helix
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Article
7 sectionsContents
- Properties and types
- Handedness
- Mathematical description
- Arc length, curvature and torsion{{anchor|Arc length|Curvature|Torsion}}
- Examples
- See also
- References
thumb|upright=1.35|(l-r) Tension, compression and torsion coil springs thumb|upright|A machine screw thumb|The right-handed helix for with arrowheads showing direction of increasing
A helix (; ) is a shape like a cylindrical coil spring or the thread of a machine screw. It is a type of smooth skew 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 , "twisted, curved". A "filled-in" helix – for example, a "spiral" (helical) ramp – is a surface called a helicoid.