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).

(c) The tube and cylinder diagram to the right illus- trates schematically the potassium channel protein from a bacterium. This channel protein consists of four identical polypeptide chains each comprised of 119 residues. The cyan ribbon illustrates only two of the polypeptide chains. The relative positions of 4 α-helices, one from each poly- peptide chain, are shown as cylinders. The red sphere in the central part of the diagram shows the position of a potas- sium ion identified by X-ray structure analysis. A cesium ion (green sphere) was also found to be stabilized in the same position when cesium chloride was introduced into the crys- tals. The cylinders each represent an α-helix running from Tyr62 to Thr74. Considering the position of the potassium ion, in- dicate on one of the cylinders at which end of the cylinder residue Tyr62 is found and at which end residue Thr74 is found. Explain the basis of your answer? Ala23 Thr119 (d) The N- and C-terminal residues of one of the…

2. | Calculate the overall charge (pH 7) on the following three polypeptides and answer the questions below. Assume the following pKa values: N-terminal -NH3®, 7.0; all -COOH groups, 4.0; Arg, 12.5; Cys, 8.4; His, 6.0; Lys, 10.0; Tyr, 10.0. (A) Ser-Tyr-Ser-Met-Glu-His-Phe-Arg-Trp-Gly-Lys-Pro-Val-Gly-Lys-Lys-Arg-Arg-Pro-Val-Lys-Val-Tyr-Pro-Asp-Ala -Gly- Glu-Asp-Gln- Ser-Ala-Glu-Ala-Phe-Pro-Leu-Arg-Glu-Phe (B) Ser-Tyr-Ser-Met-Glu–His-Phe-Arg–Trp–Gly-Ala-Pro-Val-Gly-Glu-Glu-Cys-Asp-Pro-Val-Glu–Val-Tyr-Pro-Asp- Ala-Gly-Glu-Asp-Gln-Ser-Ala-Glu-Ala-Phe-Pro-Leu-Glu-Phe-Cys-Ser-Tyr-Ser-Met-Glu-His-Phe-Asp-Trp-Gly- Asp-Pro-Val-Gly-Pro-Asp-Ala-Gly-Asp-Gln-Pro-Val-Gly-Glu-Glu-Cys-Asp-Pro-Val-Glu-Val-Tyr-Pro-Asp-Ala | (C) Gly-Ser-Val-Arg-Asp-Pro-Val-Lys-Glu–Val-Tyr-Pro-Asp- Lys-Ala-Gly-Arg-Glu-Ser-Arg-Ala (a) Which of the three peptides would elute first from a gel filtration column? (b) Which of the three peptides would migrate the fastest on SDS-PAGE (c) Which of the three peptides could be…

4. A protein solution is prepared by dissolving 350 µg of protein in 200 µL of water. A 150 μL sample of this solution is diluted to a total volume of 4.5 mL. How many mg of protein will be in a 2 mL sample of the diluted protein solution? Space to show your workings:

3. You have a protein that is easily extracted from a cell membrane preparation, without any associated lipids, by washing with a buffer containing a salt (e.g. 2M NaBr) without the need to treat the membrane with detergents. What type of protein do you have? E) Peripheral (extrinsic) F) A protein covalently anchored to membrane fatty acids G) Transmembrane H) None of the above Answer: Explanation: 4. A bacterium is suddenly expelled from a warm human intestine into the cold world outside (hey, it's been a cold December!). Which of the following adjustments might the bacterium make to maintain the same level of membrane fluidity? I) Produce lipids with hydrocarbon tails that are longer and have fewer double bonds Produce lipids with hydrocarbon tails that are shorter and have more double bonds K) Decrease the amount of cholesterol in the membrane L)Decrease the amount of glycolipids in the membrane Answer: Explanation: 5. Which of the following membrane lipids does not contain fatty…

When the potato cube is surrounded by a hypotonic solution what change in mass occurs in the potato cells?

Of the following cell membrane lipids, which one prefers to reside in the inner leaflet (or inner half) of the membrane bilayer, AND has an overall neutral charge at physiological pH (7.4)? a) PE (phosphatidylethanolamine) is inner-leaflet with an overall neutral charge at pH 7.4 b) SM (sphinogomyelin) is inner-leaflet with an overall neutral charge at pH 7.4 c) PS (phosephatidylserine) is inner-leaflet with an overall neutral charge at pH 7.4 d) PC (phosphatidylcholine) is inner-leaflet with an overall neutral charge at pH 7.4

2. | Calculate the overall charge (pH 7) on the following three polypeptides and answer the questions below. Assume the following pKa values: N-terminal –NH3®, 7.0; all -COOH groups, 4.0; Arg, 12.5; Cys, 8.4; His, 6.0; Lys, 10.0; Tyr, 10.0. (A) Ser-Tyr-Ser-Met-Glu-His-Phe-Arg-Trp-Gly-Lys–Pro–Val–Gly–Lys–Lys–Arg-Arg-Pro-Val-Lys–Val-Tyr-Pro-Asp-Ala -Gly- Glu-Asp-GIn– Ser-Ala-Glu-Ala-Phe-Pro-Leu-Arg-Glu-Phe (B) Ser-Tyr-Ser-Met-Glu-His-Phe-Arg-Trp-Gly-Ala-Pro-Val-Gly-Glu-Glu–Cys-Asp-Pro-Val-Glu–Val–Tyr-Pro-Asp- Ala-Gly-Glu-Asp-Gln-Ser-Ala-Glu-Ala-Phe-Pro-Leu-Glu-Phe-Cys-Ser-Tyr-Ser-Met-Glu–His-Phe-Asp-Trp-Gly- Asp-Pro-Val-Gly-Pro-Asp-Ala-Gly-Asp-Gln-Pro-Val–Gly–Glu-Glu-Cys-Asp-Pro–Val-Glu–Val–Tyr-Pro-Asp-Ala (C) Gly-Ser-Val-Arg-Asp-Pro-Val-Lys-Glu-Val-Tyr-Pro-Asp- Lys–Ala-Gly-Arg-Glu-Ser-Arg-Ala (d) Which of the three peptides would migrate the closest to the anode in isoelectric focusing? (e) Which of the above peptides would elute last from a gel filtration column? (f) Which of the three…

20. The dissociation constant of protein Z for ligand Y is: 10 micromolar. What fraction of the ligand is bound at ligand concentration = 5 micromolar?

Explain