Amino Acids - Chapter 3 Flashcards
What is the general structure of an amino acid?
An amino acid has a central carbon (α-carbon) bonded to an amino group (-NH₂), a carboxyl group (-COOH), a hydrogen atom, and a unique side chain (R group).
What are the two forms of amino acids in biological systems?
Amino acids exist in two enantiomeric forms: L-form and D-form. Biological systems predominantly use L-form amino acids.
How is the side chain (R group) of an amino acid important?
The side chain (R group) determines the amino acid’s properties, such as its polarity, charge, size, and hydrophobicity or hydrophilicity.
What are the three main classifications of amino acids based on their side chains?
Amino acids can be classified as nonpolar (hydrophobic), polar (hydrophilic), and charged (acidic or basic).
List the amino acids with nonpolar, aliphatic side chains.
Glycine, alanine, valine, leucine, isoleucine, and proline.
Which amino acids contain aromatic side chains?
Phenylalanine, tyrosine, tryptophan, and histidine
What are the amino acids with polar, uncharged side chains?
Serine, threonine, asparagine, glutamine, and cysteine.
Which amino acids are classified as acidic due to their side chains?
Aspartate and glutamate
Name the amino acids with basic side chains.
Lysine, arginine, and histidine.
What is the significance of the pKa values of the amino and carboxyl groups in amino acids?
The pKa values determine the ionization state of the amino acid at different pH levels, influencing its charge and interactions.
What is the concept of isoelectric point (pI) in amino acids?
The isoelectric point (pI) is the pH at which an amino acid has no net charge and exists predominantly in its zwitterionic form.
Why are amino acids important to protein structure?
Amino acids are the building blocks of proteins. Their sequence and chemical properties determine the protein’s structure and function, including primary, secondary, tertiary, and quaternary structures.
What is a peptide bond and how is it formed?
A peptide bond is a covalent bond formed between the carboxyl group of one amino acid and the amino group of another, releasing a molecule of water.
What is the significance of post-translational modifications of amino acids?
Post-translational modifications can alter protein function, stability, localization, and interactions, and include processes like phosphorylation, glycosylation, and acetylation.
How do amino acid side chains contribute to enzyme function?
Side chains can participate in substrate binding, catalysis, and stabilization of transition states, playing crucial roles in enzyme activity.
Is glycine hydrophobic or hydrophilic? Is it charged?
hydrophobic, uncharged
Is alanine hydrophobic or hydrophilic? Is it charged?
hydrophobic, uncharged
Is valine hydrophobic or hydrophilic? Is it charged?
hydrophobic, uncharged
Is leucine hydrophobic or hydrophilic? Is it charged?
hydrophobic, uncharged
Is isoleucine hydrophobic or hydrophilic? Is it charged?
hydrophobic, uncharged
Is methionine hydrophobic or hydrophilic? Is it charged?
hydrophobic, uncharged
Is phenylalanine hydrophobic or hydrophilic? Is it charged?
hydrophobic, uncharged
Is tryptophan hydrophobic or hydrophilic? Is it charged?
hydrophobic, uncharged
Is proline hydrophobic or hydrophilic? Is it charged?
hydrophobic, uncharged
