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Tuesday 1 June 2004

biological structures; living structures

Definition : In biology, structures exist at all levels of biological organization , ranging hierarchically from the atomic and molecular to the cell , tissue , organ , organism , population and ecosystem level.

Usually, a higher-level structure is composed of multiple copies of a lower-level structure.

The structural biology studies the biomolecular structure of macromolecules, particularly proteins and nucleic acids.

The function of these molecules is determined by their shape as well as their composition, and their structure has multiple levels.

The protein structure has a four-level hierarchy. The primary structure is the sequence of amino acids that make it up. It has a peptide backbone made up of a repeated sequence of a nitrogen and two carbon atoms. The secondary structure consists of repeated patterns determined by hydrogen bonding. The two basic types are the α-helix and the β-pleated sheet. The tertiary structure is a back and forth bending of the polypeptide chain, and the quaternary structure is the way that tertiary units come together and interact.

The nucleic acids , the lipids and the carbohydrates also have biological structures and form the biological organization.


- biomolecular structures

- cells
- tissular components : tissular structures
- tissues
- organ components : organ structures
- organs : anatomical structures
- organ systems
-  body / organism / organisms

A structure has functions, that can be normal or pathological (functional anomalies).

A biostructure has biological functions, that can be normal or pathological (functional anomalies ).

A morphological anomaly of a structure is a lesion:

- molecular lesions
- cellular lesions
- tissular lesions
- organ lesions

Lesions can associate in lesional syndromes than can be observed in different diseases.

Each normal structure may be abnormal in pathological conditions :

- structure anomalies
- structure malformations
- structure lesions
- structure diseases
- structure tumors