There are many applications today that require a nano-scale communication. Nanonetworks are used in accurate treatments inside the human body in which the size of the tool is an important issue. One of the suggestions for communicating in nanoscale networks is molecular communications, where molecules carry messages. Because of the inherent differences between molecular and radio communications, there is no direct use of radio communication models in molecular communications. Since the study of molecular communication systems from the communication engineering point of view is not more than a few years old, most of the models presented are elementary and simple, and far away from real models. Receiver is one of the main parts of a communication systems. In molecular communication systems, receivers are considered spherical. In realistic, there are receptors on the receiver surface that absorb molecules. These receptors are also unable to reabsorb molecules for a while, after they receive one. Therefore, considering the effect of receptors on the receiving function is important. On the other hand, one of the challenges of molecular communication systems is the high bit error rate. Proposed methods to reduce bit error rates should not require complex operations because transmitters and receivers in molecular communication systems are simple and cannot perform complex operations. Thus, in this thesis, we first investigate the effect of two receptors on each other and an optimal distance between the two receptors is obtained to receive the maximum number of molecules. In the next section, by activating a part of the receptors of the receiver, it is observed that bit error rate is reduced without using any inter symbol interference elimination method. This receiver is more similar to realistic receivers and doesn’t need to perform complex operations.The simulation results show that by activating the receptors at an optimum angle the bit error rate reaches its lowest value. Keywords: Molecular Communication, Diffusion, Receiver, Receptor, Inter Symbol Interference