Hi Shahd – thanks for your question.
To answer this – can you provide some context as to where you saw the term positive inhibition? The MCAT requires knowledge on the 4 types of inhibition: competitive, non-competitive, uncompetitive and mixed. If you are referring to the ‘positive’ effects of uncompetitive inhibition on enzyme affinity, this can be understood by the fact that the inhibitor binds selectively to the enzyme-substrate (ES) complex. As inhibitors bind the enzyme-substrate complex, the amount of uninhibited enzyme-substrate complex decreases. This decrease in enzyme-substrate complex causes an increase in the affinity (reflected as a decrease in Km) between the substrate and the enzyme as they now need to replenish the lost enzyme-substrate complex.
Not related to inhibitors – it is possible to have regulatory molecules that bind to a site other than the active site and exert a positive effect on the activity of an enzyme. These are ‘activators’.
The most common application of the salt bridge is in Galvanic cells which contains two half-cells with an electrolyte connected by a salt bridge. A salt bridge contains an inert electrolyte (like potassium sulfate or potassium chloride) whose ions will diffuse into the separate half-cells to balance the building charges at the electrodes. Anions from the salt bridge (eg. Cl-) will flow towards the anode to alleviate the buildup of positive charge. To prevent the buildup of negative charge, cations from the salt bridge flow to the cathode.
Most enzymes with the name dehydrogenase are in the class of enzymes known as oxidoreductases which catalyze oxidation reduction reactions. Dehydrogenases function to oxidize oxidizes a substrate by reducing an electron acceptor, usually NAD+/NADP by transferring hydrogen. For example, lactate dehydrogenase catalyzes the reaction between lactate + NAD <- -> pyruvate + NADH