7. In a chemical reaction, which event ALWAYS occurs as the reaction proceeds?
a. the rearrangement of electrons to break or form chemical bonds
b. the release of energy to the environment
c. the absorption of energy from the environment
d. a change in total mass

Six amino acids have side chains that are polar but not charged. these are serine (ser), threonine (thr), cysteine (cys), asparagine (asn), glutamine (gln), and tyrosine (tyr). these amino acids are usually found at the surface of proteins, as discussed in the proteins 2 module.

Endoplasmic reticulum i believe