I should have said turbofan. However the turbine blades are not that much differant. Differant blade airfoil and pitch, and differant materail to take the extra heat. Same concept as a fan or prop in reverse.

Also turnines are not more efficient at altitude. The efficiency actually drops at altitude. The comperssor stage is made so that if given full power it is able to over compress with a very lean mixture, that is much more air than an ideal mixture. A piston engine would knock and overheat with such a lean mixture. As the altitude increase more jet fuel can be added to keep the power at or near the same level. So they are burning more fuel. However the plane is moving in thin air so that it is moving faster which overcompensates for the higer fuel flow. Thus turbine powered planes get better fuel milage at altitude, not because the engines are more efficient but because they slip through the air better. High performance supercharged piston engine aircraft have the same gain at altitude. This was first used to great effect to increase the range of piston powered B-29 aircraft to bomb Japan from distant islands. Jets just get better benifit by being able to climb faster and higher.

BTW another reason many full scale aircraft add more prop blades is to get a better bite in thin air. In fact I think that is the reason the C130 went to six blades. Better performance at altitude.