Egészségügy | Felsőoktatás » Dr. Zsembery Ákos - A sejtfiziológia alapjai, a sejtmembrán szerkezete és funkciói

A SEJTFIZIOLÓGIA ALAPJAI BASICS OF CELL PHYSIOLOGY A SEJTMEMBRÁN SZERKEZETE ÉS FUNKCIÓI THE STRUCTURE AND FUNCTIONS OF CELL MEMBRANES Dr. Zsembery Ákos Protoplazma Protoplasm • A sejtet felépítő anyagokat összefoglalóan protoplazmának nevezzük • Substances that make up the cell are collectively called protoplasm - víz water - ionok ions - fehérjék proteins - lipidek lipids - szénhidrátok carbohydrates HOL VANNAK MEMBRÁNOK A SEJTEKBEN? WHERE ARE MEMBRANES IN THE CELLS? Plasma membrane. Endoplasmic reticulum. Golgi apparatus. Nucleus. Mitochondria. Lysosomes. Az extracelluláris és az intracelluláris folyadék összetétele Compositions of extracellular and intracellular fluids Membrane Structure Current model: Fluid-Mosaic Model - The lipid bilayer is the core of the model which is present in fluid state. - Individual lipid molecules move laterally. LIPIDS + PROTEINS - Proteins penetrate the entire bilayer and exist as a mosaic. +

CARBOHYDRATES LIPIDS OF THE CELL MEMBRANE I. LIPIDS OF THE CELL MEMBRANE II. LIPIDS OF THE CELL MEMBRANE III. Lipid Asymmetry For many membranes, lipid composition of the two monolayers is different. This asymmetry is generated by phospholipid translocators & maintained because of difficulty of flip-flop. A lipid asszimetria funkcionálisan fontos Lipid Asymmetry is Functionally Important • A protein kináz C (PKC) aktiválásához szükséges, hogy kötődjön a membrán belső felszínén elhelyezkedő foszfatidilszerinhez. • Protein kinase C (PKC), an enzyme that initiates signaling by phosphorylating other proteins, is activated by binding to the cytosolic face of the plasma membrane • PKC requires negatively charged phosphatidylserine for its activity Lipidraftok a plazmamembránban Lipid Rafts in the Plasma Membrane Function: to accommodate and concentrate certain types of proteins to enable them to function together; e.g proteins converting

extracellular signals to intracellular signals (transmembrane signaling) Membránfehérjék Membrane Proteins Proteins confer specific functions to the membranes. Distinctive features of different kinds of membranes Types of membrane proteins: 1. Integral (intrinsic) membrane proteins 2. Peripheral (extrinsic) membrane proteins Membrane Proteins Structure of the β2 Adrenoceptor A plazmamembrán fehérjék funkciói Functions of Plasma Membrane Proteins - Transzport - Enzimatikus aktivitás - Szignál transzdukció - Intercelluláris kapcsolódás - Sejt-sejt közötti felismerés - Kapcsolat a citoszkeletonnal és az extracelluláris matrixszal TRANSPORT ACROSS BUT NOT THROUGH THE MEMBRANES Endocytosis - phagocytosis - pinocytosis -receptor-mediated endocytosis Exocytosis Fusion of membrane vesicles Receptor-Mediated Endocytosis Digestion of Substances in Pinocytic Vesicles Constitutive and Regulated Exocytosis HÍZÓSEJT HISZTAMINT SZABADÍT

FEL. HISTAMINE RELEASE FROM MAST CELL. A MOLEKULÁK MEMBRÁNON KERESZTÜL TÖRTÉNŐ SZÁLLÍTÁSA TRANSPORT OF MOLECULES THROUGH THE MEMBRANE • Diffusion • Osmosis • Protein-mediated membrane transport PROTEIN-MEDIATED MEMBRANE TRANSPORT A mediált transzport tulajdonságai Properties of Mediated Transport 1. Rapid transport 2. Chemical specificity 3. Competition between structurally related molecules 4. Inhibition by compounds that are not structurally related to the substrates 5. Saturation kinetics PROTEIN-MEDIATED MEMBRANE TRANSPORT 1. Facilitated transport (facilitated diffusion) is not linked to metabolic energy. 2. Active transport must be linked to energy metabolism in some way. - primary active transport - secondary active transport Na+/K+-ATPase maintains the intracellular Na+ and K+ concentrations in animal cells Muscle Ca2+-ATPase Pumps Ca2+ Ion From the Cytosol Into the Sarcoplasmic Reticulum Secondary and Tertiary Active Transport

Systems Transepithelial Transport Transepithelial Movement of Glucose and Amino Acids Requires Multiple Transport Proteins