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Biological Membranes
The roles of membranes within cells and at the surface of cells, including the roles of membranes

- Partially permeable barriers between the cell and its environment, between organelles and
the cytoplasm and within organelles: Membranes are structures that separate the contents
of the cells from their…

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Intrinsic proteins/integral proteins: they are embedded through both layers of a membrane. They
are able to stay in place due to the interaction of their amino acid hydrophobic R-groups with the
hydrophobic core of the membrane. 2 intrinsic proteins are:

Channel proteins: provide a hydrophilic channel allowing the passive movement…

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Because alcohol is less polar (and in some cases not polar at all) it can pass through the
membrane and their presence between the phospholipids disrupts the membrane. When
the membrane is disrupted it becomes more fluid and permeable. This disrupts the cell from
being able to carry out its…

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Carrier proteins are involved too, these change shape when a specific molecule binds to

Rate of facilitated diffusion affected by: temperature, concentration gradient, membrane surface
area and thickness, the number of channel proteins present (more channel proteins = higher rate of

Active transport: Active transport is the movement…

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The diffusion of water into a solution leads to an in the volume of said solution. If the
solution is in a closed system (ex: cell) this leads to an increase in pressure ­ called
hydrostatic pressure ­ at a cellular level this pressure is large and potentially damaging



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