A50-ml crude extract of skeletal muscle contains 32 mg of protein per ml. ten μl of the extract catalyzes a reaction at a rate of 0.14 μmol product formed per minute. the extract was fractionated by ammonium sulfate precipitation, and the fraction precipitating between 20% and 40% saturation was redissolved in10 ml. this solution contains 50 mg/ml protein. ten μl of this purifi ed fraction catalyzes the reaction at a rate of 0.65 μmol/min. (a) what is the degree of purifi cation (fold purifi cation)? (b) what is the percent yield of the enzyme recovered in the purifi ed fraction?

Which is an advantage of having memory cells when a pathogen is encountered for a second time. a) the memory cells are what proliferate into clones of cells in response to the binding of an antigen. b) memory cells are vital to the primary immune response in that they immediately recognize pathogens even at the first encounter. c) memory cells are essentially effector cells that are short lived and attack antigens even without having a receptor specific to that antigen. d) it ensures that more lymphocytes with a receptor specific to a particular antigen will be present than in a host that had never encountered that pathogen.