BSC 314 Lecture Notes - Lecture 21: Sucrose, Hydrophile, Exocytosis
27 Jun 2018
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Membrane Structure
The plasma membrane on the outer surface of the protoplast regulates what enters
and leaves the cell. Other membranes within the cell compartmentalize the protoplast,
separating the interior into units of differing chemical composition, each with their
own differentially (selectively) permeable membranes—membranes, like the plasma
membrane, that selectively permit the passage of some materials while inhibiting the
passage of others. (A freely permeable membrane that allowed everything to pass
would be useless for the cell as would an impermeable membrane that allowed
nothing to pass.) The cell is thus a collection of “factories” that import, manufacture, and
export metabolic substances and that are separated from one another by membranes.
The membranes are channels of communication within and between cells and carry the
directions supplied by the genes in the nucleus. Signals transmitted via specific
molecules that institute reactions in their receptors organize the individual cells into an
integrated multicellular organism. All of the cellular membranes are essentially alike in
structure, but differ in their constituent proteins. Consequently, they vary in the types of
materials they recognize and in the reactions they initiate and conduct.
The currently acceptable version of membrane structure is the fluid mosaic model‐,
which visualizes the membrane as a double layer of fluidlipids in which proteins float
laterally, forming a changing mosaic pattern (refer to Figure ).
Figure 1
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Document Summary
The plasma membrane on the outer surface of the protoplast regulates what enters and leaves the cell. The cell is thus a collection of factories that import, manufacture, and export metabolic substances and that are separated from one another by membranes. The membranes are channels of communication within and between cells and carry the directions supplied by the genes in the nucleus. Signals transmitted via specific molecules that institute reactions in their receptors organize the individual cells into an integrated multicellular organism. All of the cellular membranes are essentially alike in structure, but differ in their constituent proteins. Consequently, they vary in the types of materials they recognize and in the reactions they initiate and conduct. The currently acceptable version of membrane structure is the fluid mosaic model which visualizes the membrane as a double layer of fluidlipids in which proteins float laterally, forming a changing mosaic pattern (refer to figure ).
