Transport Across Cell Membrane-II PDF

‫بسم الله الرحمن الرحيم‬ TRANSPORT ACROSS CELL MEMBRANE-II Dr Nisreen Daffa Alla M.B.B.S, Ph. D, MSc Health Profession Education  Objectives Describe how energy from ATP hydrolysis is used to transport ions against their electrochemi...

‫بسم الله الرحمن الرحيم‬ TRANSPORT ACROSS CELL MEMBRANE-II Dr Nisreen Daffa Alla M.B.B.S, Ph. D, MSc Health Profession Education  Objectives Describe how energy from ATP hydrolysis is used to transport ions against their electrochemical concentration differences Explain how energy from the Na+ and K+ electrochemical gradients across the plasma membrane can be used to drive the net “uphill” (against a gradient) movement of other solutes. Describe the characteristics of carrier-mediated transport, and distinguish between simple diffusion, facilitated diffusion, and active transport Describe the process of vesicular transport  Active Transport Active transport Moves a substance against its concentration gradient Low high Requires a carrier molecule Requires energy  Types of Active Transport Active Transport 1. Protein Pumps Primary active transport – Requires direct use of ATP Secondary active transport – Driven by an ion concentration gradient established by a primary active transport system 2. Vesicular transport Endocytosis Exocytosis  Primary Active Transport Movement against concentration gradient Hydrolysis of ATP directly required for the function of the carriers. Molecule or ion binds to “recognition site” on one side of carrier protein. Carrier protein undergoes conformational change. – Hinge-like motion releases transported molecules to opposite side of membrane. Primary Active Transport  Na+/K+ Pump example to primary active transport Carrier protein has enzymes activity ( ATPase) Extrudes 3 Na+ and transports 2 K+ inward against concentration gradient. https://youtu.be/xjNW6LgPJVY AMBOSS  Na+/K+ Pump Steep gradient created by this pump serves following functions: Provides energy for “coupled transport” of other molecules. Involvement in electrochemical impulses. Promotes osmotic flow.  Secondary Active Transport Transport of two or more solutes are Coupled The use of the electrochemical gradient generated by primary active transport of one type of molecule to move another type of molecule against its gradient. Does not directly require ATP. Includes symporters (e.g., the sodium- glucose symporter) and antiporters (e.g., the sodium–hydrogen antiporter).  Secondary Active Transport Cotransport (symport): – Molecule or ion moving in the same direction as Na+. Countertransport (antiport): – Molecule or ion moving in the opposite direction of Na+.  Cotransport/symport The Na+/glucose cotransporter (SGLT1) is found in the apical membrane of epithelial cells of the small intestine and renal proximal tubules. Antiport/Counter transport  Vesicular transport across membrane Exocytosis Endocytosis Vesicular transport across cell membrane Endocytosis: taking bulky material into a cell Uses energy Cell membrane in- folds around food particle “cell eating” forms food vacuole & digests food This is how white blood cells eat Vesicular transport across cell membrane 3. Exocytosis: Forces material out of cell in bulk membrane surrounding the material fuses with cell membrane Cell changes shape – requires energy EX: Hormones or wastes released  Vesicle-mediated transport Vesicles and vacuoles that fuse with the cell membrane may be utilized to release or transport chemicals out of the cell or to allow them to enter a cell. Exocytosis is the term applied when transport is out of the cell. 18 Summary video  Complete the table Transport mechanism Characteristics Passive Vs active transport Simple diffusion through the lipid bilayer No need for energy+ carrier protein Protein pump+ energy(ATP) Exocytosis taking bulky material into a cell Mention types of passive and active transport  Complete the table Substance Transport mechanism Glucose absorption in intestinal cell Glucose reabsorption in renal cell Na+/K+ Pump Hormones or wastes released from cell white blood cells eat bacteria Transport Characteristics Example to mechanism substances transported by this mechanism Passive transport No need of energy O2, CO2, fatty acid. From high to low area Water of concentration Simple diffusion: 1. Lipid soluble O2, CO2, fatty acid. transport across the particles Small lipid bilayer size particles— less than 0.8nm. 2. Non charged particles Osmosis Water moves from Water area of highwater concentration to low water concentration Or from area of low solute concentration to area of high solute concentration Transport Characteristics Example to mechanism substances transported by this mechanism Facilitated diffusion Passive diffusion Glucose entry into fat Use carrier protein cells, brain cells etc Active transport Moves a substance Na+/K+ Pump against its concentration Glucose gradient. From Low to reabsorption in high renal and Requires protein pump intestinal cells Requires energy (ATP) Primary active Moves a substance Na+/K+ Pump transport against its concentration gradient. From Low to high Requires a protein pump (ATP) Requires energy Transport Characteristics Example to mechanism substances transported by this mechanism Secondary active Transport of two or Glucose transport more solutes are reabsorption in Coupled renal and Moves a substance intestinal cells against its concentration gradient. From Low to high Requires a carrier molecule Hydrolysis of ATP by Na+/K+ pump required indirectly to maintain [Na+] gradient. Endocytosis taking bulky material white blood cells eat into a cell bacteria Exocytosis Forces material out of Hormones or wastes cell in bulk released from cell  References Human physiology by Lauralee Sherwood, fifth edition Text book physiology by Guyton &Hall,11th edition Text book of physiology by Linda.s contanzo,third edition https://youtu.be/xjNW6LgPJVY 25