Unit Two
Day 17: Biopolymers and Biomolecules
As you work through the modules, if you find that you need a bit more background material to help you understand the topics at hand, you can consult “Chemistry: The Molecular Science” (5th ed. Moore and Stanitski) Chapter 10-5c, 10-7, and Chapter 7-7.
Complete all of these tutorial modules:
Watch this video showing denaturation of egg-albumin protein by a heavy metal, acid, and high temperature.
Exercise 1: Biopolymers
Exercise 2: Forces within DNA Strands
Exercise 3: Forces within DNA Molecules
Podia Question
The presence of per- and polyfluoroalkyl substances (PFASs) in the environment is a significant public health issue. Some sites in Wisconsin, many in Michigan and other states have been identified as being contaminated by these compounds. They’ve been dubbed “forever chemicals” because they don’t degrade naturally. See the Science article at this link for more information. The Science article says that one of the problems of PFASs is the strength of the C–F bond, “Sunlight can’t break it. Water can’t break it.” Another problem is the fact that some of the molecules involved have structures that enable water and airborne droplets to carry them long distances away from their sources.
1. One of the PFASs is perfluorooctanoic acid, which is used in the manufacture of teflon polymers. (Perfluoro means that all H atoms in a hydrocarbon chain have been replaced by F atoms.) Write a Lewis structure for perfluorooctanoic acid.
2. Let’s explore “Sunlight can’t break it.” Describe what needs to happen for sunlight to break a chemical bond. Do a calculation to show whether sunlight that reaches the surface of the Earth could break a C–F bond. (According to NASA, “little to no radiation below 290 nm reaches the Earth’s surface”. )
3. Let’s explore “Water can’t break it.” Hydrolysis is a reaction in which water breaks a chemical bond. Consider hydrolysis of one C–F bond in perfluorooctanoic acid to replace one F atom with an OH group and form HF. Do a calculation to show that water can’t hydrolyze the C–F bond.
4. Consider the structure of perfluorooctanoic acid and the statement above that “some of the molecules involved have structures that enable water and airborne droplets to carry them long distances.” Use scientifically appropriate language to explain why this statement is correct.
5. Other perfluoroalkyl substances have longer chains of carbon atoms than perfluorooctanoic acid. In what type of body tissue would you expect to find these substances? Explain.
Two days before the next whole-class session, this Podia question will become live on Podia, where you can submit your answer.
