Question

Members of a second class of signal molecules are called ___ because they stimulate cell growth and an increase in cell mass.

a. survival factors
b. mitogens
c. growth factors
d. growth hormones

Answer 1

Members of a second class of signal molecules that stimulate cell growth and an increase in cell mass are called growth factors, which bind to cell-surface receptors and initiate signaling pathways for cell division.

Step-by-step explanation:

The members of a second class of signal molecules responsible for stimulating cell growth and an increase in cell mass are known as growth factors. Cells typically do not divide unless they receive such signals from other cells. Growth factors bind to cell-surface receptors, which are often linked to tyrosine kinases, initiating signaling pathways that drive cell division. Oncogenes may produce hormones or mitogens, while proto-oncogenes may encode cell-surface receptors for growth factors, further influencing the cell cycle and division process. Tumor suppressor genes are another class that sends stop signals to regulate cell cycle progression, thereby preventing unchecked cell growth and division.