BSCI 201: Anatomy & Physiology I Chapter 3 Notes- Part 2
BSCI 201: Anatomy & Physiology I Chapter 3 Notes- Part 2 BSCI201
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This 5 page Class Notes was uploaded by mehrnazighani Notetaker on Tuesday September 20, 2016. The Class Notes belongs to BSCI201 at University of Maryland - College Park taught by Justicia Opoku-Edusei in Fall 2016. Since its upload, it has received 40 views.
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Date Created: 09/20/16
Anatomy & Physiology Chapter 3 Notes- Part 2 by Mehrnaz Ighani . Osmosis: movement of solvent across a selectively permeable membrane (Fig. 3.7d) Water diffuses through plasma membranes: 1. Though the lipid bilayer 2. Through specific water channels called aquaporins (AQPs) . Osmolarity: measure of total concentration of solute particles . Water concentration varies with the number of solute particles because solute particles displace water molecules When solute concentration increases, water concentration decreases and vice versa . Water moves from low solute concentration (high water conc.) to high solute concentration (low water conc.) . Equilibrium: same concentration of solutes and water on both sides with equal volume on both sides When solutions of different osmolarity are separated by a membrane permeable to all molecules, both solutes and water cross membrane until equilibrium is reached. (Fig. 3.8a) When solutions of different osmolarity are separated by a membrane that’s permeable only to water, osmosis will occur (Fig. 3.8b) Same concentration of solutes and water on both sides with unequal volume . Movement of water causes pressures: 1. Hydrostatic pressure: pressure of water inside cell pushing on membrane 2. Osmotic pressure: tendency of water to move into cell by osmosis o High conc. of solutes in the cell leads to high osmotic pressure . Tonicity: ability of a solution to change the shape or tone of cells by altering the cells’ internal water volume (Fig. 3.9) 1. Isotonic solution: same osmolarity on both sides, volume remains unchanged . used to increase blood volume 2. Hypertonic solution: high osmolarity than inside of cell so water flows out of cell resulting in cell shrinking (crenation) . given to ed ematous (swollen) patients to pull water back into the blood 3. Hypotonic solution: low osmolarity than inside of cell so water flows into cell resulting in cell swelling which can lead to lysing (bursting) . given to patients who are experience dehydration such as diabetic ketoacidosis and hyperosmolar hyperglycemic state . Active processes: 1. Active transport 2. Vesicular transport . Both require ATP to move solutes across a plasma membrane because: 1. Solute is too large for channels 2. Solute is not lipid soluble 3. Solute is moving across its concentration gradient . Active transport: Requires carrier proteins (solute pumps) . Bind specifically and reversibly with substance being moved . Some carriers transport more than one substance: 1. Antiporters: one substance into cell while transporting one substance out of cell 2. Symporters: 2 different substances moved in the same direction Moves solutes against their concentration gradient (low to high) 2 types: 1. Primary active transport: requires energy directly from ATP hydrolysis 2. Secondary active transport: required energy is obtained indirectly form ionic gradients created by primary active transport o Primary active transport: (Fig. 3.1) . energy from the hydrolysis of ATP causes change in shape of transport protein . shape change causes solutes (ions) bound to protein to be pumped across membrane . Ex. of pumps: Ca, H (proton). Na-K pumps . Na-K pump is the an antiporter pump that pumps Na out of cell and K back into cell using the Na-K ATPase enzyme . Present in all plasma membranes especially active in nerve and muscle cells . Na and K move down their concentration gradient . Maintains electrochemical gradients which involve both concentration and electrical charge of ions o Secondary active transport: (Fig. 3.10) . depends on ion gradient that was created by primary active transport system Energy stored in gradients is used indirectly to drive transport of other solutes Low Na concentration is maintained inside of cell by Na-K pump which strengthens Na’s inward movement through diffusion Na can drag other molecules with it as it flows into cell through carrier proteins (usually symporters) in the membrane Some sugars, amino acids, and ions are transported into cell via secondary active transport . Vesicular transport: Involves transport of large particles, macromolecules, and fluids across membrane in membranous sacs called vesicles Requires ATP and includes endocytosis and exocytosis: 1. Endocytosis: transport into cell . 3 types of endocytosis: 1. Phagocytosis (cell eating) 2. Pinocytosis (cell drinking) 3. Cell-mediated endocytosis 2. Exocytosis: transport out of cell Transcytosis: transport into, across, and then out of cell Vesicular trafficking: transport from one area or organelle in cell to another Endocytosis: (Fig. 3.11) . involves formation of protein coated vesicles . it is a very selective process b/c substances being pulled in must be able to bind to its unique receptor . some pathogens are capable of hijacking receptors in order to enter the cell . once vesicle is pulled inside cell, it may: 1. Fuse with lysosome 2. Undergo transcytosis o Phagocytosis: . membrane projections called pseudopods form and flow around solid particles that are being engulfed . formed vesicle is called a phagosome . used by macrophages and WBCs . phagocytic cells move by amoeboid motion where cytoplasm flows into temporarily extensions that allow cell to creep (Fig. 3.12a) o Pinocytosis: (Fig. 3.12b) . plasma membrane enfolds, bringing extracellular fluid and dissolved solutes inside cell (fuses with endosome) . routine and nonselective . main way of nutrient absorption . membrane components are recycled back to the membrane o Cell-mediated endocytosis: (Fig. 3.12c) . involves endocytosis ns transcytosis of specific molecules . many cells have receptors embedded in clathrin-coated pits which will be internalized along with the specific molecule bound Ex. enzymes, LDLs, iron, and insulin . Toxins may be taken into a cell this way . Caveolae: similar pits and different protein coat from clathrin, but still capture s specific molecules and use transcytosis (Ex. folic acid) Exocytosis: (Fig. 3.13a) . material ejected from the cell . activated by cell surface signals or changes in membrane voltage . substances are ejected in enclosed secretory vesicles . Protein on vesicle called v-SNARE finds and hooks up to target t- SNARE proteins on the membrane . some subs. exocytosed: hormones, neurotransmitters, mucus, cellular waste . Resting membrane potential (RMP): Electrical potential energy produced by separation of oppositely charged particles across plasma membrane in all cells . difference in electrical charge between 2 points is called voltage Voltage occurs only at membrane surfaces . rest of cell and extracellular fluid are neutral . membrane voltages range from -50 to -100 mV (inside of cell is more – relative to outside of cell) . NOTE: potassium ion is the key player in RMP (Fig. 3.14) . K diffuses out of cell through K leakage channels down its conc. gradient . negatively charged proteins can’t leave as a result so cytoplasmic side of cell membrane becomes more negative . K is then pulled back by the more – interior b/c of its electrical gradient . when the drive for K to leave the cell is balanced by its drive to stay, RMP is established . most cells have an RMP around -90 mV . electrochemical gradient of K sets RMP . Na also affects RMP b/c Na is attracted to inside of the cell due to negative charge . if Na enters the cell. It can bring up RMP to -70 mV . membrane is more permeable to K than Na so K is the primary influence on RMP . Cl doesn’t influence RMP b/c its conc. and electrical gradients are balanced . RMP is maintained through action of the Na-K pump which ejects 3 Na out of the cell and brings 2 K back inside . rate of active pumping of Na out of the cell = the rate of Na diffusion into the cell And that’s how steady state is maintained . neuron and muscle cells upset this steady state RMP by intentionally opening gated Na and K channels . Cells interact with their environment by responding directly to other cells or indirectly to extracellular chemicals . Cell interactions always involve glycocalyx Cell adhesion molecules (CAMs) Plasma membrane receptors Works Cited Lindsey, Jerri K., Katja Hoehn, and Elaine Nicpon Marieb. Human Anatomy & Physiology, 9th Edition Elaine N. Marieb, Katja Hoehn. Boston, MA: Pearson, 2013. Print.
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