Biophysics of the Cell PDF

Foreword  In the course of three months - our staff will guide you through the secrets of Me- - dical Biophysics Both lectures, and practicals are obligatory for students.  You will attend Lectures and Practicals according to timetable (your questions e.g. how to g...

Foreword  In the course of three months - our staff will guide you through the secrets of Me- - dical Biophysics Both lectures, and practicals are obligatory for students.  You will attend Lectures and Practicals according to timetable (your questions e.g. how to get credit, substitution in the case of illness, etc. are discussed with teachers during Practical sessions ) For Instructions to organization of study and details ask following teachers: Prof. Jakuš - head, Dr. Simera-vicehead  Content of study Covers following topics.: Biophysics of Cell, Transport membrane mechanisms, Resting and Action potentials , Muscle contraction, Synapse, Basics of respiration, Heart and circulatory sys- ems, Senses, Hearing, Vision. Changes in body due to action of mechanical an electromagnetic influences, Effects of Sound, Infrared and Ultravio- let radiations, Radioactivity, Diagnostic methods in human medicine: X-ray, Utrasound, Computer tomography, Magnetic tomography, etc. Therapy in human medicine, Biocybernetics, Modern Machines, Nanotechnology and many others. For more details look for my Lectures being available to see and download from our faculty homepage: www.jfmed.uniba.sk/index.php?id=3649  Study Literature - Source 1.Lectures – the content results from Professors experience, also from Textbook of Medical Biophysics (in Slovak ), also from Ganong´s Textbook of Physiology Content of some Lectures and Practicals ,Programme of Lectures, Requirements and condition how to obtain credits, points etc. are available on web.page: www.jfmed.uniba.sk/index.php?id=3649 2.Textbooks- Nave & Nave: Physics for Health Sciences,1985, Ronto,Tarjan et al.:An introduction to Biophysics with Medical Orientation, 1999, 3. Booklet- Kukurova et al.:Biophysical Elixir, 1991 4. Worksheet for Practicals Jakus,Poliacek, Simera :Practical Tasks in Medical Biophysics ,2013 , it contains theory and personal protocol to particular tasks.  Medical Biophysics. Biophysics of a Cell. Transport membrane mechanisms. Resting membrane potential. LECTURE 1 Ján Jakuš (www.jfmed.uniba.sk/index.php?id=3649) Martin 2014  Medical Biophysics is an interdisciplinary subject of medical scien- ces,explaining basic problems of a human body at a level of atoms, molecules, cells, tissues, and organs answers the physical problems that appear in biology, chemistry, anatomy, physiology... explains effects of radiation, giving rules and recommendations for their use and safety explains and creates new methods and devices for diagnosis and treatment of human diseases Medical Biophysics - kind of Medicine Science, a part of Biophysics  HUMAN CELL Definition: Cell is a basic anatomical and functional unit of the body with total number of 60.000 bilions and size from 4-120 µm (10-6 m). Number of cells composes tissues (206 bones ,600 muscles, thousands of nerves ), number of tissues builds organs (heart, lungs, kidney.. ) Typical signs of living cell: own meta- bolism, excitability, reproduction Composition: Cytoskeleton -surface membrane,cytoplasm, organelles (for details see our videos at Practical Sessions also look a book of Biology)  SURFACE MEMBRANE  Surface Membrane of RBC  Surface Membrane (SM) Intracellular SM- covers subcellular structures (e.g.Nucleus, Golgi complex, Mitochondria) Plasmatic SM - covers the surface of each cell Functions: semipermeability, division, protec- tion, integrative roles, transport of ions, source of enzymes, storage of electric charges, etc. Composition: SM is Phospholipid bilayer- 45% Hydrophilic heads (consisting of phosphates- soluble in water) Hydrophobic tails (consisiting of hydrocarbon fatty acids-insoluble in water- 45%). Proteins bilayer (peripheral, integral) - 50% , + Sugar + Cholesterol (5%) Heads are (+) electrically charged and directed towards the membrane exterior, tails are charged negatively (–), being oriented to membrane interior  Transport Membrane Mechanisms are responsible for movement of water and solutes across the cell membrane are of vital importance for cell metabo- lism, for production of cell electricity i.e. (resting and action membrane potentials) Types: PASSIVE - it does not need deli- very of a free energy. (Simple and Facilita- ted Diffusion, Osmosis, Filtration). ACTIVE - free energy from ATP is needed and must be delivered (Na-Kpump, Ca-pump, H-pump, exo/ endo-cytosis, and phagocytosis) Simple Diffusion through cell membrane  Simple Diffusion is a kind of passive membrane transport of H20, solutes, or gases (O2, CO2) from the space with a higher concentration towards the space with lower one (along the concentration gra- dient), untill the equilibrium is established. Total volume of solution does not change in both of spaces. Rate of diffusion:Fick Law: J = - d. conc.grad. [d- koeficient of diffusion] Generally: diffusion depends - linearly on a conc. gradient, solubility of a matter, and on ambient temperature Nonlinearly depends on a size of particles Types of diffusion: Simple, Facilitated, Throu- gh the protein channels Scheme of Facilitated Diffusion  Facilitated Diffusion is a passive transport mechanism of bigger molecules (e.g.aminoacids),along a concentration gradient, when substance binds to a protein carrier the carrier is protein placed within the membrane and undergoes a process of conformation (is a change of its chemistry) after binding of molecule and conformation, the carrier shifts (turns around ) and finally releases substance on an opposite site of a cell membrane Diffusion through the protein (ion selective) channels is a passive transport of ions Na+, K+, Ca2+, Cl- ,or low molecular soluble sub- stances through the protein channels within the membrane, along the concen- tration gradient Protein channels are :1.“voltage“gated - they are open or closed (gating) due to a membrane electricity,or 2.„ligand“gated- when e.g. a hormone binds to a channel, thus opening it. „Voltage“ and „ligand“ gated protein (ion selective) channels  Filtration is a passive transport of water and small particles from a space with higher hyd- rostatic pressure to a space with lower one the power that drives Filtration is Pressure gradient of a hydrostatic pressure (not a concentration gradient ! ) examples: filtration and resorption in capillary loop or in kidneys  Osmosis is kind of passive transport through the semipermeable cell membrane, when only water moves from a space with lower concentration (lower osmotic pressure) to a space with higher concentration (higher osmotic pressure), till to equilibrium.Total volume of solution in both compartments will change. Simply –water wants to dilute more concentrated solution (Van Hoff´s Law) normal osmolarity 300 mOsm/l- isotonic solution with blood plasma (e.g. 0.9 % NaCl, or 5% of glucose) Below 0.9%- hypotonic solution Above 0.9% - hypertonic solution example: Osmotic fragility of RBC ( see practicals ) OSMOSIS – scheme Changes in size of RBC due to osmosis (HAEMOLYSIS) ACTIVE MEMBRANE TRANSPORTS  transport of molecules among cells against the concentration, or electric gradients, a delivery of free energy from ATP is crucial. Classification: Primary active transport through the selectíve ions channels. Pumps : Na +- K+ pump (in all cells), Ca 2+- pump (in muscle cells), H+- proton pump (in cells of stomach producing HCl) Secondary active transport when a substance (e.g. glucose) binds on ion (Na+), then this complex (Na+ glucose) is carried through the membrane actively (the glucose-Na+ contransport), exo-/endo, phagocytosis Na+-K+ pump (Na+- K+ ATPase) Na+- K+ pump – scheme Na+-K+ pump (Na+- K+- ATP-ase) - It is an enzyme, placed within the cell membrane (number =106 molecules within a membrane of one neuron ) - it carries 3 ions of Na+ from inside to outside, and at the same time, 2 K+ from outside to inside of the cell - It can exchange max. 200 Na + and 133 K+ / sec. (maximal capacity of pump) - It requires delivery of free energy (from ATP) - It is important for renewal of electric charges on body cells Exocytosis, Endocytosis (Phagocytosis)  ACTIVE membrane transports.: Exocytosis and Endocytosis.  Exocytosis - “cell vomiting“ is a release of larger molecules by the protrusion of a cellular membrane, under delivery of energy and Ca2+ ions Endocytosis –“cell eating“ is an uptake of molecules by a cellular membrane, e.g. ingestion of bacteria by leukocytes (phagocytosis). It needs a delivery of energy, too. Resting membrane potential (RMP) It is an electric potential difference measured between (+) charged cell exterior and (–) charged cell interior. Its value is negative and equals to a Sum of Equilibrium Potentials of all 3 ions (K+, Na+, Cl-). is a result of membrane semipermeability i.e. different leakage of cell membrane for 3 main ions (K+, Na+, Cl-). permeability of cell membrane for ions at rest is: K+ : Na+ : Cl- = 1 : 0.04 : 0.45 K+ : Na+ : Cl- = 100 : 4 : 45 (%) Value of RMP for nerve cells is: -70 mV, sceletal muscle:– 90 mV, heart muscle:- 80mV, smooth muscle: -50 mV (non-stabile)  Equilibrium Potential (EP) is a value of electrical voltage that just stops the passive diffusion of ions (K+ ,Na+ ,Cl -) along their concentration gradients Cell Inside (-) charged Cell Outside(+) cha. (because PROTEINS inside) (because Na + outside) Concentration and electrical gradients of K+, Na+, Cl- ions OUTSIDE INSIDE  Nernst formula Each ion has its own Equilibrium Potential (mV) which can be counted: (Nernst counted it only for K+ )  Goldman´s Equation Sumation of all Equilibrium potentials (for K, Na, Cl ) results in a real value of Resting Membrane Potential ( e.g. V m = -70 mV for neuronal cells) Goldmann counted it for all 3 ions (their concentrations outside and inside) + the permeabilities of membrane for 3 ions. for comming and attention