Net positive.
negative
A positive charge
Electrons
depends on the polarity of the membrane
-- They can if the gravitational force of attraction is greater than the electrostatic force of repulsion between them. -- They also can if they're connected by a rubber band that has been stretched. -- But if the only force between them is the electrostatic force due to their charges, then they must always repel, because their charges have the same sign.
Any "object" larger than elementary particles consists of positive and negative charges. If your object has a negative charge, it simply has more particles with a negative charge than particles with a positive charge.
negative
positive
A positive charge
Charge is the measure of extra positive or negative particles an object has.
Electrons
Then the charge of the giving object becomes more positive, and the charge of the receiving object becomes more negative.
That means that the object has more particles with a negative charge than particles with a positive charge (or the other way round).
depends on the polarity of the membrane
If the positive and negative charges are equal, then the object has a 'net' neutral charge.
Positive and negative charges would have not effect on an object without charge.
It gains electrons. The only charged particles which can freely move from one object to another are electrons. Electrons have negative charge. So adding electrons gives a negative charge, and removing electrons gives the object a positive charge.