Helix

This article is about the shape. For the shape of deoxyribonucleic acid, see Double helix. For other uses, see Helix (disambiguation).
(l-r) Tension, compression and torsion coil springs
A machine screw
The right-handed helix (cos t, sin t, t) for 0 ≤ t ≤ 4π with arrowheads showing direction of increasing t

A helix (/ˈhiːlɪks/; pl. helices) is a shape like a cylindrical coil spring or the thread of a machine screw. It is a type of smooth space curve with tangent lines at a constant angle to a fixed axis. Helices are important in biology, as the DNA molecule is formed as two intertwined helices, and many proteins have helical substructures, known as alpha helices. The word helix comes from the Greek word ἕλιξ, "twisted, curved".[1] A "filled-in" helix – for example, a "spiral" (helical) ramp – is a surface called a helicoid.[2]

  1. ^ ἕλιξ Archived 2012-10-16 at the Wayback Machine, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus
  2. ^ Weisstein, Eric W. "Helicoid". MathWorld.