4. Which of the three major types of membrane receptors is often used by bacteria to cause infections?

on channel-linked receptors, G-protein-linked receptors, and enzyme-linked receptors.

The ability of cells to communicate through chemical signals originated in single cells and was essential for the evolution of multicellular organisms. In multicellular organisms, cells send and receive chemical messages constantly to coordinate the actions of distant organs, tissues, and cells. Cells can receive a message, transfer the information across the plasma membrane, and then produce changes within the cell in response to the message. Single-celled organisms, like yeast and bacteria, communicate with each other to aid in mating and coordination. Cellular communication has developed as a means to communicate with the environment, produce biological changes, and, if necessary, ensure survival.

b is dominant over the allele for the white fur.

i believe the answer would be b. hope it : )