40 Questions
What is the term used to describe substances that can act as both acids and bases?
Ampholytes
At what pH does an amino acid carry a +ve charge on the amino group and no charge on the COOH group?
pH < 3
What is the term used to describe the pH at which an amino acid has a net electric charge of zero?
Isoelectric point (pI)
What is the reaction between the COOH group of an amino acid and ammonia (NH3)?
Amide formation
What type of reaction occurs when an amino acid reacts with a base?
Salt formation
What is the term used to describe the ion that an amino acid exists as in solution?
Zwitterion
What is the name of the amino acid that has an isoelectric point equal to the arithmetic mean of the two pKa values?
Glycine
What type of reaction occurs when an amino acid undergoes decarboxylation?
Decarboxylation to form an amine
What type of bond joins amino acid residues in proteins?
Covalent bond
In addition to protein synthesis, what is another function of amino acids and their derivatives?
Nerve transmission
What are short polymers of amino acids called?
Peptides
Which of the following types of proteins can be found in the human body?
Antibodies
What do proteins yield upon complete hydrolysis?
L-α amino acids
What is the nature of the side chain attached to an alpha carbon atom in amino acids (excluding proline)?
A distinctive 'R-group'
At physiological pH, what happens to the amino group in amino acids?
It gets protonated to form –NH3+
What property does a carbon atom exhibit if it is attached to four different groups?
Optical isomerism
Which amino acid does not have optical isomers?
Glycine
Which type of amino acids are proteins composed of?
L-α amino acids
What characteristic do the R groups of alanine, valine, leucine, and isoleucine share?
They are hydrophobic
What makes proline unique among amino acids?
It has an imino group
Which sulfur-containing amino acid is mentioned?
Methionine
What type of interactions help cluster the side chains of alanine, valine, leucine, and isoleucine within proteins?
Hydrophobic interactions
Which amino acid has an R group that is simply a hydrogen atom?
Glycine
Why are the R groups of certain amino acids more soluble in water than nonpolar amino acids?
They contain functional groups that form hydrogen bonds with water
What is formed when α-amino acids react with ninhydrin?
Ruhemann’s purple
What is the process called when an amino group is transferred from an amino acid to a keto acid?
Transamination
What happens during oxidative deamination?
Free ammonia is liberated
Which amino acids are present in collagen, the most abundant protein in mammals?
4-hydroxyproline and 5-hydroxylysine
Which amino acid found in histones can undergo modifications such as methylation, phosphorylation, or acetylation?
Many amino acids
Which plasma protein is involved in blood clotting and contains γ-carboxyglutamic acid?
Certain plasma proteins
Which type of amino acids is the majority isolated from animals and plants?
L-category
Which amino acids are specifically found in certain antibiotics like actinomycin-D?
D-amino acids
Which amino acids are exclusively ketogenic?
Leucine and Lysine
Which amino acids are both ketogenic and glucogenic?
Isoleucine, Phenylalanine, Tyrosine, and Tryptophan
What makes selenocysteine unique among amino acids?
It incorporates selenium in place of sulfur
How is pyrrolysine chemically characterized?
It has a pyrroline ring linked to the end of the lysine side chain
At what codon is selenocysteine incorporated during protein translation?
UGA
Which characteristic is common to most amino acids?
Solubility in water
Which amino acid is typically tasteless?
Leucine
Which property is common to all amino acids except glycine?
Possessing optical isomers
This quiz explores the role of amino acids in protein synthesis, their participation in cellular functions, and their derivatives.
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