Advanced Placement (AP) Biology Practice Exam

Growth factors are essential proteins that play a critical role in regulating cell growth, proliferation, and differentiation. They are typically secreted by cells and act on nearby target cells to promote their development and function. The primary function of growth factors is to stimulate cell proliferation, meaning they encourage cells to divide and multiply, which is vital for tissue growth and repair. Additionally, growth factors can induce differentiation, guiding stem or progenitor cells to develop into specialized cell types that perform specific functions within the body. The significance of growth factors in cellular processes can be seen in various biological contexts, such as during embryonic development, wound healing, and tissue regeneration. By interacting with specific receptors on target cells, growth factors activate signaling pathways that lead to these important cellular responses. The other options present functions that do not align with the primary roles of growth factors. For instance, acting on distant cells to inhibit growth, destroying damaged cells, or harvesting energy are functions that are related to different cellular processes or mechanisms which do not encompass the fundamental action of growth factors in stimulating growth and differentiation.