What is the function of the structure identified by the red arrow? Mobility
Protection
Reproduction
DNA transfer

I'm not entirely sure, however, since no one has answered your question yet, I'll say A. Mobility

This thing probably moves around, and it doesn't look like it could protect it, or anything.

the most logical answer would be a

the solute can move "downhill," from regions of higher to lower concentration, relying on the specificity of the protein carrier to pass through the membrane. this process is called passive transport or facilitated diffusion, and does not require energy.