Cell Membrane: Water Transport, Ion Diffusion - Science Lecture Notes PDF

Movement Of Substances Across Cell Membranes  Selective permeability allows for separation and exchange of materials across the plasma membrane h to low Shig move across membranes by...

Movement Of Substances Across Cell Membranes  Selective permeability allows for separation and exchange of materials across the plasma membrane h to low Shig move across membranes by energy  Substances _______________ diffusion and ____________ active ________________ transport polar or charged cannot go thro plasma men - larged glucose ; Nat - channel small hydrophob can go plasma men be tall doesn't stop - nonpolar , Four basic mechanisms by which solute molecules move across membranes  -high energy to low energy Diffusion packed then diffuse out - elevator ex) to chaos least energetic State universe ; go , The Diffusion of Water Through Membranes  Diffusion of water through a ↑ rate oppo semipermeable membrane is called osmosis. top ,  Cells swell in hypotonic solution  Cells shrink in _________________ hypetonic cousin solutions and ↑ smalinnt more solute outside hypercell , water wantso out  Cells remain unchanged in isotonic solutions. ↑ in d water out nice rate The effects of differences in the concentration of solutes on opposite sides of the plasma membrane The Diffusion of Water Through Membranes in plants : hypotonic solution. be have cell wall , being hypo allows cell to push against the wall. No proggie  Diffusion of water through a semipermeable membrane is called osmosis.  Cells swell in hypotonic solution  Cells shrink in _________________ solutions and  Cells remain unchanged in isotonic solutions. The Diffusion of Water Through Membranes in Plants plantcoWagnewater lets  Plants utilize osmosis↓in different ways as they are usually _________________ hypotonic compared to their fluid environment.  There is a tendency for water to enter the cell.  In hypertonic solutions the plant cell undergoes plasmolysis. plant cell loses Moeshrink - men helps W controlling canc. plasma maintain environ insided out plant in gen. Plant help , The effects of osmosis on a plant cell  dead anything is in eq have to ion balance cells maintain The diffusion of ions through membranes X  Cells maintain an imbalance of ions across the ofplasmain membrane more each remember wher there is to Extracellular Intracellular Ionic gradient # concentration concentration Na+ 150 mM 10 mM 15x K+ 5 mM 140 mM 28x Cl– 120 mM 10 mM 12x Ca2+ 10–3 M 10–7 M 10,000x H+ 10–7.4 10–7.2 Nearly 2x (pH of 7.4) (pH of 7.2) Ion Concentrations Inside and Outside a Typical Mammalian Cell state bcNa high 100 wheng got in will do to grad low en out in anything get cone The diffusion of ions through membranes: simple diffusion through leak channels Some cells have channels that are constitutively (always) _____________. Open Ions flow down their concentration gradient (high to low) a These channels are sometimes called leak always I channels. ALL channels, including leak channels, are specific for the ions they can transport & Size ex) sodium lear , only charge transfer sodium. Ipased on pore , carry The diffusion of ions through membranes: gated channels open Most ion channels can exist in either an not continuously if open or a closed conformation, and are called gated. The three major categories of gated channels are: came decin x change 1. _______________-gated Voltage channels: Conformational state depends on the difference in ionic charge on the two sides of the membrane. bind to opens depends on ligand so ~ 2. ________________-gated Ligand channels: Conformational state depends on the binding of a specific molecule (ligand). Stir closed til pressure Someone push against · 3. Mechano-gated channels: - Conformational state depends on mechanical forces that are applied to the membrane. The Diffusion of Ions through Membranes likeectue a X All channels are very specific in the ions they transport because they have special structures that can only fit ions of certain charges and atomic size.  What's an example of voltage gate Unique properties of 5 in to change respons charge channels: the voltage- gated potassium (K+) Channeladopta channel poschargestageenate bunch ↳  Once opened, more than 10 million K+ ions can pass through per second. (when open goes out  After the channel is open for a few milliseconds, the movement of K+ ions is “automatically” stopped.  Can exist in three different states: open, mate no inactivated, and closed. now volarge, words - diffroball yell detect Her can in - Y change change voltage - sodium out Kinside voltage Conformational states of a voltage-gated K+ ion channel erest respond voltage change inactivated can doesn't to , respond change  large to in channel allows mole go Facilitated Diffusion t  In many cases, the diffusing substance binds selectively to a membrane-spanning protein, called a facilitative transporter. like enzyme Increas acts in cell  Facilitated transporters can mediate the movement of solutes in both directions.  _________________ facilitated _____________ diffusion is similar to an enzyme-catalyzed reaction. to in cell wo this , takes longer for glucose get Schematic model of facilitated diffusion  Facilitated Diffusion: Human perspective  Insulin plays a key role in maintaining proper blood sugar levels.  An increase in blood glucose levels triggers the secretion of insulin, which stimulates the uptake of glucose. Einsul eats lose  Rising insulin levels stimulates the movement of transporters to the cell surface. - matemans to allow glucose to more faster trans Kinetics of facilitated diffusion compared to simple diffusion  gradient generates maintains unequal ion balance ↓ ATP Active transport needs w energy , > - ↑ moves against conc gradient  Cells maintain an imbalance of ions across the plasma membrane, which cannot occur by either simple or facilitated diffusion.  Gradients are generated by active transport.  Coupled energy input is needed like ATP hydrolysis, absorbance of light, electron transport, or the flow of other substances down their gradients. Extracellular Intracellular Ionic gradient concentration concentration Na+ 150 mM 10 mM 15x K+ 5 mM 140 mM 28x Cl– 120 mM 10 mM 12x Ca2+ 10–3 M 10–7 M 10,000x H+ 10–7.4 10–7.2 Nearly 2x (pH of 7.4) (pH of 7.2) Ion Concentrations Inside and Outside a Typical Mammalian Cell  Primary Active Transport: Coupling Transport to ATP Hydrolysis Na atwas Pricedus wants to in , go zachted d ejects Sodiumagains · in fits in sodiu pump. - open when 3 bind, ATP goes in 3bind change cont ATPcloud -Scarries Zions protein in ? Sodium high  The Na+/K+ ATPase (sodium-potassium pump)  The ratio of Na+:K+ pumped is 3:2. -phosphorylation needs phosphate from ATP  The ATPase is a P-type pump, in which phosphorylation causes changes in conformation and ion affinity that allow transport against gradients. Defects in Ion Channels and Transporters as a Cause of Inherited Disease  Several inherited disorders have been linked to mutations in genes encoding ion proteins channels.  Cystic fibrosis (CF) is a genetic disease I characterized by abnormal fluid secretions from tissues and caused by a defective chloride channel. abnormal fluid genetic disease by - defect in chloride channels C = out chloride ot. Ho wants in water rushes out of cell bact cangow Nat out by No ATPase water out of cell keeping most Effects on lung function from the absence of the CFTR protein The Human Perspective Defects in Ion Channels and Transporters as a Cause of Inherited Disease Inherited disorder Type of channel Gene Clinical consequences Familial hemiplegic migraine (FHM) Ca2+ CACNL1A4 Migraine headaches Episodic ataxia type-2 (EA-2) Ca2+ CACNL1A4 Ataxia (lack of balance and coordination) Hypokalemic periodic paralysis Ca2+ CACNL1A3 Periodic myotonia (muscle stiffness) and paralysis Episodic ataxia type-1 K+ KCNA1 Ataxia Benign familial neonatal convulsions K+ KCNQ2 Epileptic convulsions Nonsyndromic dominant deafness K+ KCNQ4 Deafness Long QT syndrome K+ HERG, KCNQ1, or Dizziness and sudden death from ventricular Na+ SCN5A fibrillation Hyperkalemic periodic paralysis Na+ SCN4A Periodic myotonia and paralysis Liddle syndrome Na+ B-ENaC Hypertension (high blood pressure) Myasthenia gravis Na+ nAChR Muscle weakness Dent’s disease Cl– CLCN5 Kidney stones Myotonia congenita Cl– CLC-1 Periodic myotonia Bartter’s syndrome type IV Cl– CLC-Kb Kidney dysfunction and deafness Cystic fibrosis Cl– CFTR Lung congestion and infections Cardiac arrhythmias Na+ Many different genes Irregular or rapid heartbeat K+ Ca2+ Co-Transport: Coupling Transport to Existing Ion Gradients  Potential energy stored in ionic gradients is GLUTI transport utilized to perform work,. channel. in uses Na grad  Na+ concentration is kept low by a Na+/K+- to trans glocose. ATPase pump. active glu Na yes goes Na in agh energy to go in  Diffusion of sodium ions down a concentration gradient drives the cotransport of glucose. to to also piggy brek wants rushin glucose - Sodium go in -gen ! Wa in low by ATP pmup. Secondary transporter: the Na+ gradient helps to transport glucose by a Na+/glucose co-transporter Co-Transport: Coupling Transport to Existing Ion Gradients a uses everytof ions tha in Y  Secondary active transport gas of glucose is an example of grad symport. ar z doing at same time one If Nat in , other mole out. Use of cone grad eng  Antiporters or exchangers ↳ oppway move two transported species in opposite directions.  During the transport cycle, the protein’s binding sites gain alternating access to the cytoplasm. Secondary transporter: the Na+ gradient helps to transport leucine into bacteria  neurons work imbalance ions when charge potential dif Membrane Potentials - separated and Nerve Impulses  Potential differences exist when charges are separated. electrici brain electical cells of uses ~  Neurons are specialized cells for information transmission using changes in membrane potentials.  _____________________ dendrites receive incoming information; the cell body contains the nucleus and metabolic center of the cell; the __________________ is a long extension Laxoqhteaara for conducting outgoing impulses. (top) The structure of a nerve cell; (bottom) A composite micrograph of one rat hippocampal neuron  -maintained by sodium potassium pup The resting potential - imbalance of ions Extracellular Intracellular Ionic gradient concentration concentration Na+ 150 mM 10 mM 15x K+ 5 mM 140 mM 28x Ion Concentrations Inside and Outside a Typical Mammalian Cell inside cell-slightly than out weg The Resting Potential  The _______________ resting _______________ potential is the membrane potential of a nerve or muscle cell “at rest”. ↑  K+ gradients maintained by equal # & out the Na+/K+-ATPase are inside responsible for the resting inside = lower hey potential. I Cell -connect electode volt measure , if out in polarized solution , voltage is I I & rest imbalance in I votage. -electrode meagues axon , get my more neg outside tellsv inside slightly neg than to create electrical / make sig , depolarize well - ionic imbal , neron advanty conc closer to outside to transmit Signal stimulated chan. open als , I towards out go Measuring a membrane’s resting potential The Action Potential  When cells are stimulated, Na+ channels open, causing membrane_______________________. depolarizatio  When cells are stimulated, voltage-gated - Na+ channels open, triggering the action potential. Nat open channel axon all activated When voltage gate , ~  Excitable membranes exhibit all-or-none behavior. Formation of an action potential  -ecieve signal signal 1. Initiation phase axon receive - change voltage open man charge signal , change channel open lets open  all Nat channels open be so much depoltzing sodim in cell Cause 2. Rising phase volage. change gre ↓ to volage open breadschange a grshn new change - in + vol change  3. Peak of depolarization all + of(H) going Na detet, voltage state switch to Inactive no matter how hardv try will not open open , No Na & peak going it  v-channel inactive. Natalpase still course Nat penpot 3. Re-polarization -every It in so bak to get rest  4. Hyperpolarization - gave inactivatingchannel open , closed. > Martin = polent - rest closed Closed senses ↳Na 5. Return to resting potential acts diren by Voltage channels gated a all openinmi We to drive Kpolent ↓ hyperpora belowrest a gas e & out causing beweg. it No to Not in lose tal no pat in to eventually close, No atpage bring bat donor Propagation of Action Potentials as an Impulse when one channel on axon opens all open , allow none. ,  APs produce local membrane currents depolarizing adjacent membrane regions.  Once triggered, a succession of action potentials passes down the entire length of the neuron without any loss of intensity. Propagation of an impulse results from the local flow of ions unidirectionally Electrical Signaling in Plants  Plants contain voltage-gated potassium channels.  Plants and animals have similar abilities to use membrane potentials.  Membrane potential is used for long range signaling. Venus fly trap action potential Think, Pair, Share Question 3 How does a potassium channel allow potassium ions to flow within it but prevents sodium ions from flowing within it?