October 11, 2010
Chapter 6.1, 6.2, 6.3 – Online Activities
Online Activity 6.2-Membranes Organize a Cell’s Activity
Dissect a Plasma Membrane
Objective: to understand the structure of a membrane
1. Why is the membrane described as a phospholipid bilayer? It is described as a phospholipid bilayer because there are two layers of phospholipid molecules. 2. How does the arrangement of the phospholipids form a bilayer? The phospholipids arranged in two layers so that the charged phosphate heads interact with the water on either side of the membrane, and the lipid-like (hydrophobic) tails point away from the water and toward each other. 3. In Chapter 4 you learned that water is polar molecule. How does this polarity influence the way in which the phospholipids are arranged in the membrane? The phospholipid molecules have a negatively charged head region that is attracted to the positively charged region of the water molecule. As a result, the hydrophobic nonpolar tail regions are oriented away from the water, forming the interior of the membrane.
Online Activity 6.3-Membranes regulate the traffic of molecules Investigate movement across the membrane.
Objective: To investigate the properties of phospholipids in a cellular membrane
1. What properties of carbon dioxide and oxygen allow them to easily cross a membrane? Carbon dioxide and oxygen both easily cross a membrane because they are both nonpolar, small molecules. 2. What property of the sodium ion prevents it from crossing a membrane? Sodium ion is a charged particile, which prevents it from crossing the hydrophobic region 3. What properties of glucose prevent it from easily crossing a membrane? A glucose molecule is both large and polar, and rarely crosses a membrane by simple diffusion. 4. A benzene molecule is completely nonpolar and a little smaller than glucose molecule. Would it cross a membrane faster, or slower, than glucose? Why? Faster; a...