Before revision:  These proteins are so tightly packed that their excluded area interactions can alter the free energy landscape associated with their conformational degrees of freedom .
After revision:  These proteins are so tightly packed that their excluded area interactions can alter the free energy landscape associated with their conformational degrees of freedom. Despite their obvious importance, crowding phenomena in membranes are much less well studied than in the cytoplasm. Using statistical mechanics results for hard disk liquids, we show that crowding induces an entropic tension in the membrane, which influences transitions that alter the projected area and circumference of a membrane protein .