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Membrane Transporters - Coggle Diagram

- - - - its partition coefficient K is irrelevant because transported molecule never enters hydrophobic core of phospholipid bilayer
        
        Transport via limited number of uniporter molecules. Maximum transport rate Vmax depends on number of uniporters.
        
        Transport is reversible, direction of transport will change with concentration gradient.
        
        Transport is specific. A measure of the affinity of a transporter for its substrate is Km =
        substrate concentration at which the transport is occurring at half Vmax.
  - - - GLUT1
        
        catalyzes net import of glucose into cell
        
        Kinetics can be described by simple enzyme-catalyzed chemical reaction
        
        Sout + GLUT1 ⇌(Km) Sout - GLUT1 ⇌(Vmax) Sin + GLUT1
        
        Km: the conc. of substrate at which transport is half maximal
        
        Determines the affinity!
        
        1 more item...
        
        Sout - GLUT1 => GLUT1 in the outward-facing conformation with a bound sugar
        
        alternates between two conformational states (out, in)
        
        = alternating access model
      - 12 α :pancakes::droplet:
        
        structures very similar, but
        
        differential expression in different cc types
        
        specific regulation of numbers on cell surface
        
        isoform-specific properties
      - GLUT3 🧠
        
        low Km for glucose
      - GLUT2 🍔
        
        Km of ~20 mM, rate of glucose influx will almost double after a meal, triggers secretion of insulin
      - GLUT4 :muscle:
        
        cells respond to insulin by increasing their uptake of glucose, thereby removing glucose from the blood
        
        different regulation of glucose metabolism in different cells while maintaining constant glucose concentration in blood
        
        no insulin
        
        GLUT4 in intracellular membranes
        
        insulin
        
        internal membranes fuse with PM, increasing number of GLUT4 on the cell surface, thus rate of glucose uptake
        
        defects in translocation to PM:
        
        type II diabetes 👹
      - GLUT5 :apple:
        
        only GLUT protein with high specificity (preference) for fructose
        
        fd on apical membrane of intestinal epithelial cells
        
        transports dietary fructose from intestinal lumen -> inside cells