Which protein function involves helping transport substances within the body?

The function involving helping transport substances within the body is indeed related to transportation. Protein molecules play crucial roles in moving various substances throughout the body, including nutrients, hormones, and waste products. Specific transport proteins, such as hemoglobin, carry oxygen in the blood, while others transport other critical molecules, such as glucose or lipids, across cell membranes.

This transportation function is vital for maintaining homeostasis, ensuring that cells receive the necessary compounds to operate efficiently and effectively. Without these transport proteins, essential elements would not reach their destinations, leading to various physiological issues.

The other options, while important functions of proteins, do not primarily focus on the transport aspect. Acid-base balance involves maintaining pH levels in the body, fluid regulation is about managing the distribution and balance of water, and the immune response is related to defending the body against pathogens.