P3D v4 PBR Material Question

I am working on incorporating PBR materials on my project. I am now able to assign materials in Max and see them in sim. I am trying to understand what I need to do with my existing textures. I assign my diffuse texture in the albedo slot and it shows, but the alpha layer no longer seems to have an effect. What needs to be done with an existing diffuse texture to make it usable in a PBR material?
 
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