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Chapter 2


Cell Membranes ­ Summary Notes
Structure

Plasma membrane:
Separates cell contents from external environment
Controls what passes between cell and environment
Partially permeable
Phospholipid bilayer
Membranes:
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
Method:
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…

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Chapter 2

Endocytosis:
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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