Phosphofructokinase is a four-subunit protein with four active sites. phosphofructokinase catalyzes step 3 of glycolysis, converting fructose-6-phosphate to fructose-1,6-bisphosphate. phosphoenolpyruvate (pep) is the product of step 9 of glycolysis. the pep concentration in the cell affects phosphofructokinase activity. select the true statements about pep regulation of phosphofructokinase. a. pep is a feedback inhibitor of phosphofructokinase. b. the apparent affinity of phosphofructokinase for its substrate increases when pep binds. c. pep is a positive effector of phosphofructokinase. d. pep inhibition of phosphofructokinase yields a sigmoidal velocity versus substrate curve. e. pep competes with fructose-6-phosphate for the active site of phosphofructokinase. f. the binding of pep to one phosphofructokinase subunit causes a conformation change that affects the ability of the substrate to bind to the other subunits.

Three cards with holes are arranged in a straight line. a light is shined through the first card’s hole and travels through all three cards. what does this tell you about light rays? a) that light is reflected b) that light is refractive c) that light travels in a straight line d) that light does not travel in a straight line

Straightforward questions answered in the powerpoint slidesreaction: heating the starting materials under refluxwhat does it mean to heat under reflux? why do we choose water as the reflux solvent? what are boiling chips used for? why do we put a condenser on top of the reaction? why do we add heat and let the reaction stir for 30 minutes? why do we add sulfuric acid to the reaction after it cools as opposed to when it’s still hot? separation: filtration of precipitatewhy don’t we do an aqueous and organic extraction in the separatory funnel? why do you rinse the salicylic acid on the filter with ice cold water? purification: recrystallization of salicylic acid (no hot filtration needed)what is the difference in the amount of room temperature water vs. boiling water needed to dissolve the salicylic acid (assume a 1.2 gram yield of salicylic acid)? remember, in the lab if you need x ml of boiling water to dissolve a solid, then you should add a little more (definitely no more than 1.5 times the theoretical amount) to ensure it doesn’t recrystallize prematurely. analysis: melting point of salicylic acidwhat can you conclude if the melting point of the salicylic acid you just synthesized is 152-155oc and the 1: 1 mix of your product and “synthetic” salicylic acid is 151-154oc?

What is the independent variable in this investigation? mass volume sample number substance density