Amino Acids, Proteins, Water and PH Flashcards
What is the structure of hydrogen bonds
Involves a linear arrangement of one hydrogen atom shared between two electronegative atoms
How are amino acids classified
According to the structures and properties of their side chains
All amino acids contain an alpha carbon bonded to what structures?
An amino group (-NH2) , a carboxyl group (-COOH), a hydrogen (-H), a side chain (-R)
What charge do hydrophobic amino acids have ?
No net charge
How do polar, uncharged amino acids differ from non polar amino acids?
They are soluble in water.
This class of amino acids contains those capable of creating redox sensitive disulfide bridges (cys)
They have at least one atom of N, O or S in the R side chain which can donate electron pairs to create hydrogen bonds
The hydroxyl group can be reversibly phosphorylated when incorporated into a protein backbone (eg tyr, ser, thr)
Properties of acidic amino acids
Hydrophilic
Carboxylic acid side group in side chain proton donating = acidifying
At physiological pH, all 3 groups ionised = charge difference -1
When ionised, side chains form ionic bond salt bridges and hydrogen bonds - often requires to bind metal ions.
Free glutamate functions as a neurotransmitter.
Properties of basic amino acids
Hydrophilic
Each side chain contains a basic group (proton accepting)
At physiological pH, ionisation of all 3 groups = charge difference +1
What does a peptide bond create?
A flat non-rotating structure known as the amide plane
What happens during the formation of the peptide bond ?
The a-amino group of one amino acid acts as a nucleophile to displace the hydroxyl group of another amino acid, forming a peptide bond. Water is removed
Where can polypeptides rotate ?
Around the angles between…
the a carbon and the amino group
the a carbon and the carboxyl group
(like a pack of cards linked at opposite corners)
