Question

1. fill in the following chart using what youve learned from models 1 - 3.

structure	bond(s) or interactions holding the structure together	short description	number of polypeptide chains involved
secondary			1
tertiary			1
quaternary			2 or more

Explanation:

1. Primary Structure: The primary structure of a protein is held together by peptide bonds. These are covalent bonds formed between the amino - and carboxyl - groups of adjacent amino acids. It is the linear sequence of amino acids in a polypeptide chain.
2. Secondary Structure: It is stabilized by hydrogen bonds between the backbone atoms of the polypeptide chain. Common secondary structures are alpha - helices and beta - sheets.
3. Tertiary Structure: Tertiary structure is maintained by various interactions including disulfide bonds, hydrogen bonds, ionic bonds, and hydrophobic interactions. It gives the overall 3 - D shape of a single polypeptide chain.
4. Quaternary Structure: When a protein consists of multiple polypeptide chains (subunits), the quaternary structure is held together by non - covalent interactions such as hydrogen bonds, ionic bonds, and hydrophobic interactions between the subunits.

Answer:

Structure	Bond(s) or interactions holding the structure together	Short description	Number of polypeptide chains involved
Secondary	Hydrogen bonds (between backbone atoms)	Local regular structures like alpha - helices and beta - sheets	1
Tertiary	Disulfide bonds, hydrogen bonds, ionic bonds, hydrophobic interactions	Overall 3 - D shape of a single polypeptide	1
Quaternary	Hydrogen bonds, ionic bonds, hydrophobic interactions	Interaction between multiple polypeptide subunits	2 or more