Final answer:
The membrane potential will become more positive because less potassium will exit the cell, reducing the negativity of the membrane potential when K conductance decreases.
Step-by-step explanation:
If the K conductance decreases in a cell with a typical ECF and ICF membrane potential of -75mV, the membrane potential will become more positive. This occurs because with lower potassium conductance, less K+ will leave the cell, leading to an accumulation of positive charges within it, thus reducing the negativity of the membrane potential.
The resting membrane potential, commonly around -70mV, is established by the selective permeability of the cell membrane and the action of the sodium-potassium pump. The movement of K+ out of the cell via leakage channels is one of the factors that contribute to the resting membrane potential. A decrease in K+ conductance implies that these channels become less permeable to potassium ions, thus not as many positive charges exit the cell, causing the membrane potential to move towards a less negative value.