Carrier All
Posted on Friday, October 9th, 2009 at 10:26 pm
which of the following is a characteristic feature of all carrier proteins in the plasma membrane?
a) they all exibit specificity for a particular type of molecule.
b)they are all peripheral membrane proteins
c) they all work against the diffusion gradient
d) they all require the expenditure of a cellular energy to function
e) they all have few, if any, hydrophobic amino acids
The Answer is A.
Why the rest are not correct :
B) There are transmembrane proteins as well for exocytosis and endocytosis.
C)Not all are due to osmosis or diffusion. There are some for active transport. Eg. The microvilli in the small intestine for absorbing food and nutrients. These are done via active transport and need energy.
D) Those that work via a diffusion gradient doees not need energy.
E) Transport proteins do consist of a number of hydrophobic amino acids. It’s just that due to folding of the polypeptide to become the shape of the transmembrane protein, it is not hydrophobic in nature as the hydrophobic amino acids are packed away.
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