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Cell structure - Plasma membrane - Membrane Proteins
Membrane Proteins
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| Description |
The hydrophobic central region of the membrane forms a barrier for hydrophilic and charged molecules. Membranes thus separate aqueous reaction spaces, the compartments, from one another. An exchange of substances between the compartments is achieved by membrane proteins.
Ion pumps transport ions against concentration gradients, in a process driven by ATP hydrolysis. Sodium-potassium ATPase, for example, cleaves 1 ATP molecule to transport 3 sodium ions out of the cell and 2 potassium ions into it.
Ion channels enable the diffusion of ions along their concentration gradient. Electrical, chemical or mechanical signals control channel opening and closing.
Signals are transmitted via membrane receptors. Some hormones bind to extracellular binding sites of their receptors. These then activate cellular reactions.
Membrane proteins can also have mechanical functions. Integrins connect the cytoskeleton with the extracellular matrix. They are externally linked to the collagen in the extracellular matrix. In actin filaments of the cytoskeleton they are internally anchored by coupling protein complexes.
Many membrane lipids and proteins, especially those on the outer side of the cell membrane, carry a glycocalyx that is a cell-specific composition of polysaccharide chains. The glycocalyx functions in cell recognition.
Duration: 02:30 min
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Sources
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BEREITER-HAHN, JÜRGEN; PETERS, WINFRIED S.: The Cell - Inner Boundaries - Membranes and Transport. CD-ROM C 7102. MMcD, Düsseldorf; interActive Systems iAS, Marburg, Berlin; IWF, Göttingen, 2002.
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Abbreviations
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Order |
This video is part of the CD-ROM The Cell - Inner Boundaries - Membranes and Transport. You can order it at the IWF Knowledge and Media gGmbH.
Also available as clip.
Order no.:
C 7159
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