Editing Structure (section)

== Biological ==
[[File:Helianthus_whorl.jpg | thumb | right | The spiral arrangement of small bright yellow [[floret]]s that make up the [[flower head]] of a [[Helianthus annuus |sunflower]] is an example of the highly ordered structure that characterizes all [[living organism |organism]]s.<ref name = "urry2017a"/>]]
In [[biology]], one of the properties of [[life]] is its highly ''ordered'' structure,<ref name = "urry2017a">{{cite book | last1 = Urry | first1 = Lisa | last2 = Cain | first2 = Michael | last3 = Wasserman | first3 = Steven | last4 = Minorsky | first4 = Peter | last5 = Reece | first5 = Jane | chapter = Evolution, the themes of biology, and scientific inquiry | title = Campbell Biology | publisher = Pearson | edition = 11th | date = 2017 | location = New York | pages = 2–26 | isbn = 978-0134093413}}</ref> which can be observed at [[Biological organisation |multiple levels]] such as in [[cell (biology)|cell]]s, [[Tissue (biology)|tissue]]s, [[organ (anatomy)|organ]]s, and [[organism]]s. 

In another context, structure can also observed in [[macromolecule]]s, particularly [[protein]]s and [[nucleic acid]]s.<ref name ="banaszak2000">{{cite book|last1=Banaszak|first1=Leonard J.|title=Foundations of Structural Biology.|date=2000|publisher=Elsevier|location=Burlington|isbn=9780080521848}}</ref> The function of these molecules is determined by their shape as well as their composition, and their structure has multiple levels. [[Protein structure]] has a four-level hierarchy. The ''[[Protein primary structure|primary structure]]'' is the sequence of [[amino acid]]s that make it up. It has a [[peptide]] backbone made up of a repeated sequence of a nitrogen and two carbon atoms. The ''[[Protein secondary structure|secondary structure]]'' consists of repeated patterns determined by [[hydrogen bonding]]. The two basic types are the [[alpha helix|α-helix]] and the [[beta sheet|β-pleated sheet]]. The ''[[Protein tertiary structure|tertiary structure]]'' is a back and forth bending of the polypeptide chain, and the ''[[Protein quaternary structure|quaternary structure]]'' is the way that tertiary units come together and interact.<ref>{{cite book|last1=Purves|first1=William K.|last2=Sadava|first2=David E.|last3=Orians|first3=Gordon H.|last4=H. Craig|first4=Heller|title=Life, the science of biology|url=https://archive.org/details/lifesciencebiolo00purv_787|url-access=limited|date=2003|publisher=Sinauer Associates|location=Sunderland, Mass.|isbn=9780716798569|pages=[https://archive.org/details/lifesciencebiolo00purv_787/page/n43 41]–44|edition=7th}}</ref> [[Structural biology]] is concerned with [[biomolecular structure]] of macromolecules.<ref name ="banaszak2000"/>