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Revision for AS OCR Biology ­ Topic 2 (Cell Membranes)

Roles of the Cell (Plasma) Membranes:
Controls what substances go into and out of the cell partially permeable membrane.
For cell signaling and cell recognition.

Roles of the Membranes within cell:
Controls what substances go into and out of the…

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Proteins
Are transmembrane that act as carrier proteins and channel proteins.
Act as receptors for chemicals made by other cells.

Affect on the structure of phospholipid bilayer and the permeability:
Temp. below 0 degrees:
Phospholipds can't move as they have no energy, membrane is rigid. Increased permeability.

Temp. between 0…

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3) Releases the molecule on the other side of the membrane.

Channel Proteins:
Channel proteins form pores in the membrane for charged particles to diffuse through. Different
channel proteins facilitate the diffusion of different charged particles.

Active Transport
Active transport uses energy (ATP) to moves substances across a conc. Gradient…

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