Posts Tagged ‘diffusion’

Diffusion and osmosis

Wednesday, March 2nd, 2011

YouTube Preview ImageEver wondered how substances move into cells, or why, when you open the front door, you can smell your favourite food cooking in the kitchen, several rooms away?  The answer is diffusion.  We’ll talk about concentration gradients to explain how smells (the nice and the not so nice!) travel through the air.  Here is a useful animation to help you understand the process.

Osmosis is a form of diffusion that deals specifically with water.  Here is a good animation to explain what is going on.  This site goes into some detail about how osmosis affects living organisms and introduces some new vocabulary – hypotonic, hypertonic and isotonic.  Make sure you know what these terms mean.  Can you explain the science behind what is happening in the video above?

Membrane structure

Friday, September 3rd, 2010

Lipid bilayer of the cell membrane - model by wellcome images

We’ll use this presentation in class.  You’ll need to be able to:

  • Draw and label a diagram to show the fluid mosaic model of membrane structure.
  • Explain the terms hydrophobic and hydrophilic, and how these properties help to maintain membrane structure.
  • List the many functions of membrane proteins.

And for a good idea of where this is taking us, here’s a short video.

Cell membrane structure

Monday, November 16th, 2009
Simple diffusion in cell membrane from wikimedia commons

Simple diffusion in cell membrane from wikimedia commons

Some questions to tackle this week:-

  • Do you know what a phospholipid is? 
  • Can you draw a labelled diagram of a cell membrane?
  • What other structures are present in the membrane to help it perform its function of allowing substances into and out of cells?
  • How does this relate to diffusion?
  • Can you explain why the membrane is described as fluid?

Here are some links to images and animations that might help you understand the answers to these questions.

Simple diagram of cell membrane.  More complex diagram of cell membrane.

Animation showing that the cell membrane is selectively permeable by only allowing molecules that are small enough to pass across.

This animation shows how protein channels can help diffusion of larger molecules across the membrane.

This interactive animation explains diffusion and how it relates to membrane structure.