Which of these cell junctions form a barrier to the passage of materials?

desmosomes (anchoring junctions)
tight junctions
keratin fibers
plasmodesmata
gap (communicating) junctions

True or false: (a) the strings of little red dots represent carbohydrates. (b) the model is called a bilayer because there are two main types of molecules present, lipids and proteins. (c) the many black lines represent amino acid tails. (d) this model shows membrane transport. (e) the blue ovals are hydrophobic. (f) the blue ovals represent phospholipid heads.