Human Physiology 4. Movement of Molecules PDF

Human Physiology 4. Movement of molecules 4. Movement of molecules 4.1 Contents...

Human Physiology 4. Movement of molecules 4. Movement of molecules 4.1 Contents MCQ Diffusion Through a membrane Through ion channels ↳FR Q Facilitate diffusion 12 nism a mean Active transport about Osmosis and tonicity Endocytosis and exocytosis 4.2 Diffusion or The movement of molecules from one location to another as a result of their random thermal motion. Flux _ _ _ _ : the amount of material crossing a surface per unit time. _ _ _Flux _Net _ _ _ _ : difference between fluxes in each direction. Diffusion equilibrium: _ _ _Flux _ _Net _ _ _ _= O ___ __ I " & ↑ - & ↑ ↑ - I Diffusion rate depends on: ↑ S - &... ↑ - ! ↑ ↑ - _ _ _ _ of particle Mass & & - - S ↑ - - & - I... ↑ Temperature S - ↑ ↑......, S Type of medium - L - - ↑ & & - Surface S & & Concentration Big net flux from L-R Net Flux = O & equilibrium Time for diffusion equilibrium - proportional to the square of the distance. ~ _10 _ _ for cellular size scale. _ _ms ~ _1_ _year _ _ _ for distances between organs. Ta = Du 4.3 Diffusion through a membrane time for ↳ longer Distance = longer reach Flux (J) through membrane: Diffusion to Difference in _Concentration _ _ _ _ _ _ _ _ _ _ _ _ _ (C) at each side equilibrium Surface _area _ _ _ (A) this Is of _ _ _ _ _ _ _ _ _ _ _ _ coefficient (P) combines permeability flow our or _ _ _ _ _ _ _(i) J = _PA((o - _____ ⑦ J-value means Inside outside - > solider? ↑ (onc from goes , outside - conc inside) 1 flow is ⑦ J-vale means hypon hyper inside > - outsiche  Human Physiology 4. Movement of molecules Flux across cell membranes I phosphateI ratty acid ; _1000 _ _,_000 _ _ _ _1, 000 _ _ _ _to _ _ _ _ _ _ times slower than through a water layer. Interior of phospholipid bilayer is _nonpolar ________: _Hydrophobic _ _ _ _ _ _ _ _ _ _ substances move through easily. om - Ex: oxygen, carbon dioxide, fatty acids, steroid hormones. _Hydrophilic _ _ _ _ _ _ _ _ _ _ materials do not diffuse readily through the membranes. particles charge not be substances Ex: ions and polar molecules. Q will ga t membrane Acid a game nonpolar casily go though & Fatty ⑦ able can bilayer aut d Phospholipid , ! ↓ D'Ad nonpar · Add 8 L channel in con - 4.4 Diffusion through ion channels ⑦ Channel: _Protein _ _ _ _ _ _ that spans the lipid bilayer. Single chain or _multimeric _ _ _ _ _ _ _ _ _ with subunits. specific Ions like Na+, K+, Cl-, Ca++ use _ _ _ _ _ _ _ _ protein channels to diffuse into and out of cells. Specificity determined by _ electric _ _ _ of the pore and its _ _ Size _ _ _ _ _ _ _charge _______ ↳ electrochemical Flux depends on _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ gradient - Concentration _ _ _ _ _ _ _ _ _ _ across the membrane. Membrane _ _ _ _ _ _ _ _ _ (_charge _ _ _ _ _ difference). B- B A * B- A - B - 5-A B B7- B B A - A O A - - A 2 A B- - A A B i B  Human Physiology 4. Movement of molecules 4.5 Regulation of ion channels Ion channels are _proteins _ _ _ _ _ _ _ _ _ _ _(shapes) _ _ _ _ _ _ _. They can change _conformation _ Channel _gating _ _ _ _ _ : opening and closing of ion channels. - Figure 4.1. Ion flow through an ion channel. Notice that it allows for a continuous flow. Types of gated channels: bird site Ligand _ _ _ _ _ _ -gated: respond to binding of chemical messenger. Ligandprotein it' Allosteric or covalent modulation. _Voltage _ _ _ _ _ _ -gated: respond to change in membrane potential. tocruatio _Mechanil _ _ _ _ _ _ _is _ _ _ _ -gated: respond to deformation of the membrane. open channels mechanical stress to ave 4.6 Mediated-transport systems and polar Molecules that are _ _ _ _large too _ _ _ _ _ for channels (ex: glucose, amino acids) are transported one-by-one or in small numbers across the membrane. Transporters are similar to ion channels: They are _ _transmembrane _ _ _ _ _ _ _ _ _ _ _ proteins. _ _ _ _ _ _ _ _(Transport They have chemical _ specificity ___ I dype of particle) But: Ion channels open and create a continuousflow _ _ _ _ (like bridge) = fast! Transporters change _shape _ _ _ _ at each transport (like ferry boat) = slower. inside the protein ↳ one side opens to allow particle enters ;However, > - the other side is closed when particle end does when shooting particle 3 the other open inside Human Physiology 4. Movement of molecules nosed open - - I open closed Figure 4.2. Solute transport by protein transporter. Notice that each transport event requires a back and forth change in conformation. -10 saturate easy Mediated-transport rate very _ factors: 3 E transporters Degree of _saturation _ _ _ _ _ _ _ _ _ of transporters. Each transporter has a maximum speed. Time it takes to complete each transport (speed of conformational change). Number of transporters on the membrane. cone & of particle are factors that determine speed of diffusion - through transporter 4.7 Facilitated diffusion Like simple diffusion, but employs transporter (mediated-transport system): Does not require _ATP ___ Tend to equal concentrations each side. Ex: _glucose ______ Converted instantly to _ _glucose-o-prosphate _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ when it enters the cell. This maintains a continuous _influ _ _ _ X_ _. Glucose (mitomodria) turn's into glose-6-phosphate in order to keep bringing in more guess into the cell 4  Human Physiology 4. Movement of molecules 4.8 Active transport Like facilitated diffusion but it uses _ _ _ _ _ _ to move molecules _against ______ a energy concentration gradient. Dumps Transmembrane proteins called “_ _ _ _ _ ”. Use one of two energy sources: ATP - _Primary _ _ _ _ _ _ active transport. electrochemical An _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ gradient across a membrane - secondary - active transport. & - 4.9 Primary active-transporters Enzyme _ATPase _ _ _ _ _ breaks down ATP, but ATP phosphorylates ATPase in _covalent _ _ _ _ _ _ _ modulation. ATPase changes snape _ _ _ _ _ and transports solute against concentration gradient. out transported outsidal 2kt): t + >more Na inside) - (less + k - ↓ in Po inside) ADD Nat t (less inside & · K (more PO ⑧ Major transporters transported in + _Nat/k + _ _ _ _ _ ATPase 2 K Found in every cell. Establishes and maintains the membrane potential. + + Ca _ _ _ _ ATPase of Keeps Ca2+ low in the cytosol. * Transportation _Ht _ ATPase & 2K + stomach changes acidity Nat in out - 3 in Maintains cytosol pH. gradient HYk + conc. _ _ _ _ _ ATPase is against Secrets acid in the stomach for digestion. ↳ O - more Intracellular= 5 more I ↳ Extracelluk =  Human Physiology 4. Movement of molecules EC 4.10 Secondary active transport - one molecules goes along EG while other goes against Ion transported _along _ _ _ _ electrochemical gradient. solutes more Another molecule (ex: glucose or amino acid) is cotransported & against _ _ _ _ _ _ _ _ its concentration gradient. high > - low Two binding sites: one for ion and another for cotransported molecule. there are outside Transport goesoprite (a) Ti) ter Since at will + coun wat Na more cell , along particle 2nd al main of inside direction - gradient * move conc at t Na its transport - CO - Y in goes (x) Y - 2nd particle as direction (na") same the main particle X against Paclick y even u go T note pointuse sell : cone : The what of of transport out in love Transport is _Active _ _ _ _ _ : based on electrochemical gradient (formed by pumps). At rest _10-40 _ _ _% _ _ of the ATP produced in the body is used by pumps to maintain the electrochemical gradient. _ Cotransport _ _ _ _ _ _ _ _ _ _ _ _ (symporter) moves molecules in the same direction. _ _ _ _ _ _ _ _ _ _ (antiporter) move molecules in opposite directions. _ _ _ _ _ _transport _ _counter 6 Human Physiology 4. Movement of molecules 4.11 Main membrane transport proteins Figure 4.3. Main transport proteins separated by type of transport mechanism. 4.12 Water polar Phospholipid bilayer does not allow water to pass through because water is _ _____ Transmembrane protein channels called _ _Aquaporins _ _ _ _ _ _ _ _ allow water through. Aquaporin _expression _ _ _ _ _ _ _ _ _ on the membrane varies among cells. Especially important in the kidneys. 7  Human Physiology 4. Movement of molecules 4.13 Osmolarity - water : Hyper ↑ A net flux of water across the membrane is called _Osmosis ______. - Total Osmolarity = _ _ _ _ _ _ particle concentrations. Hypo Not the same as molarity! 1 osmol = 1 mol of _particle Total ________. But salts produce 2 or more particles (cations and anions) when they ionize. 1 mol of CaCl2 in 1l of water = 3 solute 1 Cat 2 Cl _ osmol solution. 3 particles = particle , Normal intracellular osmolarity 300 _ _ _ mOsm. Relative to the cell, the surrounding solution can be hyperosmotic, to H20 hypoosmotic or isosmotic. Permeable and impermeable - L to solute low High conc conc. e Figure 4.4. Demonstration of osmosis. Water flows against gravity to aleviate the osmotic pressure across the membrane. 8  Human Physiology 4. Movement of molecules 4.14 Tonicity -determing water flow > - T Solutions classified by their effect on cells: __Isotonic _ _ _ _ _ _ : cells maintain volume. _ _Hypotonic _ _ _ _ _ _ _ : cells swell. only _ _Hypertonic _ _ _ _ _ _ _ _ : cells shrink. Only _ _Non-penetratory _ _ _ _ _ _ _ _ _ _ _ _ _ solutes matter solutes Figure 4.5. Cell tonicity. NP for tonicity. The others will not cause _ water _ _ _ _ to flow in or out. Can a solution be hyperosmotic and hypotonic? _ _ _ , if: The solution has a lot of _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _. The cell has more _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ solutes. 9 # Human Physiology 4.15 Endocytosis 4. Movement of molecules It is the transport of molecules that cannot cross the plasmatic membrane. Membrane folds and forms _ _ _ _ _ _ _ containing fluid. Figure 4.6. Three types of endocytosis. 4.16 Exocytosis Movement of molecules out of the cell via vesicles. Functions: _ _ _ _ _ _ _ _ _ plasmatic membrane removed by endocytosis. _ _ _ _ _ _ new components (proteins) to the membrane. _ _ _ _ _ _ _ _ _ membrane-impermeable molecules (ex: protein hormones). Secretion of vesicles is usually triggered by an increase of _ _ _ _ in the cytosol. Figure 4.7. Exocytosis. 10 Human Physiology 4. Movement of molecules 4.17 Epithelial transport Epithelial cells form a _ _ _ _ _ _ _ between the organism and the outside world. Their cells are _ _ _ _ _ _ _ by materials entering and leaving the body. _ _ _ _ _ _ sheets of cells separate the internal tissues from tubes. Ex: intestines, kidneys _ _ _ _ _ _ _ _ _ _ _ _ pathway Diffusion between adjacent cells is very _ _ _ _ _ _ _ because of tight junctions. How limited varies across epithelia. _ _ _ _ _ _ _ _ _ _ _ _ _ pathway Enter cell, cross the cytosol, and exit across opposite membrane. Diffusion or mediated transport _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ membranes differ in ion channels and transporters. 11