Funbio 9 2024 Biological Membranes Transport PDF

Biological Membranes: transport I (macrotransfer) Class Foundation Year Course Fundamentals of Human Biology Code FUNBIO.9 Lecturer Dr Irene Oglesby Date 16th October 2024 Learning outcomes At the end of this lecture, the learner will be able to ALO1 - Recall the...

Biological Membranes: transport I (macrotransfer) Class Foundation Year Course Fundamentals of Human Biology Code FUNBIO.9 Lecturer Dr Irene Oglesby Date 16th October 2024 Learning outcomes At the end of this lecture, the learner will be able to ALO1 - Recall the difference between macrotransfer and microtransfer processes. ALO2 - Differentiate between exocytosis and endocytosis. ALO3 - Explain the mechanism of both phagocytosis and pinocytosis. ALO4 - Differentiate between receptor-mediated and fluid phase pinocytosis. or 5 fusion* ALO5 - Describe 4 stages in the secretory vesicles formation ALO 6 - Differentiate between constitutive and regulated secretion. MNB.X Lecture Title 2  Membrane Transport Macrotransfer Microtransfer Passive Active Exocytosis Endocytosis Constitutive Ca2+-dependent Phagocytosis Pinocytosis Receptor- Fluid- mediated phase Membrane Transport Macrotransfer The transport of macromolecules and larger items into and out of the cell which are referred to respectively as; Exocytosis Movement out of the cell Endocytosis Movement into the cell  EXOCYTOSIS –Process of releasing large biomolecules through the plasma membrane Membrane Transport –Accomplishes three tasks: 1. The surface of the plasma membrane Part 1: Exocytosis increases (by the surface of the fused vesicle). 2. The substances within the vesicle are released into the exterior. 3. Proteins embedded in the vesicle membrane are now part of the plasma membrane  Membrane Transport - Exocytosis 2 types of exocytosis: 1. Constitutive exocytosis (Non-Ca2+-dependent) 2. Ca2+-dependent exocytosis  Membrane Transport - Exocytosis Ca2+-mediated Exocytosis Requires the presence of Ca2+ in order for the vesicle to be released Important process in: –Neuronal communication Converts electrical information into chemical information (at the synapse) –Hormone release Insulin from beta cells  Exocytosis 1 Vesicle approaches plasma 1 Vesicle approaches plasma membrane, membrane, 1 Vesicle approaches plasma membrane, Vesicle approaches plasma 1 membrane, 2 fuses with it, and 2 fuses with it, and 2 fuses with it, and 2 fuses with it, and Hormone release 3 releases its contents outside cell. 3 releases its contents outside cell. Insulin from beta cells (as shown before) Figure 5-19 p124 3 releases its contents outside cell. Figure 5-19 p124 3 releases its contents outside cell. Figure 5-19 p124  Membrane Transport - Exocytosis Distinct steps in exocytosis vesicle snare 1. Vesicle trafficking 2. Tethering 3. Docking 4. Priming 5. Fusion 1. Vesicle trafficking - Movement of vesicles from site of production to the site of release Facilitated by: –Actin and microtubule-based cytoskeletons –Motor proteins (e.g. Kinesin, dynein)  Membrane Transport - Exocytosis 2. Vesicle tethering At the tethering point, a bridging complex is formed. by bridging proteins  Membrane Transport - Exocytosis 3. Vesicle docking Docking involves the attachment of the vesicle membrane with the cell membrane. It involves the holding of two membranes within a bilayer's distance of one another (