Question

1. examine the tertiary structure in model 3 and note the interactions that hold this level of structure in place.

a. four types of bonds or interactions are shown. label them with the following terms:
disulfide bridge
hydrophobic interactions
hydrogen bond
ionic bond
b. describe the part of the amino - acid that participates in these interactions.

1. how many polypeptide chains are shown in the tertiary protein structure in model 3?

1. many proteins, but not all, have a fourth level of structure termed quaternary structure.

a. how many polypeptide chains are shown in the quaternary structure of the protein in model 3?
b. what types of bonds and interactions hold the quaternary structure in place?

Explanation:

16a. Disulfide bridges form between cysteine - containing R - groups. Hydrogen bonds can form between polar R - groups or backbone groups. Hydrophobic interactions involve non - polar R - groups clustering together away from water. Ionic bonds occur between charged R - groups.
16b. The R - groups of amino acids participate in these interactions, with some exceptions like hydrogen bonds which can also involve backbone groups.

1. Without seeing Model 3, in a tertiary protein structure, there is 1 polypeptide chain.

20a. Without seeing Model 3, in a quaternary structure, there are multiple (more than 1) polypeptide chains.
20b. The quaternary structure is held together by hydrogen bonds, hydrophobic interactions, ionic bonds, and sometimes disulfide bridges.

Answer:

16a. Disulfide bridge: between cysteine R - groups; Hydrogen bond: between polar R - groups or backbone; Hydrophobic interactions: non - polar R - groups; Ionic bond: between charged R - groups
16b. R - groups (and backbone for hydrogen bonds)

1. 1

20a. Multiple (more than 1)
20b. Hydrogen bonds, hydrophobic interactions, ionic bonds, disulfide bridges (sometimes)