Large Biomolecules
Chemistry: IB Diploma Higher Level, topic 2.8.6
Large Biomolecules
In large biomolecules, such as polypeptides (proteins), multiple non-covalent interactions can occur between different parts of the same biomolecule to stabilize the structure.
Amino acids
- Proteins are made of amino acids.
- Amino acids consits of a carboxylic acid croup, an amine group, and a variable R group.
- Neighboring amino acids are joined via peptide bonds between the amine and carboxylic acid group.
- Interactions between R groups creates the complex 3D tertiary structure of a protein.
- The 3D structure is usually coiled or folded.
Holding the 3D structure
- There are many weak and strong interactions that determine the final 3D shape of the protein (e.g. ionic bonds and hydrogen bonds).
- When the protein loses its 3D shape, it may no longer be functional.
- This 3D structure is known as the tertiary structure of the protein.
-min,w_800.jpg)
Ionic bonds
- Charged amino acids have a positively or negatively charged ion in their side chain.
- Charged amino acids can form relatively strong ionic bonds with other charged amino acids.
- Ionic bonds between amino acids are quite rare.
Hydrogen bonds
- Hydrogen bonds also form between amino acids.
- Hydrogen bonds are relatively weak but when there are many, the overall stability of the tertiary structure increases.
Hydrophobic interactions
- When protein folding takes place, the hydrophobic R groups of nonpolar amino acids lie in the interior of the protein, whereas the hydrophilic R groups lie on the outside.
- These types of interactions are also known as hydrophobic interactions.
Protein interactions
Test yourself on Large Biomolecules
Which of these statements about the tertiary structure of proteins are true?
Which of these is NOT a bond that gives rise to the tertiary structure?