Inactive Tutor answered • 04/10/19
Hello,
All the instructions about the structure (size, shape) and functions of the cells are contained within the DNA. The DNA is a molecule in the nucleus of most cells that functions as a blueprint. The DNA molecule can be functionally divided into small segments known as genes. Each gene contains the instructions for the synthesis (manufacture) of a different protein. These instructions are transmitted in the form of RNA from the nucleus into the cells’ cytoplasm. In the cytoplasm, the ribosomes “read” the information that the RNA carries and make proteins following those instructions.
Now, the genes can be turned on or off depending on the type of cell. For example, in a pancreatic Beta-cell, the gene responsible for making insulin is on while the one in charge of making glucagon is off. This same principle applies to the genes that determine how the cytoskeleton develops, how much and when the cells grow, and the number of proteins that they make. All of this is done in coordination with the nervous, endocrine, and immune systems. One example of this is the production of hormones in the thyroid gland. For this gland to make hormones (turn genes on), it has to receive instructions from the pituitary gland, and the pituitary from the hypothalamus that is part of the brain.
Summarizing, what determines the size and shape of the cells is a combination of the actions of the nervous, endocrine, immune systems and the genetic information contained in the DNA of the cells.
Hope this helps!
Regards,
Juan
