Determine whether each term describes the primary, secondary, or tertiary structure of proteins (or forces relating to the primary, secondary, or tertiary structure of proteins).

1. salt bridge

2. amide bond

3. disulfide bond

4. beta-pleated sheet

5. alpha helix

1. salt bridge - tertiary structure

2. amide bond - primary structure

3. disulfide bond - tertiary structure

4. beta-pleated sheet - secondary structure

5. alpha helix - secondary structure

Explanation:

A salt bridge is simply a neutralisation reaction between two molecules of opposite charge. Examples are: carboxylate ion end (RCOO-) of either aspartic acid or glutamic acid and ammonium ion end (RNH3+) from lysine or guanidinium (RNHC (NH2) 2+) of arginine. The disulfide bond is usually gound in the Cysteine amino acid with the structure R-S-S-R′. Also, it is usually derived by the bonding of two thiol groups. They are both important components of protein and they determine the overall structure of protein and hence its fold.

For beta-pleated and alpha-helix structures, they are usually defined by the varying patterns of hydrogen bonds between the amine - (-NH2) and carboxyl - (-COOH) groups which are at the side chain of the amino acids. They determine the geometry of the protein hence why they are secondary structures.

Amide bond is an unbranched sequence of amide (peptide) bonds which form long chains of polypeptides (polyamides). This shows that it is a primary structure. They are also formed by dehydration where the amine - (-NH2) and carboxyl - (-COOH) groups bonds together to form a peptide bond with the loss of water.