Question

Opposite charges attract; like charges repel. Like dissolves like. “Stable” means “low energy” and unreactive, while “unstable” means “high energy” and reactive; and all things spontaneously become more stable over time (unless there is an input of energy), and in becoming more stable they release energy. Explain how one or more of those principles apply to each of the following:

Chemical bonds form between atoms: ionic, hydrogen, and covalent. (2.5 points)

Particular proteins always assume particular elements of 3-D shape/secondary structure. (2.5 points)

Answer 1

If the outer shell is filled, the atom is stable. Atoms with unfilled outer shells are unstable, and will usually form chemical bonds with other atoms to achieve stability.
In ionic bonds, atoms donate or receive electrons to achieve stability. In covalent bonds, atoms share electrons to achieve stability.
Hydrogen bonds are formed between an electronegative atom and a hydrogen atom bonded to a second electronegative atom. The formation of hydrogen bonds is important in biological systems because the bonds stabilize and determine the structure and shape of large macromolecules such as nucleic acids and proteins.

Proteins are made up of many amino acids that are bound with one to their next with the peptide bonds. A functional protein will have this polypeptide chain in several folded condition. At every folding, the amino acids of one turn their adjacent turn will again bind with each other by various types of bonds like hydrogen bonds, disulfide bonds etc.
Large numbers of hydrogen bonds that form between adjacent regions of the folded polypeptide chain help stabilize its three-dimensional shape and which in turn provide the structural and functional stability of the polypeptide or protein.