Changes

Transport proteins allow hydrophillic molecules, which are too large to get through water filled protein channels, to passively cross the membrane.  The molecules bind to protein and then the protein changes shape depositing the molecule at the other side of the membrane.  This transport method is also known as '''Facilitated Diffusion'''.  As with diffusion it occurs from areas of high concentration to those of low so is a '''passive''' process.

Transport proteins allow hydrophillic molecules, which are too large to get through water filled protein channels, to passively cross the membrane.  The molecules bind to protein and then the protein changes shape depositing the molecule at the other side of the membrane.  This transport method is also known as '''Facilitated Diffusion'''.  As with diffusion it occurs from areas of high concentration to those of low so is a '''passive''' process.

===Differances Compared to Diffusion===

===Differences Compared to Diffusion===

* The proteins are very specific to very few molecules

* The proteins are very specific to very few molecules

* The proteins have a maximal rate.  If the concentration of the molecule to be transported is very high the number of proteins is likely to limit the rate.

* The proteins have a maximal rate.  If the concentration of the molecule to be transported is very high the number of proteins is likely to limit the rate.

* Some of the proteins bind a small number of differant molecules.  These molecules will compete for the proteins and will be transported in similar relative quantites to their original concentrations.

* Some of the proteins bind a small number of different molecules.  These molecules will compete for the proteins and will be transported in similar relative quantities to their original concentrations.

==ATPases==

==ATPases==

===Co-Transporters===

===Co-Transporters===

This family of ATPase membrane proteins are involved in [[Active Transport - Physiology#Secondary Active Transport|Secondary Active Transport]].  They bind two molecules and transport them accross the membrane either in the same direction ('''symporter''') or in opposite directions ('''antiporter''').  The [[Active Transport - Physiology#Development of Potential Energy|potential energy]] derived from forcing one molecule across this allows the other cotransported molecule to be transported against its gradient.

This family of ATPase membrane proteins are involved in [[Active Transport - Physiology#Secondary Active Transport|Secondary Active Transport]].  They bind two molecules and transport them accross the membrane either in the same direction ('''symporter''') or in opposite directions ('''antiporter''').  The [[Active Transport - Physiology#Development of Potential Energy|potential energy]] derived from forcing one molecule across this allows the other co-transported molecule to be transported against its gradient.