Membranes must be "fluid" to work properly. When a balloon breaks the air escapes from within down its pressure gradient and the balloon is no longer very much fun. Likewise, when a membrane breaks all of the chemicals in and out diffuse down their concentration gradients and the life of the cell is in serious jeopardy.

Fluidity is temperature dependent. Organisms that live in cold climates have different membrane compositions than those that live in warm climates. Organisms that live in variable climates have the capacity to change their membrane compositions. Moving an organism into a climate to which it is not adapted can be bad. For example, if you carry a poinsettia (a common holiday plant from the tropics) to your car in mid winter it will likely turn black and die. The poinsettia's cell membranes "break" at cold temperatures.

Questions: How are membranes from warm and cold adapted organisms different? Why do cold membranes break?

8/22/04 Copyright (C) 2004, Jonathan Monroe, monroejd@jmu.edu. All rights reserved.
URL: http://csm.jmu.edu/biology/courses/bio220/qotw3.html