Aquaporin and Cell Membranes

Interdisciplinary Investigation (IDI)-ClassroomAquaporins

Use MolView to explore a 3D image of a phospholipid (shown below) by entering “phospholipid” into the search window. Under the “Model” menu item you can explore different 3D views of this molecule (Ball and Stick, Stick, etc.). Under “Jmol” menu item you can explore the charges on the molecule by clicking on “MEP surface lucent”. This electrostatic potential diagram uses red to indicate negative charge, blue to indicate positive charge and green for neutral or no charge. After exploring the 3D model complete the following:

1. In box 1 below, describe the intermolecular forces that are present between the polar head groups of adjacent phospholipids.Are hydrogen bonds possible?
2. In box 2, describe the intermolecular forces that are present between the hydrocarbon “tails” of adjacent phospholipids.
3. In box 3, describe possible forces present between a membrane bound protein and the phospholipid. Be sure to describe the forces present between the protein and the polar head group and the forces present between the protein and the hydrocarbon chain.

1. Hydrogen Bonding

1. Use MolView to explore a 3D image of a water molecule by entering “water” into the search window. Under the “Model” menu item you can explore different 3D views of this molecule (Ball and Stick, Stick, etc.). Under “Jmol” menu item you can explore the charges on the molecule by clicking on “MEP surface lucent”. This electrostatic potential diagram uses red to indicate negative charge, blue to indicate positive charge and green for neutral or no charge. After exploring the 3D model complete the following:
2. Draw a single-file line of 5 water molecules in the appropriate orientation and label the intermolecular forces between the water molecules.

1. What are the differences between hydrogen bonds and covalent bonds? Use your line of water molecules you drew above to show where covalent bonds are located and where hydrogen bonds are located.

2. Use MolView to explore a 3D image of the aminoacid Arginine(shown below) by entering the name into the search window. Under the “Model” menu item you can explore different 3D views of this molecule (Ball and Stick, Stick, etc.). Under “Jmol” menu item you can explore the charges on the molecule by clicking on MEP surface lucent. This electrostatic potential diagram uses red to indicate negative charge and blue to indicate positive charge. Notice that the hydrogen atoms bonded to nitrogen are very positive.

1. After exploring the 3D model, determine where water might interact with arginine through hydrogen bonding. Draw these hydrogen bonds in the space below. Be sure to show partial charges on both arginine and water and clearly label each hydrogen bond.

Part 4: Interdisciplinary Drawing Challenge

Challenge:What do you think  the aquaporin water channel through a cell membrane looks like? How would Aquaporin orient itself in the cell membrane? Would such a channel need to be specific for water?  If so, how could it accomplish this specificity?

Part 3: Discussion

Read the two articles posted below. Select one aspect of EACH article that you found particularly interesting and describe what you select.  (Both are attached)

1. “Precious Bodily Fluids”, Pittsburgh Supercomputing Center, 2002
2. The Discovery of Water Channels (Aquaporins) by Dennis Brown, Annuals of Nutrition & Metabolism, 2017