cell membrane functioning 1-membrane transport - copy.pdf

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).


cell membrane functioning 1-membrane transport - copy.pdf

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