Amino Acids and Their Properties

These flashcards capture key concepts related to amino acids, including classification, structure, properties, and interactions relevant to their behavior in biological systems.

What are amino acids classified by their side chain structures?

Amino acids can be classified as nonpolar, uncharged polar, ionized, and partially ionized based on the chemistry of their R groups.

What is the significance of pKa values in amino acids?

The pKa values of the ionizable groups in amino acids are critical to their properties when part of a polypeptide, influencing their behavior based on local environmental conditions.

How are amino acids represented in sequences?

Amino acids are represented using three-letter abbreviations and one-letter codes for easier identification and memorization.

What is the general structure of an α-amino acid?

An α-amino acid has a primary amino group (─NH2) attached to the α carbon, which is adjacent to the carboxylic acid group (─COOH).

Name the types of bonds that can form from amino acids.

Amino acids can form peptide bonds through condensation reactions, resulting in amide linkages that create polypeptides.

What are the two non-standard amino acids mentioned?

Selenocysteine and pyrrolysine are two non-standard amino acids that are incorporated during protein synthesis using a repurposed stop codon.

What is the concept of the isoelectric point (pI)?

The isoelectric point (pI) is the pH at which an amino acid has no net charge, which can be calculated using the averages of the pKa values surrounding the zwitterionic state.

What types of interactions stabilize protein structures involving amino acids?

Ionic interactions, hydrogen bonding, and London dispersion forces play key roles in stabilizing the folded structures of proteins.

What happens to amino acids in a polar versus a nonpolar environment?

Ionizable amino acids will have different pKa values and behaviors in polar versus nonpolar environments, affecting their ionization and interactions.

How can amino acids be separated based on their properties?

Amino acids can be separated by hydrophobic interactions chromatography for nonpolar and polar interactions, and by ion exchange chromatography for charge differences.

What are amino acids classified by their side chain structures?

Amino acids can be classified as nonpolar, uncharged polar, ionized, and partially ionized based on the chemistry of their R groups.

What is the significance of pKa values in amino acids?

The pKa values of the ionizable groups in amino acids are critical to their properties when part of a polypeptide, influencing their behavior based on local environmental conditions.

How are amino acids represented in sequences?

Amino acids are represented using three-letter abbreviations and one-letter codes for easier identification and memorization.

What is the general structure of an α-amino acid?

An α-amino acid has a primary amino group (─NH_{2}) attached to the α carbon, which is adjacent to the carboxylic acid group (─COOH).

Name the types of bonds that can form from amino acids.

Amino acids can form peptide bonds through condensation reactions, resulting in amide linkages that create polypeptides.

What are the two non-standard amino acids mentioned?

Selenocysteine and pyrrolysine are two non-standard amino acids that are incorporated during protein synthesis using a repurposed stop codon.

What is the concept of the isoelectric point (pI)?

The isoelectric point (pI) is the pH at which an amino acid has no net charge, which can be calculated using the averages of the pKa values surrounding the zwitterionic state.

What types of interactions stabilize protein structures involving amino acids?

Ionic interactions, hydrogen bonding, and London dispersion forces play key roles in stabilizing the folded structures of proteins.

What happens to amino acids in a polar versus a nonpolar environment?

Ionizable amino acids will have different pKa values and behaviors in polar versus nonpolar environments, affecting their ionization and interactions.

How can amino acids be separated based on their properties?

Amino acids can be separated by hydrophobic interactions chromatography for nonpolar and polar interactions, and by ion exchange chromatography for charge differences.

Which amino acids have nonpolar side chains?

• Glycine (Gly, G)

• Alanine (Ala, A)

• Valine (Val, V)

• Leucine (Leu, L)

• Isoleucine (Ile, I)

• Methionine (Met, M)

• Phenylalanine (Phe, F)

• Tryptophan (Trp, W)

• Proline (Pro, P)

Which amino acids have uncharged polar side chains?

The amino acids with uncharged polar side chains include:

• Serine (Ser, S)
• Threonine (Thr, T)
• Cysteine (Cys, C)
• Tyrosine (Tyr, Y)
• Asparagine (Asn, N)
• Glutamine (Gln, Q)

Which amino acids have ionized polar side chains?

Ionized polar side chains are categorized by their charge at physiological pH:

• Positively charged (basic): Lysine (Lys, K), Arginine (Arg, R), Histidine (His, H)
• Negatively charged (acidic): Aspartic acid (Asp, D), Glutamic acid (Glu, E)