2. In this chapter, you learned that some pathogens must attach to host cells to cause disease. To accomplish this, molecules on their surface (adhesins or ligands) recognize and attach to molecules (receptors or integrins) on the surface on certain host cells.
So a chromatic note, is any note you play that is not in the scale you are playing. They are also a great way to practice, especially if you are going through the pentatonic scale. Try adding one of these outside chromatic notes to your scale, and see how it sounds above the chord you are playing over.
Post #2. it means to add any note from the prevailing scale, So, if you were playing the E pentatonic scale - that is only 5 notes, but the chromatic scale is every note in the scale so providing you chose a note from the E scale, you would be adding a chromatic note whilst mainly playing the pentatonic scale.