Tuesday, February 1, 2011

I'm about to diffuse the situation...

AAAAHHHHH!!! You just had an action potential.The concept of membrane transport is one of the fundamental concepts of cell biology, and is the foundation for human physiology. Our cells are responsible for setting up and maintaining the concentration gradients of ions and molecules, which in turn provide the resting membrane potential that is essentially a charge differential from the inside of a cell, to the outside. All of this is done while maintaining osmotic equilibrium. So, how do all of these molecules and ions pass through the phospholipid bi-layer? There are several different mechanisms for transport, that can be broken up into active processes, and passive processes. The active processes require some sort of cellular energy (i.e. ATP), and move substances against their concentration gradients, while the passive processes move substances along the concentration gradient, and do not require the input of energy.

Passive transport can be further subdivided into simple diffusion, osmosis, facilitated diffusion, and filtration. Simple diffusion is the passing of substances through the lipid bi layer along the concentration gradient without the use of a membrane protein. Facilitated diffusion differs in that a trans-membrane protein acts to "carry" the substance through the lipid bi layer via conformational changes protein. Osmosis is the movement of water through fluid filled channels, or aquaporins from an area of lower relative solute concentration to an area of higher solute concentration, until osmotic equilibrium is reached, where the relative concentration of solutes is equal on each side of the membrane. Filtration  makes use of a pressure gradient, which acts to allow for selective passage by allowing only some particles through the channel. This especially useful in organs like the kidneys, which are responsible for filtering waste from our bodies.

Active transport is the movement of a substance against the concentration gradient, and makes use of specific transport proteins. Active transport may be primary, as with the sodium-potassium-ATPase "pump", of secondary, like the SGLT transporter, which relies on the energy created by diffusion of sodium to allow the passage of glucose as sort of a hitchhiker.

Both of these types of transport combine to provide antagonistic, and cooperative effects that are essential to sustaining life. One must remember, that sometimes the smallest things are responsible for the most amazing processes.

In this blog, I attempted to "arouse and fulfil" by using a creative subject heading, and first line. I wanted to try to also speak to a more broad audience by eliminating a great deal of jargon, while still explaining an important concept. Lastly, I attempted to read my writing aloud, which when I was working in the lab didn't make me look the most sane, but I digress.


  1. I really enjoyed your post. The title and hook were enough for me to keep reading. I think you presented an important topic in science without using to much jargon.

  2. I like the style as well. Nice and casual, and a quick summary of the topic. The one thing that would be a good addition is an example. You mention the kidneys, which is great, but a specific example could bring these concepts to life.