Final answer:
Parallel β-sheets are stabilized by hydrogen bonds, which occur between the backbone atoms of amino acids in proteins.
Step-by-step explanation:
The parallel β-sheets in the structure of proteins are stabilized by hydrogen bonds. These bonds occur between the carbonyl oxygen of one amino acid and the amide hydrogen of another, which are part of the polypeptide backbone. Hydrogen bonds are much weaker than covalent bonds, but they are crucial for the secondary structure of proteins, including β-sheets, α-helices, and turns.
As for the types of molecular bonds:
- A covalent bond involves the sharing of electron pairs between atoms.
- An ionic bond forms when one atom donates an electron to another atom, resulting in a bond between ions with opposite charges.
- A metallic bond occurs in metals, where electrons are shared and can move freely between the atoms.