The potential below is a hemogoblin, It has four subunits - each shown in a different color. Each subunit has an Fe atom that binds oxygen for transport around the body. Why would a protein with quaternary structure be better for this task than a protein having only tertiary structure?

(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…

The molecule that condensed with a phosphate group to form the head group of the lipid shown in the first image (picture 6) is choline, an essential component of many cellular molecules.          (a) Draw the structure of choline and explain why it needs a transport protein in order to enter cells.          (b) Cells must transport choline from outside the cell (where it is relatively rare) to the inside of the cell (where it is relatively abundant). The diagram below represents a cell with a choline transporter (labeled T). Draw a solid arrow through the transporter to show the direction in which choline travels (into or out of the cell).           (c) Is T an active or passive transport protein for choline?             (d) For every choline molecule that moves through T, a sodium ion moves through the same transport protein at the same time. The sodium ion moves down its gradient. Add a dashed arrow to the diagram in part (b) to show the direction of movement of sodium.          (e)…

Suppose you have a solution of a protein, which contains a specific Tyr residue that has an actual (measured) pKa of 8.8. The protein binds a ligand by several noncovalent interactions, one of which is a hydrogen bond in which the Tyr phenolic hydroxyl group must serve as a hydrogen bond donor. Calculate the percentage of the protein molecules in which that tyrosyl residue's phenolic hydroxyl group could serve as a hydrogen bond donor at pH 8.5