The figure below shows a
section through part of the fluid mosaic model of the cell surface membrane
with a Na+/K+ pump protein.
a)
Explain why the cell surface membrane is
described as a fluid mosaic.
The cell surface membranes is
described as a fluid mosaic due to the scattered mosaic arrangement of proteins
that float in the phospholipid bilayer. The bilayer is fluid as the lipid and
proteins molecules can move laterally and rotate on their axis.
b)
Describe how the channel surface of the protein
differs from its surface next to the phospholipid tails.
The channel
surface is hydrophilic to allow the passage of ions. The surface next to
phospholipid tails is hydrophobic in order to interact with the hydrophobic
fatty acid tails so that the protein stays in the membrane.
c)
Explain why Na+ and K+
cannot pass freely across the phospholipid bilayer.
Na+ and K+
cannot pass freely across the phospholipid bilayer because the bilayer is
impermeable to ions. The hydrophobic tails in the phospholipid bilayer repel
the ions, hence transport of the ions requires the Na+/K+
pump.
d)
Cholesterol and glycolipids are associated with
the cell surface membranes.
Suggest one function of each compound in
membranes.
Cholesterol:
Functions as a plug to reduce the entry and exit of polar molecules across the
cell
surface membrane.
Glycolipid: Functions
in cell-cell recognition, acting as receptor sites for chemical signals.
by qian ying
No comments:
Post a Comment