2.+Membranes+and+cell+organelles

I media type="custom" key="26974874" A chicken egg with the shell removed is often used as a model to show how osmosis works – the experiment we did at Federation University, Ballarat, showed how the eggs gain or lose mass depending on the concentration of the solution that they are placed in. It is important to know that the membrane of the egg is not a true biological membrane or plasma membrane. In fact, a chicken egg is a very specialized cell and the membrane is actually composed of keratin fibres – the same protein that makes up human hair, finger nails and rhino horns. Thanks to Andrew Douch for finding this article about chicken egg membranes, with scanning electron micrograph images. Notice in the image above, the egg in 5% saline solution sinks (indicating that the egg contents are more dense than the solution) and the egg in the 10% saline solution floats (indicating that the egg contents are less dense than the solution). This image should give you a clue as to which egg gains water and which egg loses water by osmosis.

In the egg osmosis experiment we used a chicken egg as a model of an animal cell to demonstrate the movement of water across a semi-permeable membrane. We have learned about the different components of the plasma membrane, including the phospholipid bilayer, integral and peripheral proteins, glycoproteins and glycolipids. We know that it is sometimes referred to as a “fluid mosaic” referring to it’s flexible structure of different parts.

Today we are going to test the effect of temperature and solvents on the cell membrane, using cores of raw beetroot. [|Beetroot is brightly coloured due to the presence of betalain] and this coloured pigment can assist us to determine the effect of different temperatures and concentrations of solvents on the cell membrane. When the cell membrane is damaged, the pigment leaks out, so the more damage that occurs, the darker the colour of the medium into which the pigment leaks. Your task is to design and complete an experiment with an aim, hypothesis, list of materials and equipment, method, results, discussion and conclusion. Your variable can be temperature OR concentration of a solvent (ethanol, for example) or detergent. **Cell Membrane Resources:**
 *  [|Investigating the effect of temperature on plant cell membranes] (from the Nuffield Foundation)
 * [|An example of a practical report]
 * [[file:bio-brainstorm/cell_membrane_permeability.pdf|Another practical report]]
 * Cell membranes - a very detailed site with good images

**Digital resources:** media type="custom" key="27163606"media type="custom" key="26975358"media type="custom" key="27163542"media type="custom" key="27163638"
 *  Cells Alive! has some great interactive models to help you to learn about the structure and function of prokaryotic and eukaryotic cells.
 *  “Membrane structure and function” from the Biology Corner.
 *  “A Tour of the Cell” (YouTube) by Bozeman Science
 *  “Cell Membranes” (YouTube) by Bozeman Science
 *  “Transport across cell membranes” (YouTube) by Bozeman Science
 * <span style="background-color: #ffffff; color: #333333; font-family: Georgia,'Times New Roman',Times,serif; font-size: 14.3999996185303px;"> Cell structure and function slideshow
 * <span style="background-color: #ffffff; color: #333333; font-family: Georgia,'Times New Roman',Times,serif; font-size: 14.3999996185303px;"> Cell membrane transport slideshow
 * <span style="background-color: #ffffff; color: #333333; font-family: Georgia,'Times New Roman',Times,serif; font-size: 14.3999996185303px;"> [|Animal cell diagram] to annotate online
 * <span style="background-color: #ffffff; color: #333333; font-family: Georgia,'Times New Roman',Times,serif; font-size: 14.3999996185303px;"> “Apoptosis” (YouTube) – Programmed cell death.

<span style="background-color: #ffffff; color: #333333; font-family: Georgia,'Times New Roman',Times,serif; font-size: 14.3999996185303px;">**Possible Tasks:**
 * 1) <span style="background-color: #ffffff; color: #333333; font-family: Georgia,'Times New Roman',Times,serif; font-size: 14.3999996185303px;">Create a “Thinglink” interactive image, labelling the different parts of a eukaryotic cell.
 * 2) <span style="background-color: #ffffff; color: #333333; font-family: Georgia,'Times New Roman',Times,serif; font-size: 14.3999996185303px;">Create a database of terms and definitions on Quizlet.
 * 3) <span style="background-color: #ffffff; color: #333333; font-family: Georgia,'Times New Roman',Times,serif; font-size: 14.3999996185303px;">Decorate a cake to show the different organelles of a plant or animal cell. Label with toothpick flags.
 * 4) <span style="background-color: #ffffff; color: #333333; font-family: Georgia,'Times New Roman',Times,serif; font-size: 14.3999996185303px;">Create a video describing the different forms of active transport using “common craft” style or 3D animation.
 * 5) <span style="background-color: #ffffff; color: #333333; font-family: Georgia,'Times New Roman',Times,serif; font-size: 14.3999996185303px;">Create a labelled model of the “phospholipid bilayer with integral and peripheral proteins”.