Homeostasis A - Membrane Transport Mechanism -Updated.pdf

Tran Homeostasis-A Cell Membrane Transport 2 Mechanisms 11 Physio I 2 Unit I- Problem 2 3 ...

Tran Homeostasis-A Cell Membrane Transport 2 Mechanisms 11 Physio I 2 Unit I- Problem 2 3  They Rhinocytos Week 2 - Homeostasis A Problem 1: a.EE A 9-month-old boy is brought to the emergency department 1. Guyton, Textbook of Medical with a chief complaint of diarrhea and vomiting for 2 days. Physiology 14th Ed., (2021). He has a fever, tachycardia, and an increased respiratory rate. The anterior fontanel is sunken, and his skin turgor is slightly diminished. He is given intravenous glucose saline in the Transport of substances through cell emergency department and is then hospitalized for further membrane, Chap. 4 Pp. 51 – 62. management. Body fluids compartments, Chap. 25 Pp. 305 – 316. Problem 2: An 86-year-old man was admitted to the hospital because he 2. Lab 2 in Physiology Manual (Practical) had become lethargic, confused, and was refusing to drink 3. Lab 3 in Physiology Manual fluids. On admission, his skin felt hot and doughy, his eyes were sunken, and his mouth was dry. Serum electrolytes (Cases/Calculations) revealed hypernatremia, hyperchloremia, and increased plasma osmolarity. 5% glucose in saline solution was given intravenously as prescribed. Learning Objectives List the primary functions of the cell membrane Describe the selective membrane permeability and how substances move across cell membranes List the transport mechanism of macromolecules: Endocytosis ( phagocytosis / pinocytosis) and exocytosis. phinecytosis Receptor mediatch phagocytosis Cytosis 9/16/2024 3 General Functions of Plasma Membranes Important for maintaining homeostasis, for example, ion distribution Separates intracellular fluids from extracellular fluids Signal transduction Cell recognition by glycoproteins on the outside of the cell Transport of substances across Glycocolyx importantfor maintaining homeostasis ie iondistribution 1 transduction 2 Signal Separates the ECF from the ICF 3 Allowthe substance to across 9 cell recognition 9/16/2024 outside 4  ohecel Downa 9 Cabsfayc.cl energy Types of Membrane Transport heaqpassive independent mediafire.neetaaga.int eekfmidActiveenengy Gradient iii Passive Transport Active Transport gradient is Occurs down electrochemical gradients Occurs against a concentration gradient more energy Either no mediator is needed 0 Involves a “carrier” (Simple diffusion) or involves Requires additional energy a “channel” or a “carrier” Primary or secondary (facilitated diffusion). active transport No additional energy (ATP) required (just kinetic energy) Mediator chaff facilitator 00 0 onlykinetic 9/16/2024 energy 5  Simple Diffusion Extracellular fluid Membrane Lipid Molecular Concentration surface area solubility size outside cell Fick’s law of diffusion Membrane Concentration thickness gradient Diffusion.gg fotionalto Composition of lipid layer membranepermeability Intracellular fluid Concentration inside cell 2 Surface area Fick's Law of Diffusion says: gratify surface area concentration gradient membrane permeability Concentration Rate of diffusion 3 membrane thickness reversibly proportional Membrane permeability to Membrane Thickness lipid solubility Membrane permeability molecular size Changing the composition of the lipid layer can increase or decrease membrane permeability. Facilitated Diffusion: Passive Transport Aided by Proteins In facilitated diffusion, transport proteins speed the movement of molecules across the plasma membrane E Type of transport proteins: A. Channel proteins provide corridors that allow a specific molecule or ion to cross the membrane. B. Carrier proteins undergo a subtle change in shape that translocates the solute-binding site across the membrane. - Involves the transport of hydrophilic molecules such as ions, glucose, and amino acids. 9/16/2024 7  Stead 0 8 Eos 565 Gating of Channel Proteins Have receptors pressure a 6 8 cat  Facilitated Diffusion: Carrier Mediated Diffusion Substances move down their chemical and electrical gradient. Not linked to metabolic energy carrier Saturation kinetics: rate of diffusion approaches Vmax or Tmax. A Chemical specificity: glucose, amino acids. 14 GLUT for glucose; Insulin increases rate of glucose facilitated diffusion by activation of GLUT4. B low concentration i facilitated I Vmax 6H45 52 9/16/2024 10 Primary Active Transport 0 The proteins (carriers) involved in primary active transport require energy in the form of ATP to transport substances against their 03 concentration gradients. Direct use of energy Antiport Na+- K+ ATPase pump Carrier transporting ions against electrochemical gradient (uphill). Carrier is an enzyme that hydrolyzes ATP. Inhibited by metabolic inhibitors. F Coupling ratio (3 Na+:2K+), thus electrogenic pump Creates an electrical potential across cell membrane and contributes less than 10% to the membrane potential. Plays an important role in the osmotic balance of cells and controls cell volume. 9/16/2024 11 Other ATPases: Ca++ Pump and H+ Pump cell membrane sarcoplasmicreticulum Ca2+ ATPase Present on the cell membrane H+ ATPase and the sarcoplasmic reticulum Found in parietal cells of gastric glands Maintains a low cytosolic Ca2+ (HCl secretion) and intercalated cells of concentration renal tubules (controls blood pH). secretion HCl vk.INT membrane parietal celletrician Cell 9/16/2024 reticulum Wintercalatedells Candidates 12  s oplasmordenham Secondary Active Transport: Na+ Co-Transport Moves substances against electrochemical gradients IS This is secondary active transport because it is dependent upon the diffusion gradient for Na+ spent Atport created by the Na+/K+ pump (Transport is driven by the energy stored in the concentration gradient of another molecule (Na+)). Energy for transport is indirectly provided by the Na+- K+ ATPase pump (Indirect use of energy) Thus, indirectly, all secondary active transport processes are diminished by inhibitors of the Na+- K+ ATPase because their energy source, the Na+ gradient, is diminished. 9/16/2024 13  Types of Secondary Active Transport gymont 1. frat Co-transport (symport): Solute moves against concentration gradient (up hill) in the same direction as Na+ ions. Example : Glucose-Na+ cotransport in the intestinal epithelium 2. Co-transport (antiport): Solute moves in the opposite direction of Na+. Examples:  Uphill extrusion of Ca2+ from a cell by a type of pump that is coupled to the passive diffusion of Na+ into the cell. a  Hydrogen Sodium exchange in the kidney tubule. Cat we 9/16/2024 Not 14 Other Mechanisms of Membrane Transport Paracellular transport: Movements of ions and water through the junctions between cells (epithelial cells in the kidney tubules, or in the GI tract). Solvent drag: Water is reabsorbed by osmosis and carries all other solutes along. F Endocytosis: is the process of capturing a substance or particle from outside the cell by engulfing it with the cell membrane and bringing it into the cell. Exocytosis: describes the process of vesicles fusing with the plasma membrane and releasing their contents to the outside of the cell. Both endocytosis and exocytosis are active transport processes. 9/16/2024 15 Endocytosis – Pinocytosis and Phagocytosis I Pinocytosis: “Cell-drinking” Phagocytosis: Endocytosis of fluid and small particles Endocytosis of large molecules (generally larger than 0.5 μm associated with the engulfed fluid. in diameter), such as bacteria, dead cells, and tissue debris. Invagination of membrane and Monocytes or macrophages formation of pinosome. 9/16/2024 16 Receptor Mediated Endocytosis 1. Receptors cluster in regions termed coated pits, as they are coated with proteins such as clathrin. Clathrin causes the coated pit to invaginate and become a vesicle, bringing the desired ligand into the cell. This process can be hijacked to allow for toxins and viruses (Opportunistic ligands) to enter the cell. 2. Requires energy (active process) and Ca++ in ECF. Exocytosis  Ejection of substance from the cell.  Requires energy and Ca++.  Secretary products of endoplasmic reticulum to Golgi apparatus.  Release of neurotransmitters  Release of hormones 9/16/2024 18