lecture 2- membrana, transport, compartimente lichidiene

Upload: vio-mincu

Post on 14-Apr-2018

224 views

Category:

Documents


0 download

TRANSCRIPT

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    1/43

    1.Cell1.Cell HomeostasisHomeostasis

    Body FluidBody Fluid CompartmentsCompartments

    1.11.1 CellCell MembraneMembrane

    ((structurestructure,, functionsfunctions ,, actionaction

    potentialpotential ))

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    2/43

    Human Body structure

    Cell

    tissue

    organ

    system

    HUMAN BODY

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    3/43

    Coordination of Systems and Organs

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    4/43

    Claude Bernard(1813-1878)

    La fixit du milieu intrieur est

    la condition de la vie libre.

    The fixity of the internal

    environment is the

    condition for free life.

    Homeostasis

    WalterCannon(1929)

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    5/43

    HOMEOSTASIS Cannon W.B., 1939

    -all mechanisms through which bodily equilibrium is

    maintained ( body fluid composition, temperature, blood pressure, blood

    glucose level)

    INTERNAL MILIEU Claude Bernard-,, all around ,, cells

    - offers nutritives substances

    - realises elimination of metabolites

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    6/43

    The cell : morpho functional unit of human body.

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    7/43

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    8/43

    Cell Membrane

    - separates / unites two compartments with different composition

    - intracellular space (compartment , environment)- extracellular space ( compartment )

    Na+

    K+

    Cl-

    Proteins

    Glucose

    Osmolarity

    extracelular

    142 mM/L

    4.4 mM/L102 mM/L

    7 g/dL

    5.5 mM/L

    291

    intracelular

    15 mM/L

    120 mM/L20 mM/L

    30 g/dL

    -

    290

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    9/43

    Cell membrane

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    10/43

    Transport

    Enzymatic activity

    Sending informations

    Intercellular comunications

    Intercellular recognition

    Attachment to cytoskeleton

    Functions of the cell membrane :

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    11/43

    Hystory :

    Overton (1895): if a substance is

    more lipo-soluble , it has a better

    permeability through the membrane- conclusions regarding the lipid

    profile of the cell membrane .

    Davson and Danielli (1935) they

    introduce the concept of a protein

    structure for the cell membrane .

    Singer & Nicholson (1972)- they

    offer the model of ,,fluid mosaic,,-

    phospholipids and cholesterol form

    a a fluid lipid bilayer where

    proteins can move free. In

    conclusion cell membrane is a

    dynamic structure with specificcharacteristics in order to

    accomplish various functions.

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    12/43

    The cell membrane is a lipid bilayer semipermeable structure

    allowing the passage only for some molecules .

    - no H2O, ions, hidrophyle molecules.

    - yes - gas, hidrophobe substances .

    Membrane proteines allow transport for H2O, ions and hidrophyle

    molecules .

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    13/43

    CELL MEMBRANE lipids

    proteins

    glucides

    MEMBRANE LIPIDS: -phospho-lipids

    -cholesterol

    -phospholipids - contain fat acids - C chain, (carboxil group terminal)

    - particular characteristics:

    - hidrophyle part ( C chain)

    - hidrophobe part ( carboxil group )

    - lipid bilayer

    - hidrophobe head (inside )

    - hidrophyle head (outside)

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    14/43

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    15/43

    MEMBRANE PROTEINS

    A. INTEGRAL PROTEINS

    - connected with hidrophobe layer of the

    membrane .

    1.transmembrane proteins: cross lipidic bilayer

    - channels:

    - pomps:

    - pores-receptors:

    2.proteins expressed only on one face of the membrane

    B. PERIPHERAL MEMBRANE PROTEINS

    - connected with hidrophyle part of the lipidic layer or with integral proteins- cytoskeleton - role in membrane rigidity

    - glicocalix -role n intercellular atachment

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    16/43

    MEMBRANE PROTEINS

    A. INTEGRAL PROTEINS - c o n nec te d w it h h id ro p ho b e la y er o f the m embrane .

    1.transm embra ne proteins: cross l ipidic bi layer - channels: allows the passage only for substances with small molecule with

    electric charge

    - gates acctive or innactive - selectivity

    - pomps: - pores -receptors:

    2.p ro t ei ns ex p r es se d o n ly o n o n e fa c e o f t he m e m b ra n e

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    17/43

    MEMBRANE PROTEINS

    A. INTEGRAL PROTEINS - c o n nec te d w it h h id ro p ho b e la y er o f t h e membrane .

    1.transm embra ne proteins: cross l ipidicbilayer

    - channels: - pomps: - pores - channels without gates , allways

    open.

    - ex. aquaporines ( allow thepassage for water renal colector tube)

    -receptors:

    2.p ro teins ex p res se d o nl y o n o n e fa c e of t he m e m b ra n e

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    18/43

    MEMBRANE PROTEINS

    A. INTEGRAL PROTEINS - connected with hidrophobe layer of the membrane .

    1.transmemb rane proteins: cross lipidic bilayer - channels: - pomps: allow ions transfer against concentrationgradient or voltage gradient. - pores: - receptors:

    2.proteins expressed on ly on one face of the membrane

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    19/43

    MEMBRANE PROTEINS

    A. INTEGRAL PROTEINS - c on n ecte d w ith h id ro pho be la y er o f t he m e m b ra n e .

    1.transm embrane proteins: cross lipidic bi layer - channels: - pomps: - pores

    -receptors:

    2.p ro t ei ns e x pr es se d o n ly o n o n e fa c e o f t h e m e m b ra n e

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    20/43

    MembraneMembrane ReceptorsReceptors

    areare proteinprotein moleculesmolecules thatthat reactreact withwith ligandsligands inducinginducing specialspecial reactionsreactions

    insideinside thethe cellscells.. TheThe mostmost importantimportant receptorsreceptors areare classifiedclassified asas adrenergicadrenergic andand

    cholinergiccholinergic

    1.1. AdrenergicAdrenergic receptorsreceptors are of 2are of 2 typestypes ALPHAALPHA andand BETABETA ..TheyThey reactreact toto

    sympatheticsympathetic neurotransmitterneurotransmitter-- norepinephrinenorepinephrine ..

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    21/43

    The actions of norepinephrine depend on the type of receptorsactivated :

    Alpha 1 receptors - contraction of smooth muscles in vessels andbronchioles

    Alpha 2 receptors - contraction of smooth muscles of digestive sphincters. Beta 1 receptors - excitatory effects on heart . Beta 2 receptors - relaxation of smooth muscle in bronchioles and

    muscular vessels.

    2. Cholinergic receptors are of 2 types nicotinic and muscarinic. Theyreact especially to acetylcholine

    NicotinicNicotinic receptorsreceptors areare stimulatedstimulated byby acetylcholineacetylcholine andand nicotine.nicotine. TheyTheyareare foundfound inin allall ganglionicganglionic synapsessynapses andand neuromuscularneuromuscularjunctionsjunctions wherewhereareare blockedblocked byby curaracurara..

    ..MuscarinicMuscarinic receptorsreceptors areare stimulatedstimulated byby acetylcholineacetylcholine andand muscarine.muscarine.TheyThey areare foundfound atat targettarget organsorgans whenwhen acetylcholineacetylcholine isis releasedreleased byby postpost--ganglionicganglionic neuronsneurons ((parasympatheticparasympathetic)).. TheyThey areare blockedblocked byby atropine.atropine.

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    22/43

    EnzimesEnzimes

    -- ProteinsProteins thatthat playplay

    importantimportant rolesroles ininproteinprotein synthesissynthesis

    insideinside thethe cellscells

    -- adenylateadenylate cyclasecyclase

    -- guanilateguanilate cyclasecyclase

    -- phospholipasephospholipase CC

    -- proteinprotein kinaseskinases A, CA, C

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    23/43

    SSecondecond MMessengersessengers -- substancessubstances insideinside thethe cellscells thatthat mediatemediate thetheactionaction ofofligandsligands actingacting onon thethe cellscells

    cAMPcAMP

    cGMPcGMP

    IP3IP3

    DiacylDiacyl--glicerolglicerol

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    24/43

    The skeleton maintains the shape of the cells ( during cell

    divisions), realises some selective movements or activities of

    intercellular transport ( vesicles )

    PERIPHERAL PROTEINS

    -CYTOSKELETON-

    PERIPHERAL PROTEINSPERIPHERAL PROTEINS

    --CYTOSKELETONCYTOSKELETON--

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    25/43

    CYTOSKELETONCCYTOSKELETONYTOSKELETON

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    26/43

    - Using as a criterium the dimensions of transported molecules:

    - microtransfer system

    - macrotransfer system

    1. Microtransfer system

    PASSIVE TRANSPORT- transport according the concentration gradients of

    substances

    - without energy consumer

    ACTIVE TRANSPORT

    -against gradients

    - with energy consumer

    Transport of substances across the cell membrane

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    27/43

    1. PASSIVE

    TRANSPORT

    1 .1.DIFFUSION :

    -3 types :

    - simple diffusion .

    - diffusion facilitated

    by carrier protein

    - diffusion using

    channel proteins

    1.2. OSMOSIS

    Transport of substances across the cell membrane

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    28/43

    1.1.1 .Simple Diffusion- without energy consumer- takes place until all concentrations are equal.

    -substance flow depends of :- concentrations difference ( D )

    -membrane permeability ( P ) Fick low : Flow D x P x S- surface ( S)

    - liposoluble substances cross the membrane dissolving in lipidic bilayer

    (O2, CO2)- Hidrosoluble substances cross membranes using membrane proteins (

    channels )

    1. PASSIVE TRANSPORT

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    29/43

    Simple Diffusion

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    30/43

    1.1.2. Diffusion facilitated by

    carrier protein

    - Selectivity

    - Specificity

    - Saturation

    - takes place according gradients .

    - with superior speed and debit than

    concentrations difference

    - uses a carrier protein

    - without energy consumer

    - stops when concentrations become equal.

    - limitated by a maximum capacity of transport

    imitat induced by the saturation of the

    transporter ( ex. glucose )- low transport capacity in comparation with ions

    channels (102-103 molecules/sec)

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    31/43

    1.1.3.Diffusion using channel

    proteins

    - for particles with electric charge.

    - takes place according gradients .

    - with superior speed and debit than

    concentrations difference

    without energy consumer

    - stops when concentrations become equal.

    Ions channels :

    - High selectivity for only one ion- With permeability modulation of the

    channel ( ex.- membrane potential )

    A

    B

    A = poarta activare

    (deschis de depolarizare)

    B = poarta inactivare

    (nchis de depolarizare)

    Na channel

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    32/43

    1.2. OSMOSIS-Mechanism of passive transport

    -Allows passage of water from a compartment with lower concentrations ina compartment with higher concentration

    Osmotic pressure - a force used to stop the movement of water through a

    membrane which separate a solution from pure water.

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    33/43

    2. ACTIVE TRANSPORT

    - against gradients- with energy consumer

    2. 1. PRIMARY ACTIVE TRANSPORT

    2.2. SECONDARY ACTIVE TRANSPORT

    Transport of substances across the cell membrane

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    34/43

    2. 1. PRIMARY ACTIVE TRANSPORT

    - uses a system directed coupled with an energy reactions .

    - ionic pumps

    - energy source = ATP ( synthesized by mithocondrion )

    - ATP -- ADP + P (ATP-ase)

    - ATP-ase Na/K or Na pump - in almost cell membranes. ( role in

    maintenance of high concentration of K inside the cell - maintenance of

    membrane potential )

    - inhibited by medicines - digitala, ouabaina

    2. ACTIVE TRANSPORT

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    35/43

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    36/43

    Ca2+

    H+

    Ca ATP-ase4 Muscle cell .4 Endoplasmic reticulum .

    H+ ATP- ase4 renal tubular cells acidification ofurine .

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    37/43

    2.2. SECONDARY ACTIVE TRANSPORT

    4 the primary active transport generate chemical gradients or electricalgradients which represent ,,forces used to transfer of other substancesusing a common transporter.

    4 simport co-transport ( glucose )4 antiport contra- transport ( Na-K )

    INT

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    38/43

    4CYTOSIS- Transport of big particles across cell

    membrane - 5-400 nm.- Specific for macromolecules:

    - proteins- lipoproteins

    - polizaharides

    Endocytosis vesicles are incorporatedin cells by invagination , using ATP.

    phagocytosis for solid particles- pinocytosis for liquid particles

    Exocytosis vesicles are eliminated from

    the membrane .

    Trancytosis - macromolecules cross cellmembrane .

    - macrotransfer system-

    Transport of substances across the cell membrane

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    39/43

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    40/43

    MEMBRANEMEMBRANEPOTENTIALPOTENTIAL

    -- BecauseBecause ofofthethe selectiveselective

    permeabilitypermeability ofofcellcell membrane,membrane,therethere isis aa differentiateddifferentiated repartitionrepartition

    ofof ionsions insideinside andand outsideoutside ofofthethe

    cellcell..

    -- InsideInside predominatepredominate potassiumpotassium

    ionsions,,whilewhile outsideoutside predominatepredominate

    sodiumsodium ionsions,, thethe interior ofinterior ofthethe

    cellcell beingbeing more negative asmore negative ascomparedcompared withwith thethe exterior.exterior.

    TheThe differencedifference ofof electricalelectrical chargescharges createscreates aa membranemembrane potentialpotential ofof--7070mVmV at rest (at rest (restinrestingg potentialpotential).).

    PotassiumPotassium ionsions havehave aa tendencytendency toto leakleak outout byby facilitatedfacilitated diffusiondiffusion throughthroughchannelchannel proteinsproteins.. MostMost ofofsodiumsodium channelschannels areare gatedgated andand remainedremainedclosedvclosedv keepingkeeping thethe concentrationconcentration outsideoutside highhigh..

    TheThe differencedifference isis maintainedmaintained byby thethe active transport ofactive transport ofionsions acrossacross thethemembranemembrane byby thethe sodiumsodium--potassiumpotassium pumppump ..

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    41/43

    WhenWhen thethe cellcell receivesreceives aasignal,signal, likelike aa voltagevoltagevariationvariation,,thethe permeabilitypermeability ofof

    thethe membranemembrane changeschangesbecausebecause voltagevoltage gatedgatedsodiumsodium channelschannels openopen andandsodiumsodium flowsflows inwardinward..

    TheThe insideinside ofofthethe cellcell brieflybrieflybecomesbecomes moremore positivepositive thanthanoutsideoutside..

    The abruptThe abrupt modificationmodification ofofthethe polaritypolarity,, withwith aadepolarisingdepolarising andand aarepolarisingrepolarising phasephase,,constitutesconstitutes thethe actionactionpotentialpotential..

    WhenWhen thethe depolarizationdepolarization isisendedended thethe sodiumsodium channelschannelscloseclose andand potassiumpotassium

    channelschannels open.open. FinallyFinally,, thethe sodiumsodium --

    potassiumpotassium pumppump becomesbecomesoperationaloperational andand restoresrestores thetherestingresting potentialpotential ..

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    42/43

    ActionAction PotentialPotential

  • 7/27/2019 LECTURE 2- Membrana, Transport, Compartimente Lichidiene

    43/43

    TheThe restingresting andand actionaction potentialspotentials cancan bebe measuredmeasured usingusing intracellularintracellularmicroelectrodesmicroelectrodes , made of, made ofthinthin glassglass tubestubes withwith aa sharpsharp tip,tip, filledfilled withwith

    potassiumpotassium chloridechloride..

    TheThe microelectrodesmicroelectrodes cancan bebe introducedintroduced inin thethe cellcell withoutwithout thethedestructiondestruction ofof thethe membranemembrane andand thethe differencedifference ofof electricalelectrical potentialpotentialisis recordedrecorded onon oscilloscopeoscilloscope..