Cell membranes are selectively permeable, regulating which substances can pass through, as well as how much of each substance can enter or exit at a given time. in cells, some molecules can move down their concentration gradients by crossing the phospholipid portion of the membrane directly, while others must pass through membrane proteins. which of these statements does not apply to facilitated diffusion?

You are studying several alleles of an e. coli helicase gene. one allele, called rsr, confers resistance to rs2014, an antibiotic that works by inhibiting helicase activity. bacteria with the rss allele are sensitive to rs2014. another allele, called ts-, produces a temperature sensitive mutation of the helicase. in bacteria with the ts- allele, helicase is inactivated at 42 °c but functions normally at 37 °c. helicase functions normally at both temperatures in bacteria with the ts allele. you obtain the following data while testing four strains of e. coli at different temperatures and doses of rs2014. each number represents the percentage of maximal dna synthesis. based on this data, assign the appropriate genotype to strains a–d in the spaces provided