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Human Physiology H3a
Handout 3 Membrane Dynamics
| Question | Answer |
|---|---|
| Anatomical Compartments | focus on anatomy; line a cavity; parietal, visceral |
| Functional Compartments | focus on physiology; cell membranes line a cavity |
| Cell Membranes/Plasma Membrane | Barrier btwn ICF and ECF; a structure that lines a cavity; a phospholipid bilayer that forms the outer boundry of an organelle or a cell; maintains electrical activity; difference in voltage inside and outside of the cell; neurons and muscles depend on it |
| functions of the cell membrane | selective permeability; permeable and impermeable molecules |
| Selective Permeability | Allows physical isolation of the environments; regulation of passage of materials into and out of the cell; role in physical support of cell itself |
| Permeable | Able to cross membrane (lipid bilayer) from ICF to ECF and vise versa; small things; usually lipophilic and hydrophobic |
| Lipophilic | Fat LOVING; can associate with lipids |
| Lipophobic | Fat HATING |
| Hydrophilic | Water LOVING |
| Hydrphobic | Water HATING |
| Immpermeable | Cannot pass; Large things esp.cannot pass; usually lipophobic and hydrophilic |
| What are cell membranes made of? | Lipid, Protein, Carbohydrate |
| Lipid | A barrier made mostly of phospholipid, sphingolipid and cholesterol |
| Protein | For activity and functionality; includes integral proteins, peripheral proteins (attached just inside or outside membrane) and lipid-anchored proteins |
| Carbohydrate | May be attached to the membrane |
| Membrane Functionality mostly provided by proteins | channels, carriers/transporters, docking-marker acceptors, membrane bound enzymes, receptors, cell adhesion molecules adn self recognition |
| Docking-marker acceptors | hold on to cytoplasm to support the cell |
| Receptor | Bind signal molecules released from other cells near or far |
| Cell adhesion molecules | holds in locations to other cells or within matrix |
| Membranes are the basis for the bodies functional compartments | Total Body fluid, ECF, ICF (40%), plasma (6%), ISF (15%); there is also solids (1/4) and fat (1/4) |
| Fluid compartments | Because we maintain homeostasis of these fluid in the ECF mainly |
| Plasma | Inside the capillary; Primarily measure plasma for homeostasis and it is what is primarily acted on |
| ISF | outside of the capillary; in tissues directly around the cells but not in blood volume |
| Capillary | The boundry btwn plasma and ECF |
| Membrane transport | The memb. perm. of any molecule/particle is determined by:relative solubility of the particle in lipids and the size of the particle; important because its where cells exchange material with the environment to survive and get rid of what they don't need |
| Size | Larger size = less permeability Smaller size = increase permeability |
| Force is require to drive MOVEMENT of PERMEABLE particles | passive forces and active forces |
| Passive force | DOESN't require addt'l E (ATP) to function |
| Active force | DOES require E (ATP) |
| Passive Transport | is DIFFUSION |
| Diffusion | only uses the energy of MOLECULAR MOTION of molecules; is passive rocess, H to L; for CO2, o water and alcohol; diffusion ends at equilibrium |
| Diffusion is faster: | With higher conc. differences, over SHORT distances, at HIGHER TEMPS, and for SMALLER molecules |
| H to L concentration | in a single direction for that particular molecule TO equilibrium; the influence of that individual concentration independently |
| Continues to equilibrium | Equal concentration of ICF and ECF of the cell making it no longer a H to L concentration gradient-just equal |
| Impacts on rate of diffusion | increase conc. gradient = increase diffusion rate; short distance = increase in diffusion rate; thicker membrane = decrease in diffusion rate |
| Dynamic disequilibrium | OSMOTIC EQUILIBRIUM, CHEMICAL AND ELECTRICAL DIS EQUILIBRIUM Between ICF ands ECF; Homeostasis doesn't necessarily mean equal in ICF |
| Exception of being maintained at a diseuilibrium | WATER; Osmotic equilibrium; water is freely moveable and will move TOWARDS equilibrium |
| Why Disequilibrium? | Na and Cl are high outside the cell and low inside, K is low outside the cell and high inside the cell |
| Na and CL | are like the ocean = salty ECF; can't use Na to explains equilibrium b/c charged particles (na, cl, k, ca) ar eNOT lipid soluble s0 ZERO perm. thru cell membrane therefore need a protein chnl or carrier |
| Protein and large anions (negative ions) | low inside the cell and ZERO outside the cell |
| Diffusion across a membrane | RD depends on the permeability of the membrane for a particular substance, DR is directly prop. to SA; DR is inversly prop to Mem. thickness and Ficks law |
| Membrane thickness | RD decreases when MT increases; INVERSE |
| Surface Area | RD increases when SA increases; DIRECT |
| Ficks Law of diffusion | increase in rate of diffusion = increase in SA, increase in lipid solubility and increase in molecular size; DECREASE in RD with an increase in MT |
| Water | The body is mostly water; we have less water as we age; more water mols in ECF tha Na so water can change the vol of the cell; women have less than men |
| Osmosis | Mvmnt of water; The diffusion of water through a semipermeable membrane down its concentration gradient; great significance for maintaining life down its conc. grad. H to L; NOT A SOLN-ONLY WATER |
| How can osmosis be measured? | Osmotic Pressure |
| NaCl | Saline solution = .9% soln describes conc. of SOLUTE |
| For WATER, focus on the solute | Ex. 2 solns A. 5% solute B. 10% solute A has more water, B has more solute INCREASE solute = DECREASE water |
| If soln A and B are combined... | Solute moves from H to L untilit reaches equilibrium; NO CHANGE IN VOL |
| If only permeable to water... | Water will move from A to B b/c will move from H to L until equilibrium so volume WILL change; A vol will go down which creates a vol change also creating OSMOTIC PRESSURE |
| Osmolarity | is given a measure of solute conc.-given in terms of the # fo particles (Osm = osmoles/liter); osmolarity communicates the solute conc in a soln (the number os particles in a soln); doesn't provide about type of particle only # of |
| Normal osmolarity of ICF | is approx. 300 and DOES NOT CHANGE; ECF can change because of sweating etc. |
| 2 solns may be... | isosmotic, hyperosmotic or hyposmotic to eachother; LOOKING FOR CHANGES IN THE ECF; if ICF and ECF are not equal then teh cel shrinks or swells which they dislike |
| isosmotic | same # of particles as ICF; 300 mOsm |
| hyperosmotic | soln with more particles = less water; Cell SHRINKS; LESS than 300 mOsm |
| hyposmotic | soln with less particles = more water; Cell SWELLS; MORE than 300 mOsm |
| How does osmolarity of a soln affect the body? | if soln is hyposmotic to ICF, water will move into cells and SWELL |
| if soln is isosmotic or hyperosmotic the water will... | depends on whether the solutes in the soln are PENETRATING or NONPENETRATING |
| Tonicity DOES describe how a soln will affect cell vol | The TYPE of particle is important for determining the effect on cell volume |
| Penetrating | CAN move; LESS water in soln |
| Nonpenetrating | CAN NOT move; MORE water in soln |
| Crenation | Cells SHRINKING |
| Haemolysis | Cells SWELL and burst |
| Tonicity | Soln in respect to the cell |
| What determines tonicity? | BOTH the NUMBER OF PARTICLES in the soln and the TYPE OF PARTICLE in the soln |
| What is the tonicity of hyposmotic solns? | ALWAYS HYPOTONIC; fewer particles in soln compared to cell-cell swells |
| What is the tonicity of isosmotic or hyperosmotic solns? | Need to know # of NonPen particles; 3 Rules |
| Rule 1 | if # of NP particle is equal = isosmotic, so is isotonic soln |
| Rule 2 | if NP particles are: MORE than 300 = hypertonic = shrinks |
| Rule 3 | if NP particles are LESS than 300 = hypotonic = swells |
| .9 saline is isosmotic. Tonicity? | isotonic |
| dextrose is isosmotic. Tonicity? | hypotonic |
| dextrose and .9 saline is hyperosmotic. Tonicity? | isotonic b/c cell shrinks H to L until eqilibrium-isotonic |
| .45 saline is hyposmotic. Tonicity? | always hypotonic |
| dextrose and .45 saline is hyperosmotic. Tonicity? | hypotonic |
| Assisted Membrane Transport | most things are NP so dont diffuse so we need to assist mvmnt. 2 main mechanisms for selective transport of mols across the Cell Mem: CARRIER-MEDIATED TRANSPORT AND VESICULAR TRANSPORT |
| Carrier-Mediated Transport | mvmnt of mols across a cell mem w/ a transmembrane protein; 2 types of proteins:chnl proteins and carrier proteins |
| Vesicular transport | capture larger things in vescicles and pull in or spit out in a membrane blood vesicle |
| endocytosis | pull in |
| exocytosis | spit out |
| channel proteins | form an open pore that penetrates the membrane;open to both sides; high rate of transport; hole; protein pens thru; very selective only to Na, Cl or K; one at a time; most are gated; may close or open and can control that |
| carrier proteins | only open to one side at a time; outside or inside;uniport carriers and cotransporters slower rate of transport; glucose, amino acids |
| Channel Proteins are either... | Nongated (leak) channels or gated channels |
| Nongated channels/leak channels | ALWAYS OPEN; fewer in # |
| Gated channels | more of them; diff selection fro diff neurons and named by the gate; Mechanically gated chnls, ligund/chemically gated chnls an voltage gated chnls |
| Mechanically gated channels | change shape to open gate Ex. based on temp change |
| Chemically gated channel | binds to a gate and opens Ex. neurotransmitter |
| Voltage gated channel | Change in electrical nature inside (ICF) cell Ex. charged amino acids |
| Channels are named based on: | the molecule that passes through the channel and the type of gate |
| Properties of carrier-mediated transport | Specificity, Saturation and Competion; similar to enzymes |
| Specificity | ex. glucose may bind but galactose may not |
| Saturation | chnl binds as rapidly as possible |
| Competition | presence of two things slows down transfer |
| Uniport carrier proteins | carry a single substrate at a time; assists in mvmnt; H to L Ex. just glucose H to L down conc. gradient |
| Cotransporters | Symport carriers and antiport carriers |
| Symport carriers | moves two or more substrates in the SAME direction |
| Antiport carriers | move substrates in OPPOSITE directions |
| Facilitated diffusion is PASSIVE carrier mediated transport | protein mediated diffusion of lipophobic mols too large to fit thru a chnl; NO OUTSIDE E REQ'D; mols travel according to their CONC. GRAD, TOWARDS EQUILIBRIUM; fascilitated b/c sol is immpermeable |
| ACtive transport energy is DEPENDENT carrier mediated transport | transport of mols AGAINST their CONC. GRAD; PRIMARY ACTIVE TRANSPORT and SECONDARY ACTIVE TRANSPORT; consumes E b/c against its conc. grad |
| Primary active transport | directy using/comsuming ATP in the mvt of that ion (Na, K, H, Ca); most important in the Na/K pump (50% activity at rest is due to this pump |
| Secondary active transport | Using E that exists in the Na gradient (high outside/low inside) and use the force to transport something else b/c actions are depepndent on Primary AT; couple the donhill transport of Na w? the uphill trans. of another mol ex. duodenum |
| Active Transport: Na/K Pump | Open to the inside, has high affin. for Na, binds then consumes ATP and drives a change in shape of protein, opens to other side, Na is released at same time has high affin for K so opens to inside of cell and repeats cycle again nonstop |
| Na/K Pump cont. | pumps Na against conc. grad to outside of cell and does samt to k to maintain homeostasis of cell which is Na: high outsie, low inside and for K: high in, low out; For Na, ATP provides E to drive Na out and K, then Phosbinding to K causes shape to chng |
| Secondary Active transport of glucose in small intestine | No fasc. diff. b/c against conc. grad. to move into cell (no human has primary AT for glucose); Glucose and Na bind to symporter, Na drives glucose against its conc. grad and the pump removes Na and keeps Na conc low inside cell; needs ATP |
| Vesicular transport | phagosytosis,endocytosis and exocytosis |
| Phagocytosis | cell EATING = cell eating if cell is to large |
| Endocytosis | bring into cell;Pinocytosis and receptor mediated endocytosis; endocytosis and exocytosis are involved in every cell |
| Pinocytosis | form a vesicle to sample whats in the environment |
| Receptor mediated endocytosis | pull in membrane bound things b/c in need |
| Exocytosis | get out of the cell, controlled too |
| Transepithelial transport | from outside to inside the body ex. digestive tract; mols entering the body through an epithelium need to cross two membranes Apical and basal membrane; so NEED ALL3: Primary AT, Secondary AT and fascil. diff.; epithel cells are polarized; transcytosis |
| epithelial cells are polarized | apical surface transporters (primary AT), basolateral surface transporters use Na/K pump (secondary AT) |
| transcytosis | endocytosis mvmnt thru cell (from apical to basal) then exocytosis |
| fascilitated diffusion | high conc. of glucose in cell compared to low outside cell so can move glucose down its conc. grad via fascillitated diffusion |
| Resting Membrane Potential | there;s an electrical gradient across the cell mem of all living cells; membrane, potential, resting; all cells at rest have an electrical status inside their cells which is their RMP; (IS NEGATIVE) |
| Electrical gradient of RMP | -60 mV more negative outside of cell |
| Membrane | a seperation of opposite charges across the membrane; an insulation; charged particles stay seperate |
| Potential | Can be used to do work; seperated charges have the potential to do work (potential energy) |
| Resting | a 'Steady State'phenomenon |
| Electricity review | Human body is electricaly NEUTRAL; opposite charges attract eachother; identical charges repel; charges move through a conductor; charges are seperated by an insulator, electrical potential is measured in volts; voltage diff in cells is mV |
| The cell membrane and elctrochemical gradients | Add a chnl; allows a + charged ion to move out, inside is missing change so negative compared to outside; outside has extra charge |
| What determines the RMP? | 1. diff in ion conc inside or outside the cell Concentration diff = chemical force 2. Electrical Force, Concentration gradients maintained by pump 3. selective permeability of the cell 4. eqiibrium potentials for permeable ions |
| Chemical force | diff in conc. of ions on either side of the cell membrane Ex. if we open a Na cell, sodium rushes into the cell and carrrying its charge with it making the inside more +; if we open a K cell, K moves out so more - inside cell(selective permeability) |
| Electrical force | seperationof charges on either side of the membrane; Ex. open chnls to K, cell becomes - so negativity eventually attracts K back |
| Concentration gradient | ions responsible for RMP are Na, K and A (anions); concentration differences in Na and K are produced AND maintained by the Na/K pump; each turn of the pump removes a net +1 charge from ICF so it dorectly effects the RMP |
| Concentration diff in Na and K are PRODUCED AND MAINTAINED by the na/k pump | [Na] ECF = 150 mM, ICF = 15 mM [K] ECF = 5MM, ICF = 150 mM |
| Each turn of the pump removes a net +1 charge from ICF, it diectly contributes to the RMP | 2 K IN and 3 Na OUT so omet +1 charge w/ each turn of the pump |
Created by:
Lkellyfly
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