1 Notes 1 Human Physiology Tandy Homeostasis Cell Membrane and Cell Communication Total Body Water 2 3 intracellular 1 3 extracellular Intracellular Fluid 2 3 inside of the cells Extracellular Fluid 1 3 o Outside Cells 80 interstitial fluid between the cells o In Blood Vessels 20 plasma o Creates the internal environment within which our cells exist All physiological process that work together to maintain a relatively steady state in Homeostasis an organism Variables Body Temperature K Concentration pH Cell Membrane Made of phospholipid molecules that form a phospholipid bilayer Heads face outside of the bilayer and tails face inside of the bilayer when in water organized based on nature of the particles In the Cell Membrane o The bilayer o Proteins Phospholipid Head Phospholipid Tail Charged phosphate Hydrophilic water loving Polar Carbon tails Lipophilic lipid loving Non polar Minimally charged Integral Membrane Proteins integrated or embedded within the membrane Trans membrane protein all across the phospholipid bilayer Peripheral Membrane Protein on inside or outside of cell membrane not integrated Junctions between Cells 3 types 1 Desmosomes o Hold cells firmly together and provides mechanical strength o Resist forces that act to pull cells apart o Where body needs them to be ex skin o If damaged tissue that is not anchored i e tissue without desmosomes will slough off because nothing holding the cells tightly together and resisting the force trying to pull them apart o Localized and water cannot get around the desmosomes 1 Notes 2 2 Gap Junctions 3 Tight Junctions o Provides direct pathway for communications between cells o Important in rapid transmission of electrical signals o Restrict movement of large hydrophilic molecules between cells and regulating movement of molecules Need integral membrane protein trans membrane protein which is specific to that molecule so that only molecules with channels can get into cells o Extends around the entire cell o Polarize the epithelium cells adjacent to each other creating a boundary of cells Give the epithelium an apical surface surface facing the lumen top hollow portion and a basolateral surface surface facing the rest of the cells bottom and side the stuff o Present on absorptive surfaces because the molecules need to get into the cells and you want to only make sure you get what you need so you have specific channels etc Movement of Uncharged Molecules Passive Transport o No external energy necessary o Always occurs down a chemical gradient area of high area of low o Via Fick s Law the Rate of Flux movement across a membrane is related to concentration Membrane permeability Affected by lipid solubility size and shape of molecules temperature membrane thickness Increased net flux with small lipophilic molecules because membrane more permeable to those molecules Decreased net flux with large hydrophilic molecules because membrane less permeable to those molecules Surface Area of the membrane Increased net flux if membrane thin or has greater surface area Decreased net flux if membrane thick or has smaller surface area Concentration Gradient across the membrane Net flux is directly related to concentration gradient o Increase concentration gradient increase net flux more will come into out of a cell if the concentration gradient is steeper o Seeks to establish no net flux movement across the membrane but the movement is equal and opposite o 2 types of Passive Movement 1 Notes 3 1 Simple Diffusion Lipophilic molecules can diffuse directly across the cell membrane needs no help Small hydrophilic ions can move through channels and into the cell without interaction between channels and ions 2 Mediated Facilitated Transport Diffusion Hydrophilic molecules that are too large to go through a channel may be transported using a carrier molecule mediator carrier Transporter will change conformation spontaneously and the molecule binds to the facilitator and is transported Still move based on concentration gradient Use of a mediator based on o Specificity Binding sites have specificity for which molecules they can bind to Ligand molecule that will bind to a binding site Can be affected by minor alteration in the structure of the ligand or binding site o Saturation Ligands can only bind as long as there are binding sites available The availability levels off without regard to Based on the binding sites not the concentration concentration of the ligand o Affinity Ability of binding site to hold onto the molecules High if opposite charges and tight fit More able to transport because higher affinity and stronger bond If there is a high affinity outside cell and low affinity inside cell and binding site releases molecule Increasing the affinity of a carrier s binding site will increase the rate of transfer If it is an enzyme a more rapid reaction will result Ligands with similar chemical structures could compete for the same binding site and the one with the greater concentration and higher affinity will likely win o Competition Active Transport o Sibstances moved against their concentration gradient 1 Notes 4 o Primary Active Transport Directly uses ATP as energy source Ex Na K Pump Na and K moved against their concentration gradient with hydrolysis of ATP o 3 Na out 2 K in Always moves against concentration gradient o Secondary Active Transport Utilizes energy released from one ion typically Na moving down its concentration gradient to power the movement of a second substance across the cell membrane against its gradient Na always moves passively into the cell releases energy which gives the secondary transporter the energy to actively transfer the other molecule against its concentration gradient Cotransport if other substance is transported in same direction Countertransport if other substance is transported in opposite direction Movement of Water Moves passively down its concentration gradient Osmosis movement of water against a selectably permeable membrane caused by differences in solute concentration If pure water no net movement of water because no concentration gradient but if you add solute you make concentration gradient and water moves from area of high to low concentration gradient Types of Solutes o Penetrating distributes equally on either side of the membrane because it has the ability to cross the membrane and there is no concentration gradient and there is no effect of the movement of water because no concentration gradient