cell membrane functioning 1-membrane transport - copy.pdf
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7/28/2019 Cell Membrane Functioning 1-Membrane Transport - Copy.pdf
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Cell Membranes Function asIntegrative Systems
Understanding how cell membrane molecules cross-
talk in membrane functioning
Cell Membranes Allow Exchangesof Substances and
1. Membrane transport2. Cell signaling
Dr. Mircea Leabu, Membrane Transport (lecture iconography)
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Membrane transport
Transport through membraneions and small molecules (
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Simple Diffusion
Facilitated Diffusion
1. Uniport transport one ion (molecule) transported;
2. Coupled transport (co-transport) several ions (molecules)simultaneously transported
- symport ions (molecules) all transported in the same direction- antiport at least one ion (molecule) transported in opposite direction
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GLUT1,example for uniport transport
found in erythrocyte membrane and most of animal cells
Erythrocyte GLUT1: ~45 kDa, 12 -helixes containinghydrophobic amino acids, and some Ser, Thr, Asn, Gln
SGLT1 (glucose transporter in enterocytes)example of symport transport
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Ion Channels
- Voltage-gated (voltage-operated)- Ligand-gated (ligand-operated)
- Mechanically gated (mechanically operated
Cyclical conformations of channels
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Cross-talk of various channels atneuromuscular junction level
Na+/K+ATPase (Na+/K+pump)example of active transport
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Cross-talk of membrane transportproteins, in enterocytes
Transport with membrane
Endocytosis: Phagocytosis
Pinocytosis: Constitutive Receptor mediated
Potocytosis
Exocytosis
Transcytosis
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Phagocytosis
Pinocytosis constitutive / potocytosis
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Receptor-mediated Endocytosis
The structure of clathrin coatClathrin organizes triskelion structures
Triskelion contains three large and three small polypeptide chainsTriskelions assemble in a basketlike framework as a convex cage
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SUMMARY
Cell membrane acts as an integrative systemby cross-talking of all molecular components in
order to allow exchanges with theenvironmental
Substance exchanges are done by membranetransport: Simple diffusion (nonpolar molecules, small polar
molecules);
Facilitated diffusion (ions, large polar molecules);
Vesicular transport (macromolecules andparticulate materials).
Dr. Mircea Leabu, Membrane Transport (lecture iconography)
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