Anti-parallel beta sheet

There are two types of Beta-sheets: parallel and anti-parallel. Anti-parallel strands run in opposite directions to each other, this means that the hydrogen bonds between the strands that stabilise the structure are straight. They form between the amine group on one amino acid and the carboxyl group on the opposite amino acid strand, this also happens between the NH group on this amino acid and CO group on the other amino acid, so overall there are two hydrogen bonds between the two amino acids.