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A transmembrane protein (TP) is a type of integral membrane protein that crosses the cell membrane in its whole.Transmembrane proteins are found in thecell-to-environment interface, mediating signal transduction and conducting various important cellular biological functions.

The alpha helix and the beta-barrel structures are secondary structures found in transmembrane proteins.Hydrophobic amino acid residues and small amounts of hydrophilic residues, such as charged and polar residues, make up these secondary structures.

Alpha helix referred to a single chain of amino acids coiled into a structural arrangement and held together by hydrogen bonds in many proteins. On the other hand, a beta-barrel is a closed toroidal structure made of a beta-sheet with tandem repetitions that twists and coil, with the initial strand attached to the last strand.

Hence, alpha helix and beta-barrel are two types of secondary structures found in transmembrane proteins.