A Level Biology Practice Exam

What are cytokines primarily involved in?

1. Transporting oxygen in the bloodstream

2. Cell-signaling to recruit phagocytes to infection sites

3. Stimulating muscle contractions

4. Regulating blood sugar levels

The correct answer is: Cell-signaling to recruit phagocytes to infection sites

Cytokines are a group of small signaling proteins released by cells, and they primarily play a crucial role in cell signaling within the immune system. Their primary function is to mediate and regulate immune responses, especially in the recruitment and activation of immune cells such as phagocytes to sites of infection or inflammation. This is essential for fighting off pathogens and advancing the immune response. When an infection occurs, various cells of the immune system release cytokines, which then act on nearby cells to enhance their activity and increase their rate of proliferation or infiltration into the infected area. This process is critical in orchestrating the complex response needed to eliminate the invading microorganisms and facilitate the healing process. The other options pertain to functions that are not related to cytokines. For example, transporting oxygen in the bloodstream is primarily the function of hemoglobin in red blood cells, while stimulating muscle contractions is mainly governed by neurotransmitters and muscle physiology. Regulating blood sugar levels is managed by hormones such as insulin and glucagon. These functions distinctly belong to other biological processes rather than the immune response mediated by cytokines.