11a+–+transport.2015 - Chapter 11 transport Membranes...

Info icon This preview shows pages 1–8. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 11 - transport Membranes restrict flow of things in / out Ions, polar molecules bigger than 150 D, or anything “big”
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Diffusion is spontaneous due to increasing entropy Requires facilitated transport
Image of page 2
3 Integral membrane proteins allow things to pass - come in 3 generic classes: pumps utilize external energy [ATP, light, redox] to move ions to create a gradient Slow to modest rates > need to “grab” energy, grab the specific thing, then move it across, return to setup . . . . . 10 1-3 carriers - transporters passively move solutes across, still follow enzyme kinetics in some cases link the movement of one solute down gradient with the movement of another up its gradient . . . . . . Symporter and antiporter each conformational change allows set # of molecules across A bit quicker but still modest – grab the solute, change conformation, return to setup – 10 3-4 channels ion specific pores that usually open/close in regulated fashion, when open – thing quickly moves passively through – very fast although temporary . . . . Up to 10 8
Image of page 3

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Blood sugar 5mM and ~10mM after meal So GLUT1 is at 77% peak after meal, while liver’ s GLUT2 version still only at 25% of its peak rate – thus very efficient at moving glucose into liver cells Glucose converted to G-1-P after entry Can be saturated
Image of page 4
5 MFS famil y Major Facilitator Superfamily 12H Hundreds of transporters identified ~third belong to the MFS family Are reversible – mechanism? uniporters move a single solute down gradient Ex. > GLUT1 moves D-glucose into cells /found on RBC membranes – glucose is used in the cell so disappears stops when gradient gone – saturatable with a Vmax 10 -1 to 10 3 >> up to ~1000/sec substrate binds to and waits for conformation shift where it is released on the other side Human genome has 14 versions – all have 12 spanning helixes
Image of page 5

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
6 structure of transporters vast majority have 12 transmembrane  helixes. front 6 are homologous [~30%] to the back six suggesting internal duplication of gene – some carriers [perhaps more ancient] that have only 6H form dimers. this genetic event allowed front and back to diverge and specialize both N and C terminus of protein are cytoplasmic mutation analysis of lacY suggest 6 helixes form passageway which solute binds to and then conformation change allows passage – substitutions to cys on inside surface alters substrates solute binds one side, inducing conformational change, allowing it to be released on the other side speed depends on gradient – can be saturated though because recognition and binding must occur GLUT mechanism is unknown - assumptions can be deduced TM helix aa facing outward are hydrophobic TM aa facing inward include S, T, N, and Q allowing the sugar to hydrogen bond to the passageway. A bit more channel like than the other transporters. Binding in groove produces conformational change that allows solute out the other side.
Image of page 6
Different isoforms of GLUT GLUT1 – erythrocytes and other cell types
Image of page 7

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 8
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern