What's the difference between a dendritic cell and a macrophage? Is that a distinction we need to know? And if I explain the body's response to an antigen with a "dendritic cell", but the written answer says "macrophage", do I lose the mark or is the distinction not an issue?
Not really a distinction you have to know in VCE Biology. Dendritic cell should only be used when you're talking about presentation of antigens to T-helper cells. If the question is about the phagocytic removal of dead bacteria etc then you should use macrophages
EDIT: just to add some post-VCE knowledge.
The purpose of dendritic cells is to sample the environment. They phagocytose stuff all around the joint, and then they take little bits of what they've broken down and place it on MHC-II molecules. If they pick up a bacterial antigen, for example, they'll cruise along to the lymph node and show this to the helper T-cells there.
Macrophages, on the other hand, do all the grunt work. They just eat for a living, breaking down all of the dead shit and bacteria around.
So as above, when phagocytosis is the point you're making, talk about macrophages. Dendritic cells have only just started to appear in the course, and they're only really ever talked about when we talk about presentation to T-cells.
It may be able to travel through facilitated diffusion, which is passive. It won't be able to travel via simple diffusion though.
Yeah you can.
Theoretically they can, but they don't. Typically water soluble hormones are large proteins, so they're too big for carrier proteins or channels. They exit by exocytosis normally.