10. Which of the following statements is FALSE about proteins? A) The sequence of the atoms in the polypeptide backbone does not vary between different proteins. BYProteins would fold to the most stable conformation with the lowest energy level. C) Misfolded protein can be sent to the proteosome where they will be folded into the correct conformation. DYThe three-dimensional structure of a protein is in general determined by the sequence of the amino acids. E) Proteins are linear polymers built of amino acids.

6. A control phospholipid membrane is isolated in which the phospholipid tails all have an 18-C chain length and are comprised of a 50:50 mixture of saturated and unsaturated tails. In addition, about 25% of the lipids are fluorescently labeled on the head groups. a) Draw a single plot of Fluidity vs. Temperature that contains the expected curves for: Control phospholipid (line- -) Control supplemented with 18-C saturated phospholipids (dashed line - Control supplemented with 16-C chain length (dotted line • • • • • • ) b) Draw a single plot of the Fluorescence Intensity vs. Time that contains the expected curves of a Fluorescence Recovery After Photobleaching (FRAP) using the same samples as in (a) above. The FRAP experiment is conducted at the same temperature for each sample (which is the Tm of the of the control phospholipid).

17. Protein folding results in a large decrease in entropy since a polypeptide is now constrained and more ordered. However, what counterbalances the loss of entropy associated with protein folding?

1. Theoretically, a protein could assume a virtually infinite number of configurations and conformations. Suggestseveral features of proteins that drastically limit the actual number.    2. What are the greatest structural features that differentiate sphingolipids from phosphoglycerides?   3. High levels of glucose-6-phosphate inhibit glycolysis. If the concentration of glucose-6-phosphate decreases,activity is restored. Why?