A-helices are sometimes referred to as "local structures", while b-sheets are usually not local structures. explain. do all proteins contain both a-helices and b-sheets

It is maybe because the alpha helixsecundary structure) characterized by intramolecular hydrogen bonds between amino acid residues and on the other hand,  the beta sheet is composed of extended chains with hydrogen bonds between adjacent chains (between residues from two distinct strands).

Many proteins contain both alpha helices and beta sheets, but some contain just one type of secondary structure.

the most common energy conversion is from kinetic energy to potential energy, and then from potential energy to kinetic energy.

later on comes the heat energy, mechanical energy, and other energy conversions.

this energy conversion is so common that we can find it in our day to day lives as well.

- one of the most common energy conversions involves the changing of potential energy to kinetic energy or kinetic energy to potential energy