TRANSPORT MEMBRAN

SUPARMI, S.Si, M.SiBAGIAN BIOLOGI FAKULTAS KEDOKTERAN UNISSULAKuliah Transport melalui membran

Pendahuluan Transport Melalui Membran2Exocytosis, Endocytosis & Transcytosisd

F5-1Membran Sel

Bagian terluar selMembatasi bagian dalam dan lingk luarSebagai reseptor (penerima) rangsang dari luar seperti hormon dan bahan kimia lain, baik dari lingk luar maupun dari dalamMelindungi isi sel agar tidak keluarMengontrol zat yang keluar dan masukSebagai tempat terjadinya kegiatan biokimia (seperti reaksi oksidasi dan respirasi)

Fungsi Membran Sel

Struktur Membran Sel

Struktur Membran SelFosfolipid HYDROPHILIC heads (water liking) -Attracted to the water called POLAR

HYDROPHOBIC tails (water fearing) -Not attracted to the watercalled NON-POLAR

Struktur Membran SelEffect of temperature on the packing of the hydrocarbons Low temperatures the bilayer is in a gel state and tightly packed. At higher (body) temperatures the bilayer actually "melts' and the interior is fluid allowing the lipid molecules to move around, rotate, exchange places. This also allows movement of other components of the membrane.

Struktur Membran SelStruktur Membran SelCholesterol Another type of lipid in the membrane is cholesterol. The amount of cholesterol may vary with the type of membrane. Plasma membranes have nearly one cholesterol per phospholipid molecule. Other membranes (like those around bacteria) have no cholesterol.

Struktur Membran SelFungsi Cholesterol They immobilize the first few hydrocarbon groups of the phospholipid molecules. This makes the lipid bilayer less deformable and decreases its permeability to small water-soluble molecules. Without cholesterol (such as in a bacterium) a cell would need a cell wall.Cholesterol prevents crystallization of hydrocarbons and phase shifts in the membrane.

Struktur Membran SelGlikolipid 1.protective 2.insulators3.sites of receptor binding.

Two major types of membrane proteins Look at the picture and notice the integral proteins and the peripheral proteins. Struktur Membran SelPROTEIN

Transmembrane or embedded proteins allowing for passage through the membranes hydrophobic regionStruktur Membran SelINTEGRAL PROTEIN PERIFERAL PROTEIN Appendages to the membrane or may be found attached to integral proteins

Transport proteins

Usually integral Specific for soluteSome hydrolyze ATPStruktur Membran Sel

Sifat Membran Sel+ dapat dilewati- Tidak dapat dilewati

LALU LINTAS MATERIKELUAR MASUK SELPrinsipa. Ada pergerakan materi keluar masuksel.b. Nutrisi harus masuk.c. Sampah harus keluar.d. Ion bergerak keluar masuk.

2. Mekanismea. Transpor pasif- DifusiPergerakan partikel/molekul/ion terlarut dari tempat yang konsentrasinya tinggi ke tempat yang konsentrasinya lebih rendah.- OsmosisPergerakan cairan pelarut melalui membran semipermeabel dari tempat yang konsentrasinya lebih rendah, ke tempat yang konsentrasinya lebih tinggi.b. Transpor aktifPergerakan molekul/ion melawan gradien konsentrasinya dengan menggunakan energi yang dihasilkan sel itu sendiri.Mis : Pompa NatriumPompa CalsiumEndo/EksositosisLALU LINTAS MATERI KELUAR MASUK SEL

Cell membraneInside cellOutside cellTRANSPORT PASIFDIFUSI

Cell membraneInside cellOutside celldiffusionTRANSPORT PASIFDIFUSI

Cell membraneInside cellOutside cellEQUILIBRIUMTRANSPORT PASIFDIFUSI

Oxygen Non-polar so diffuses very quickly.

Carbon dioxide Polar but very small so diffuses quickly.

Water Polar but also very small so diffuses quickly.TRANSPORT PASIFZat-zat yang berdifusi

Gradien konsentrasi zatTemperature. Luas area permukaan/ ukuran molekulTipe molekul atau ion yang berdifusiTRANSPORT PASIFFaktor-faktor yang mempengaruhi kecepatan difusi

Large polar molecules such as glucose and amino acids, cannot diffuse across the phospholipid bilayer. Also ions such as Na+ or Cl- cannot pass.

These molecules pass through protein channels instead. Diffusion through these channels is called FACILITATED DIFFUSION.

Movement of molecules is still PASSIVE just like ordinary diffusion, the only difference is, the molecules go through a protein channel instead of passing between the phospholipids.TRANSPORT PASIFDifusi terfasilitasi

TRANSPORT PASIFDifusi Terfasilitasi

Cell membraneInside cellOutside cellProtein channelTRANSPORT PASIFDifusi Terfasilitasi

Cell membraneInside cellOutside cellProtein channeldiffusionTRANSPORT PASIFDifusi Terfasilitasi

Cell membraneInside cellOutside cellProtein channeldiffusionEQUILIBRIUMTRANSPORT PASIFDifusi Terfasilitasi

The cells of organisms are surrounded by and filled with fluids that are made mostly of water.The movement of (diffusion) of water through cell membranes is so important to life processes that it has been given a special name- OSMOSISTRANSPORT PASIFOsmosis

Osmosis : gerakan air dari potensial air lebih tinggi ke potensial air lebih rendah melewati membran selektif permeabel sampai dicapai keseimbangan dinamisTRANSPORT PASIFOsmosis

Cell membrane partially permeable.Inside cellOutside cellVERY High conc. of water molecules. High water potential.VERY Low conc. of water molecules. High water potential.Sugar moleculeDILUTE SOLUTIONCONCENTRATED SOLUTIONTRANSPORT PASIFOsmosis

Cell membrane partially permeable.Inside cellOutside cellHigh conc. of water molecules. High water potential.Low conc. of water molecules. High water potential.OSMOSISTRANSPORT PASIFOsmosis

Cell membrane partially permeable.Inside cellOutside cellOSMOSISEQUILIBRIUM. Equal water concentration on each side. Equal water potential has been reached. There is no net movement of waterTRANSPORT PASIFOsmosis

Osmosis important to cellular functions.RBC (red blood cells) are swimming in plasma which is mostly water with salts, sugars, and other nutrients.TRANSPORT PASIFThe cell & Osmosis

What is effect of immersing an animal cell in a hypertonic or hypotonic solution?

TRANSPORT PASIFEffect of Water on RBC

Isotonic solutions with the same solute concentration as that of the cytosolHypertonic solutions having greater solute concentration than that of the cytosol; water leaves the cell causing crenation (shrinkage)Hypotonic solutions having lesser solute concentration than that of the cytosol; water enters the cell causing swelling and potential lysisTRANSPORT PASIFEffect of Water on RBCTonicity how a solutions osmolarity affects cell volume

Types of Active TransportPrimary active transport: hydrolysis of ATP phosphorylates the transport protein causing conformational changeSecondary active transport: use of an exchange pump (such as the Na+-K+ pump) indirectly to drive the transport of other solutesSymport system two substances move across a membrane in the same direction (also called cotransport)Antiport system two substances move across a membrane in opposite directions (also called countertransport)

TRANSPORT AKTIFTIPE

Active Transport requires a cell uses energy to move molecules across the membrane.

Active TransportActive transport - movement of materials AGAINST the concentration gradient from low concentration to high concentration

Requires the cell to use energy (ATP)2 kinds:1. membrane pumps2. vesicle transports

Active TransportActive transport proteins:Move substrates against concentration gradientRequire energy, such as ATP Ion pumps move ions (Na+, K+, Ca+, Mg2+) Na+-K+ Exchange Pump moves both of these ions at the same time, each in the opposite direction (called antiport or countertransport)Proton Pump uses photosynthesis or food energy to create a proton concentration gradient that then is used to manufacture ATP

Sodium-Potassium Exchange Pump Active transport, carrier mediated: 1 ATP moves 3 Na+ out 2 K+ in This creates an electrical potential across the membrane Called the Transmembrane Potential

Transmembrane PotentialVoltage across a membraneResting membrane potential the point where K+ potential is balanced by the membrane potentialRanges from 20 to 200 mVResults from Na+ and K+ concentration gradients across the membraneDifferential permeability of the plasma membrane to Na+ and K+Steady state potential is maintained by active transport of ions

Expends metabolic energy to pump protons across membranesProton Pump (in Mitochondrial Membranes)Proton PumpPLAY

Vesicular TransportAlso called bulk transportTransport of large particles and macromolecules across plasma membranesDirectional Descriptive TermsExocytosis moves substance from the cell interior to the extracellular spaceEndocytosis enables large particles and macromolecules to enter the cell Receptor-mediatedPinocytosisPhagocytosisFunctional Descriptive TermsTranscytosis moving substances into, across, and then out of a cellVesicular trafficking moving substances from one area in the cell to anotherPhagocytosis pseudopods engulf solids and bring them into the cells interior

Receptor-Mediated EndocytosisReceptors (glycoproteins called clathrin) bind target molecules (ligands)Coated vesicle (endosome) carries ligands and receptors into the cell

Pinocytosis (cell drinking) Endosomes drink extracellular fluid

Phagocytosis (cell eating)pseudopodia (psuedo = false, podia = feet) engulf large objects in phagosomes

Getting the Big Stuff In and OutExocytosisIs the reverse of endocytosis

Summary

Semarang, 15NOVEMBER 2010

*The body is in a state of electrical disequilibrium because active transport of ions across the cell membrane creates an electrical gradient. Although the body is electrically neutral, cells have excess negative ions on the inside and their matching positive ions are found on the outside.

**Transporter protein mmebentang (melintang) membran mungkin memberikan suatu saluran hidrofilik melintasi membran yang bersifat selektif untuk zat terlarut tertentu. Aktifitas enzimatik protein yang berada dalam membran mungkin berupa enzim dengan sisi aktifnya dipaparkan ke zat-zat pada larutan disebelahnya. Dalam beberapa kasus, sejumlah enzim dalam membran sel disusun untuk melaksanakan jalur metabolisme.Transduksi sinyal protein membran memiliki tempat pengikatan dalam bentuk yang spesifik dengan meseesnger kimiawi, seperti hormon, Messeenger atau sinyal eksternal menyebabkan perubahan konformasi protein membran dan melepaskan pesan kedalam selPengenalan sel glikoprotein berfungsi sebagai label identifikasi yang secara khusus dikenali oleh sel-sel lainPenggabungan interselluler protein membran dari sel-sel bersebelahan mungkin dikaitakna bersama-sama dalam bentuk junctions.Pelekatan ke skeleton dan matrik ECM mikrofilamen atau komponen ECM lain terikat ke protein membran memepertahankan bentuk sel san menetapkan lokasi protein membran tertentu. Protein yang melekatakan pada ECM tertentu dapat mengkoordinasikan dengan perubahan ekstraselluler dan intraselluler. *Catra pengambilan kolestrol dari aliran darah ke sel-selEksositosislisosom primermembentuk Selective permeability restricts materials based on:SizeElectrical chargeMolecular shapeLipid solubility

*Osmosis isotoniscontoh..infus0,9%,sama dengan keomponen darah sehingga tidak terjadi krenasi ato mengkerutEmiositosis/eksositosisEndositosi

*Glukosaaa ndakair air*Masuk kedalam selDistance the particle has to moveMolecule size: Smaller is fasterTemperature: More heat, faster motionGradient size: The difference between high and low concentrationElectrical forces: Opposites attract, like charges repel

*Prinsip : mencapai homeostasis*Difusi tersi terpafsiltasi..Simport antiport*Volume sa*Hipotonik: NaCl.. 0,3 %..Hiper diatas 0,9%*Plasma is normally isotonic to cytoplasm of RBC. Cell is in dynamic equilibrium with plasma & maintains its shape.If RBC is placed in a hypertonic solution, solute concentration is greater in solution than inside the cell. Since RBC membrane is impermeable to solutes, water is driven to move. Thus, water tends to leave the cell to dilute the outside solute. The cell shrinks.If RBC is placed in a hypotonic solution, solute concentration is greater in cytoplasm of RBC. Here again, water is driven to move because the RBC membrane is impermeable to solutes. Thus, water tends to enter the cell. The cell swells & may even burst.

Note: Some single-celled protists (paramecium) live in fresh water. They use structures called contractile vacuoles to rid themselves of excess water that is continuously diffusing inward.****Contoh pompa ion H pada respirasi************