When using AEC (automatic exposure control) for a PA chest projection, which ionization chamber(s) should be activated?

For a tetrapeptide, there are ____ unique sequences.

Although mutations can change the catalytic efficiency of an enzyme, we are certain that mutations will never alter the ________.

If the Keq of an enzyme-catalyzed reaction is highly favorable, then ________.

For the following amino acid (pK1 = 2.2 (carboxyl); pK2 = 8.6 (amino); pK3 = 10.5 (phenolic hydroxyl), the most abundant form at pH 9 is _______.  

In proteins, R-N–H···O=C-R bonds ________.

An enzyme ________________________________.

A channel protein

Countertransport

A governing system in which public decision making is delegated to representatives of the people chosen by popular vote in free, open, and periodic elections is a(n)