E. From A to B; at equilibrium mostly B would be present; the reaction would be slow. A. From A to B; at equilibrium mostly B would be present; insufficient information is given to predict the rate of the reaction. 
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Building a polypeptide: Polymers are chains of subunits, monomers, linked together by chemical bonds. The bond between two amino acids is known as a peptide bond. Two amino acids, joined together by a peptide bond, are known as a dipeptide. An amino acid polymer is known as a polypeptide.
http://virtuallaboratory.colorado.edu/Biofundamentals/lectureNotes/Topic3-4_Peptide%20bonds.htm
D. From the information given, the direction and how far the reaction would proceed cannot be determined; the rate of the reaction would be fast. A. From A to B; at equilibrium mostly B would be present; insufficient information is given to predict the rate of the reaction.
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Proteins are composed of α-amino acids linked together by peptide bonds into polypeptide chains. An amino acid is characterized by an amino group (-NH2) and a carboxylic acid group (-COOH) linked to a carbon, known as the α-carbon. Also attached to the α-carbon is a H and various R-groups or side-chains.
http://virtuallaboratory.colorado.edu/Biofundamentals/lectureNotes/Topic3-4_Peptide%20bonds.htm
The use of a C-terminal protecting group depends on the type of peptide synthesis used ; while liquid-phase peptide synthesis requires protection of the C-terminus of the first amino acid ( C-terminal amino acid ) , solid-phase peptide synthesis does not , because a solid support ( resin ) acts as the protecting group for the only C-terminal amino ...
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Peptide synthesis most often occurs by coupling the carboxyl group of the incoming amino acid to the N-terminus of the growing peptide chain. This C-to-N synthesis is opposite from protein biosynthesis, during which the N-terminus of the incoming amino acid is linked to the C-terminus of the protein chain (N-to-C).
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Introduction to peptide synthesis. Peptide synthesis is characterized as the formation of a peptide bond between two amino acids. While the definition of a peptide is not definitive, it usually refers to flexible (little secondary structure) chains of up to 30-50 amino acids.
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1 A polypeptide is a single linear chain of many amino acids, held together by amide bonds. 2  A protein is one or more polypeptide (more than about 50 amino acids long).  An oligopeptide consists of only a few amino acids (between two and twenty).
https://en.wikipedia.org/wiki/Peptide
Peptides (from Gr.: πεπτός, peptós digested; derived from πέσσειν, péssein to digest) are biologically occurring short chains of amino acid monomers linked by peptide (amide) bonds. The covalent chemical bonds are formed when the carboxyl group of one amino acid reacts with the amine group of another. The shortest peptides are dipeptides, consisting of 2 amino acids joined by a single peptide bond, followed by tripeptides, tetrapeptides, etc. A polypeptide is a long, continuous, and unbranched peptide chain.
https://en.wikipedia.org/wiki/Peptide
This type of approach has a two-fold function: the resin acts as the C-terminal protecting group and provides a rapid method to separate the growing peptide product from the different reaction mixtures during synthesis.
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what type of reaction is used to make a polypeptide chain
The reaction in which a single linear chain of many amino acids, held together by amide bonds is used to make a polypeptide chain.