| 1.
Hydrogen-bonding between water molecules is the cause
of water's unique physiochemical properties. A water
molecule can interact with four neighboring water molecules. |
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| 2.
Molecules that cannot make H-bonds are insoluble in water;
the larger such a molecule, the more insoluble. Such
molecules are termed hydrophobic. |
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| 3. Lipids are
a diverse class of molecules grouped based on their insolubility
in water. Of particular importance in biology are
the amphipathic lipids,
which contain two domains, one capable of
making H-bonds, the other not. The ability to make H-bonds
makes a region hydrophilic. |
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| 4.
When dispersed into aqueous
solvent, amphipathic lipids can self-assemble
into higher order structures such as micelles and bilayers.
In these states, the lipid's hydrophilic domain
interacts with water while its hydrophobic domain(s)
are removed from contact with water. |
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| 5.
The primary boundary layer of a cell, the plasma
membrane, is based on the ability lipids
to self-assemble. |
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| 6.
The plasma membrane poses a barrier to the movement of
hydrophilic molecules into and out of the cell |
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| 7. Proteins within
the plasma membrane regulate molecular movements into
and out of the cell. |
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| 8.
Within the plasma membrane is a concentrated solution
of proteins and other small and macromolecules, the cytoplasm. |
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| 9.
Energy can be stored in the form of chemical
gradients across the membranes. |
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| 10.
The high concentration of cytoplasmic components leads
to osmotic
effects across the plasma membrane. |
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