28 Questions
What type of bond is formed between amino acids to create peptides?
Peptide bond
What is the result of the formation of a peptide bond?
Release of water
Which term best describes the characteristics of a peptide bond?
Rigid and planar
In the dipeptide valylalanine, what type of configuration does the peptide bond have?
Trans configuration
What is the charge characteristic of a peptide bond?
Uncharged but polar
At what pH does leucine exist as a cation?
Above 6
What is the isoelectric pH of leucine when it exists as a zwitterion?
6.0
What is the pKa of glutamic acid?
9.67
Which amino acid has a pl of 12.03?
Alanine
What type of bond links amino acids in peptides?
Peptide bond
Which amino acid has the highest pK₂ value among those mentioned?
Isoleucine
Which amino acid is categorized as an aromatic amino acid?
Tyrosine
Between Alanine and Glycine, which amino acid has a higher pK₁ value?
Glycine
Which amino acid has the lowest pK value among those mentioned?
Serine
Among Alanine, Valine, and Isoleucine, which one has the closest pK values to each other?
Valine
Which amino acid is formed by the condensation of two molecules of cysteine?
Cystine
Which property distinguishes proline from other amino acids?
Having an imino group (=NH)
What is the distinguishing characteristic of proline as an amino acid?
Being an a-imino acid
What property enables amino acids to have optical isomers?
Presence of asymmetric carbon atom
What is the common solubility characteristic of most amino acids?
Usually soluble in water and insoluble in organic solvents
Which amino acid property often results in melting points above 200°C?
Presence of pyrrolidine ring
What dual characteristic do amino acids possess that make them ampholytes?
Acidic and basic properties
What term is used to describe amino acids due to their ability to donate or accept a proton?
Ampholytes
At strongly acidic pH, how is an amino acid charged?
Positively (cation)
What is the isoelectric point (pl) of an amino acid?
The pH at which it carries both positive and negative charges
How is an amino acid charged at strongly alkaline pH?
Negatively (anion)
How can the isoelectric point (pl) of an amino acid be calculated?
By taking the average pKa values corresponding to the ionizable groups
What is the term used for a molecule that exists as a hybrid molecule containing positive and negative ionic groups?
Zwitterion
This quiz covers the amino acids glycine, alanine, valine, leucine, isoleucine, and hydroxyl group-containing amino acids like serine, threonine, and tyrosine. It includes their names, symbols, structural formulas, and pKa values for α-COOH and α-NH₂.
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