Answering this question for me will be difficult but I will give it a shot.

the answer in a word is yes.

To give better insight, I will do my best.
Let us pretend that you are trying to accelerate your automobile and then decided to drag your foot on the ground while you do so. your automobile most likely will not be able to 'see' the added load being apposed to your action but you know that you are causing a hinderence against the accelleration.

This would be more noticeable if you were on a bicycle where the overall power is much less.

The way we power models anymore you will probably not notice the difference (like the foot and the car example) but the effect will be an increased load on the motor causing more heat and an increase in the amount of amp draw. This will show itself mostly in overall energy consumption more than anything.

As for the weight of the prop, this is most minimal however the prop pitch can make a larger difference.
On the other hand if you had just enough of everything to barely fly the model, you could introduce enough load that the RPMS would not be enough (due to the increased load on the system) to keep the airspeed below stall speed, thus no flying.

I mentioned system. This much is true. Sometimes you can over come a disadvantage by giving the motor more juice. Adding another cell can get you over the hump, provided the motor is not compromised by doing so.
Either way there will be increased power consumption from any increased load you impose on the system (battery ESC motor).

Robert

Alan there were no problem.   I was just wondering about some props are heaver than the APC I've been using, I know that more load req. more AMPs
I guess I was just thinking -(must be having to much time) !!!!