Molecules that cannot cross the membrane bind to receptors in the membrane. When the signal binds to a receptor changes it's shape. Other Molecules inside the cell respond to the chainging shape of the receptor.
Hey there!
The answer to that is genes.
Genes are parts of the DNA and are the functional unit of inheritance.
Genes are the reason why a child looks like his/her parents. Genes from the parents are inherited to the child and are in the child's DNA.
Hope this helps. Have an awesome day! :)
P.S. Congrats on asking the 8 millionth question on Brainly!