You are attempting to document the structures of a newly discovered type of protein in your lab. you take them out of storage and allow them to heat up to 37 c. you notice 4 polypeptide chains, each coiled into a 3-d structure. what level of structure are the proteins in?
a. secondary
b. primary
c. quaternary
d. tertiary

D. Tertiary

Explanation:

Polypeptide chains with 3D structure represents tertiary structure of proteins. side chain interacts to form tertiary structure or the side chain interaction with the polypeptide backbone result in the formation of tertiary structure. Four weak forces contribute to make the tertiary structure stable. Hydrophobic interaction plays a key role in this structure, chain contains both resides; hydrophobic as well as hydrophilic too. More hydrophobic residues in the polypeptide chain of protein let the protein to be surrounded by more neighboring parts. Other forces include ionic bonds, hydrogen bonds, and Van der Waals forces, all these forces make interaction that impact in stability of protein structure.

Option A, secondary

Explanation:

The secondary structure of protein comprised of polypeptide chains folded into 3-D  structure. A secondary structure has two types of bond between the polypeptide units of protein -

a) alpha bond - H- bonding in the polypeptide chain that gives it a coiled spring shape

b) beta bond - H- bonding in the polypeptide chain that gives it a folded or pleated structure.

Hence, option A is correct

answer; both surfaces of the membrane are nonpermeable