RCSI FUNBIO.8 Biological Membranes Transport I (Microtransfer) PDF

Fundamentals of Human Biology FUNBIO.8 Biological Membranes: Transport I (microtransfer) Prof Warren Thomas D AT E : 6 t h O c t o b e r 2 0 2 4 Fundamentals of Human Biology FUNBIO.8 Biological Membranes: Transport I (microtransfer) Prof Warren Thomas D AT E : 6 t h O c t o b e r 2 0 2 4...

Fundamentals of Human Biology FUNBIO.8 Biological Membranes: Transport I (microtransfer) Prof Warren Thomas D AT E : 6 t h O c t o b e r 2 0 2 4 Fundamentals of Human Biology FUNBIO.8 Biological Membranes: Transport I (microtransfer) Prof Warren Thomas D AT E : 6 t h O c t o b e r 2 0 2 4 Learning outcomes At the end of this lecture, the learner will be able to; Contrast and compare the intracellular and intercellular environment. Differentiate between macrotransfer and microtransfer processes Describe passive diffusion processes and the role of membrane transport proteins. Differentiate between transporter and channel proteins. Explain facilitated transport. Describe mechanisms of active transport in cell membranes. Explain how glucose enters the cell by means of a sodium dependent co-transport carrier system. MNB.X Lecture Title 2  · water moves through chennels. Membrane Transport This involves the transport of Membrane Transport substances across the plasma membrane Loading… Nutrients and O2 must be taken in and CO2 and the waste products of cell metabolism must be removed from the cell https://byjus.com/biology/transport-across-cell-membrane/  Membrane Transport - Intracellular vs. Intercellular Cell survival depends upon: 1. Exchange between neighbouring cells 2. Exchange within the cell itself, i.e. the intracellular environment 3. Exchange between the surrounding intercellular medium i.e. the extracellular matrix Inter – between cells Intra – inside/within cell Basics of Cell Signalling; application.wiley-vch.de  Membrane Transport Two general mechanisms are involved: Macrotransfer Transport of macromolecules Only brings materials into endosomes or lysosomes within the cytoplasm Loading… For molecules to be absorbed into the cytoplasm they must cross the surrounding membrane Microtransfer Transfer of small molecules and ions across cell membranes, both internal and external  Membrane Transport Macrotransfer Microtransfer Passiv Activ requires enegs) Comeees) e e Exocytosis happensthe Endocytosis Constitutive Ca2+- Phagocytosi Pinocytosis dependent s Receptor Fluid- - phase mediated Active Transport  Membrane Transport - Microtransfer Microtransfer of biomolecules can be by two different mechanisms: This is This is easy hard work 1. Passive transport C – No energy required o e.g. Simple diffusion n c e 2. Active transport n – Requires energy tr at i ACTIVE PASSIVE o n g r a d  ie Passive Transport No energy required 1. Passive Transport  Membrane Transport - Microtransfer Passive transport (Diffusion) The tendency for all molecules in liquids and gases to move in all directions until they are evenly distributed in the available space "All Khan Academy content is available for free at www.khanacademy.org". Brownian movement: The particles must be less than 2µm This process does not require energy  Membrane Transport - Microtransfer Diffusion is dependent on movement of molecules, due to their kinetic energy, from regions of high concentration to low concentration It will occur whenever such a concentration gradient exists Movement ceases when the equilibrium constant reaches 0  Membrane Transport - Microtransfer This requires the membrane to be freely permeable to the molecules and ions at the time in question Water and small non-polar molecules (O2, CO2) pass freely through the plasma membrane by diffusion Loading… →Molecules diffuse across the membrane by passive transport lique gases only https://www.youtube.com/watch?v=cs8ud7Eh7ko Membrane Transport - Microtransfer 2. Facilitated transport Glucose and other molecules (amino acids, nucleotides) enter some animal cells by a process of facilitated or mediated diffusion. This uses a set of carrier proteins: Specific permeases which are highly selective often transporting only one type of molecule. Undergo conformational changes to transfer the bound solute. These facilitate the transport of sugars, amino acids and nucleotides. It is essentially a passive transport system, as no energy is required. Figure 5-14 p119 https://www.youtube.com/watch?v=IX-kLh34KcQ  What affect rates of facilitated diffusion? 1. Saturation of the carrier binding sites 2. The concentration gradient Saturation - Since the number of carrier proteins in the membrane is limited, once all the proteins are bound, they can no longer bind more molecules. At this point, the rate of the diffusion cannot be increased even with the increase in the concentration gradient.  > primary (depends - Energy required use of on a ATP pamp by Macromolecules and charged ions (H+, the 2. Active Transport Na+, K+, Cl-) do not pass freely through directly depended cell membranes Y secondary on : not a pump selective ; needs These molecules require it the useaof pores or channels secondary transporter Special class of transmembrane proteins called membrane transport proteins  protein pumps - are Membrane Transport - Microtransfer imp for stomaca Active transport is energy dependent and requires the expenditure of Adenosine Triphosphate (ATP) molecules Active transport systems are usually inhibited by low temperatures The best studied active transport systems involve inorganic ions, amino acids and monosaccharides; Most models postulate that integral transmembrane proteins act as carriers translocating the substance from one surface to another  Membrane Transport - Microtransfer Primary active transport Typically moves molecules against their electrochemical H+ H+ H+ H+ gradient. low- high H+ H+ H+ H+ Uses energy in the form of ATP Secondary active transport. Moves molecules together – this transport enables one molecule to move along its electrochemical concentration ATP H+ H+ ADP + Pi gradient and generate energy to transport second molecule H+ H+ from low concentration to high concentration Symport (in the same direction) E.g. Na+-dependent co-transport carrier system Antiport (in opposite directions) A Model of a Proton Pump Proton pumps use the energy of ATP to transport protons (hydrogen ions) across membranes. The energy of the electrochemical gradient established can then be used for other processes. Figure 5-17 p122  Active Transport - Symport Sodium-Dependent Co-transport Carrier System Well studied in intestinal epithelial cells Drives the movement of glucose, other monosaccharides, amino acids and pyrimidines into the cell NB: Glucose molecules are co- transported against their concentration gradient  Active Transport – Antiport System Most membranes incorporate an ATP- driven sodium/potassium pump (Na+/K+-ATPase), which maintains a Na+ gradient Transports: 3 Na+ ions from inside to out 2 K+ from outside to in 1 ATP hydrolysed Active Transport – Antiport System Figure 5-16b p121 What does the secondary active transport use? 1. ATP es 2. Concentration gradient of a metal ion eg Na+ Secondary active transport. Moves molecules together – Enables one molecule/ ion to move along its electrochemical concentration gradient (eg Na+) and generate energy to transport second molecule/ ion (eg glucose, amino acids) from low concentration to high concentration Thank you F O R M O R E I N F O R M AT I O N P L E A S E C O N TA N T Prof Warren Thomas EMAIL: [email protected]