Question

1. the first five amino acids in this polypeptide are serine, tyrosine, alanine, phenylalanine, and valine, in that order (ser - tyr - ala - phe - val). if the amino acids were changed or rearranged (i.e., to val - phe - ala - ser - tyr), the polypeptide would have a different name and identity. with your group, use this information to write a definition of the primary structure of a protein.
2. locate the secondary protein structure in model 2.

a. what types of bonds are holding the secondary structure in place?
b. what groups on the amino acids are always involved in these bonds?

1. draw a rectangle around two different r groups on the amino acids in the secondary structure in model 2.
2. is there any interaction between r groups in the secondary structure in model 2?
3. secondary protein structure can take the form of an alpha(α)-helix or a beta(β)-pleated sheet, as illustrated below.

a. which drawing represents an α - helix, molecule 1 or molecule 2? explain your reasoning.
b. which drawing represents a β - pleated sheet? explain your reasoning.

1. write a grammatically correct sentence that summarizes how the secondary protein structure is formed from the primary structure.

Explanation:

1. The primary structure of a protein is the linear sequence of amino - acids in a polypeptide chain. Changing or rearranging this sequence changes the protein's identity.

11a. Hydrogen bonds hold the secondary protein structure in place.
11b. The amino (-NH₂) and carboxyl (-COOH) groups on the amino - acids are involved in these hydrogen bonds.

1. (This requires a visual action of drawing a rectangle around two different R - groups on the amino - acids in the given secondary structure model, which cannot be shown in text).
2. No, there is no interaction between R - groups in the secondary structure. Secondary structure is stabilized by hydrogen bonds between backbone atoms, not R - groups.

14a. Molecule 2 represents an α - helix. The α - helix is a coiled structure, and Molecule 2 shows a coiled arrangement of amino - acids with hydrogen bonds stabilizing the coil.
14b. Molecule 1 represents a β - pleated sheet. It has a more extended, sheet - like structure with hydrogen bonds between parallel or antiparallel strands.

1. The secondary protein structure is formed when the primary sequence of amino - acids in a polypeptide chain undergoes folding due to hydrogen bonding between the backbone amino and carboxyl groups.

Answer:

1. The primary structure of a protein is the linear sequence of amino - acids in a polypeptide chain.

11a. Hydrogen bonds.
11b. Amino (-NH₂) and carboxyl (-COOH) groups.

1. (Drawing not possible in text).
2. No.

14a. Molecule 2; because it shows a coiled structure with hydrogen - bonded coil.
14b. Molecule 1; because it has a sheet - like structure with hydrogen - bonded strands.

1. The secondary protein structure is formed when the primary sequence of amino - acids in a polypeptide chain undergoes folding due to hydrogen bonding between the backbone amino and carboxyl groups.