A three dimensional spiral.
All of them. Tertiary is the overall 3D shape of the protein Quaternary is what proteins it is attached to and how Primary is the actual order of the amino-acids which make up the chain Secondary is the way that that chain coils or folds So 'helix' refers to the coiling of the chain. Hence it is the secondary structure.
Double Helix
The supporting structure of the DNA double helix is called the sugar-phosphate backbone.
In the DNA. The term "double helix" refers to the structure of DNA.
Normally, DNA forms a right-handed double helix but it can also come in other forms.
Double Helix the structure of double coiled DNA
The sugar-phosphate supporting structure of the DNA double helix is called the backbone. This is why the DNA is commonly referred to as a double helix.
double helix
It's a double helix.
sheet
helix
It's a double helix.