Are covalent bonds strong?
Covalent bonds are the strongest of all bonds involving organic compounds. The hydrogen bonds help keep the tertiary structure together, but typically the more covalent (and hydrogen) bonds that a structure has, the harder it is to break up the molecule. Sulfide bonds are very strong, they are in DNA, RNA, amino acids, and plenty other compounds that make up the entire body. Cysteine and Methionine are the amino acids that have sulfide, and when they form those bonds, they amino acids (or protein eventually) usually has a structural role, but not always. Hope this helps.
