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Chapter 2

Cell Membranes ­ Summary Notes

Plasma membrane:
Separates cell contents from external environment
Controls what passes between cell and environment
Partially permeable
Phospholipid bilayer
Produce different compartments within cells
Important in cell signalling
Allow electrical signals to pass along them
Provide attachment site for enzymes/other molecules…

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Chapter 2

Receptor in plasma membrane interacts with Gprotein
Gprotein = activated
Activates enzyme
Causes response in cell
Receptor is also an enzyme ­ contains 2 parts
Signal molecule slots into both parts
Connection forms active enzyme
Enzyme causes response in cell

Membrane processes

Passive processes ­ don't require…

Page 3

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Chapter 2

Moving substances into cell
E.g. Phagocyte engulfing bacterium
Cell extends `fingers' of cytoplasm around bacterium
Fuse to form complete ring ­ vacuole
Enzymes secreted in to digest bacterium
Process can move liquid into cell
Exo/endocytosis ­ both active processes ­ require energy
Membrane permeability:
Affected by temperature…


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