A certain membrane protein is found on the ER membrane with the N-terminus on the ER side of the membrane and the C-terminus on the cytosol side of the membrane. The protein contains three transmembrane domains. What would be the orientation of the protein across the ER membrane if the gene were mutated such that the third transmembrane domain coded for hydrophilic amino acids? (B) (C) N C =1881- N C ER LUMEN CYTOSOL (A) N Choose one: O Orientation A O Orientation B O Orientation C O Orientation D (D) N rough ER membrane

Consider the peptide Asp-Lys-Phe-Glu-Asn-Tyr-Gln-Val-Cys. In a single beaker, you treat this peptide with 2 proteases. One protease cleaves at the N-terminus of aromatic R groups and the other cleaves at the C-terminus of polar, non-ionizable R groups. Following the enzymatic digestion, you want to separate your peptide fragments so that you can identify them. You choose to separate the fragments using an anion exchange column. Beginning at pH=6 you apply your peptide fragments to the column and you gradually decrease the pH of the column stopping the separation when the pH of the column equals 4. Omitting chemical structures, write the amino acid sequence of the peptide fragments that are produced from this digest. Write the order that these fragments will elute from the column (if at all). (Relevant pKa values are: 2.1, 3.8, 4.3, 8.3, 9.6, 10.1, and 10.5)

In Figure 9-12, is the terminal amino acid emerging fromthe ribosome encoded by the 5′or 3′end of the mRNA?

Transport of histidine into a bacterial cell was measured at several different histidine concentrations, see table below. Based on these data, is histidine uptake facilitated by a carrier or channel protein? a b Histidine (uM) 2.5 7 16 31 72 с Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. A carrier protein because it becomes saturated. A carrier protein because it does not become saturated. A channel protein because it becomes saturated. Transport (uM/min) d A channel protein because it does not become saturated. 42.5 119 240 490 1000 X Your answer