Final answer:
Insulin assists in the uptake of glucose in skeletal muscle fibers, promotes glycogenesis, and stimulates protein synthesis. It does not cause gluconeogenesis or directly make muscle fibers use fats for energy.
Therefore, the effects of insulin in skeletal muscle fibers include causing glycogenesis (B) and increasing protein synthesis (C).
Step-by-step explanation:
The effect of insulin in skeletal muscle fibers includes several physiological processes. Insulin promotes the uptake of glucose by triggering the translocation of Glut-4 transporters to the plasma membrane, which results in increased glucose influx into muscle cells. Once inside these cells, glucose is immediately converted into glucose-6-phosphate. This conversion creates a concentration gradient that facilitates the continuous movement of glucose from the blood into the cells.
Moreover, insulin plays a vital role in stimulating the storage of glucose as glycogen in liver and muscle cells through the process known as glycogenesis. This stored glycogen can be utilized later to meet the energy needs of the body. In addition to its role in glucose metabolism, insulin is crucial in promoting the synthesis of proteins in muscle tissues, such as actin and myosin, which are essential for muscle fiber function and growth.
Therefore, the effects of insulin in skeletal muscle fibers include causing glycogenesis (B) and increasing protein synthesis (C). However, insulin does not cause these fibers to perform gluconeogenesis; rather, it stimulates the storage and usage of glucose. Also, insulin does not directly cause fibers to use fats for energy, although it does influence overall metabolism which can affect how cells utilize various energy sources.