concentration gradient Will occur o Lipid soluble o Small enough o Assisted by carrier molecule Diffusion tendency of molecules or ions to move from high to low along their Simple diffusion unassisted diffusion of a lipid soluble or very small particle o Nonpolar and lipid soluble substances o O2 and CO2 o Dependent on the concentration gradient Facilitated diffusion o Limited by the number of protein channels available o Amino acids ions and glucose o Either travel by Carriers o Active Process Active Transport Binding to protein carriers in the membrane and ferried across Channels Osmosis the diffusion of a solvent such as water through a selectively Moves through water filled protein channels permeable membrane o Solutes attract water o Occurs when the concentration of a solvent is different on opposite sides of a membrane o Osmolarity total concentration of a solute in a solution Tonicity the cytosol o Isotonic solutions with same solute concentrations as that of o Hypertonic solutions having grater solute concentration than o Hypotonic solutions having lesser solute concentration than that of the cytosol All shriveled up loses water that of a cytosol About to burst gains water Carrier mediated facilitated diffusion Requires carrier protein that combine specifically and reversibly with the transported substance Solute pumps move solutes most ions against concentration gradient ATP is needed Distinguished according to their source of energy Primary Active transport o Requires carrier protiens o Energy to do work comes directly from hydrolysis of ATP o IE Sodium Potassium Pump Carrier is called Na K ATPase K inside the cell is 10x higher than outside and vice versa for Na Secondary Active Transport o Transport driven indirectly by energy stored in ionic gradients created by operation of primary active transport pumps o Move more than one substance at a time o Symport If the 2 transported substances are moved in the same direction o Antiport Is the transported substances wave to each other as they cross in opposite directions Vesicular Transport Transport of large particle and macromolecules across plasma membranes Exocytosis move substances from the cell interior to the extracellular space Endocytosis enables large particles and macromolecules to enter the cell o Phagocytosis cell engulfs some relatively large or solid material Epithelium Primary Functions o Protection o Absorption o Filtration o Excretion o Secretion o Sensory reception Special Characteristics o Polarity Apical surface an upper free surface exposed to the body exterior or the cavity of an internal organ Most have microvilli fingerlike extensions of the plasma membrane Basal surface lower surface attached to the apical Apical basal polarity cell regions near the apical surface differ from cells of the basal surface in both structure and function Tight junctions help keep proteins in the apical region of the plasma membrane from diffusing into the basal region and thus help to maintain epithelial polarity o Specialized contacts o Supported by connective tissue Basement membrane o Avascular Contains no blood vessel Epithelial cells are nourished by substances diffusing blood vessels in the underlying connective tissue o High regeneration capacity o Lumen Apical Surface Epithelial Basal Surface Basement Membrane Connective Tissue Blood Vessels Classification o Number of cell layers Simple epithelia consist of one layer Found where absorption secretion and filtration occur and thin is desirable Stratified composed of 2 or more Found where protection is important o Shape of cells Squamous cells flattened Easiest to pass through Cuboidal cells box like Columnar cells tall and column shaped Hardest most difficult to pass through o Simple Squamous Single layer of flattened cells Functions diffusion and filtration Present in kidney glomeruli lining of heart blood vessels lymphatic vessels o Simple cuboidal Single layer of cube like cells Function in hormone secretion o Stratified squamous Thick membrane composed of several layers of cell Function in protection of underlying areas subjected to abrasion Glandular Epithelia o Gland consists of one or more cells that make and secrete a particular product This product called a secretion is an aqueous water based fluid that usually contains proteins Classified as endocrine internally secreting or exocrine externally secreting depending on where they release their product and as unicellular or multicellular Connective Tissue Found everywhere in the body most abundant and widely distributed of the primary tissues Four main classes of connective tissue o Connective tissue proper includes fat and the fibrous tissue of ligaments o Cartilage o Bone o Blood Major functions o Binding and support o Protection o Insulation o Transportation blood Structural Elements o Ground Substance fibers Unstructured material that fills the space between the cells and contains the Holds large amounts of fluid and functions as a molecular sieve or medium through which nutrients and other dissolved substances can diffuse between the blood capillaries and the cells Provide support Collagen fibers strongest and most abundant Elastic fibers long thin fibers that form branching networks in the extracellular matrix Elastin allows them to stretch and recoil like rubberbands Reticular fibers short fine collagenous fibers with slightly different chemistry and form o Fibers o Cells Continuous with collagen
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