MCAT Biochemistry 1.1

Flashcards on Amino Acids

What are the 4 groups attached to the central "alpha" carbon of a proteinogenic amino acid?

Amino group (-NH₂), Carboxyl group (-COOH), Hydrogen atom (H), Side chain (R group)

What is the stereochemistry of the chiral amino acids that appear in eukaryotic proteins?

In eukaryotic proteins, chiral amino acids all have the L-stereochemistry (except glycine, which is achiral).

Stereochemistry

The branch of chemistry that studies the 3D arrangement of atoms in molecules and how that arrangement affects their chemical behavior and interactions.

What is the difference between L and D amino acids?

L-amino acids have the amino group on the left in a Fischer projection. D-amino acids have the amino group on the right in the same projection.

What are some key points about L and D amino acids?

L-amino acids are the ones used to make proteins in living organisms (especially in eukaryotes). D-amino acids are rare in nature but do appear in bacterial cell walls and some antibiotics.

What is the difference between (R) and (S) configurations?

(R) = Rectus = Latin for "right" ' atoms are arranged clockwise. (S) = Sinister = Latin for "left" ' atoms are arranged counterclockwise.

Which amino acids fit into each of these categories: Nonpolar, nonaromatic? Aromatic? Polar? Negatively charged/acidic? Positively charged/basic?

Nonpolar, nonaromatic (7): Glycine (Gly), Alanine (Ala), Valine (Val), Leucine (Leu), Isoleucine (Ile), Methionine (Met), Proline (Pro). Aromatic (3): Phenylalanine (Phe), Tyrosine (Tyr), Tryptophan (Trp). Polar (5): Serine (Ser), Threonine (Thr), Asparagine (Asn), Glutamine (Gln), Cysteine (Cys). Negatively charged/acidic (2): Aspartate (Asp), Glutamate (Glu). Positively charged/basic (3): Lysine (Lys), Arginine (Arg), Histidine (His)

Where do hydrophobic amino acids tend to reside within a protein? What about hydrophilic ones?

Hydrophobic amino acids tend to cluster inside the protein, away from water. Hydrophilic amino acids usually face outward, interacting with water or other polar molecules.

Identify Alanine by its structure and one-letter abbreviation.

Alanine (A) Structure: CH₃-CH(NH₂)-COOH

Identify Arginine by its structure and one-letter abbreviation.

Arginine (R) Structure: NH₂-C(NH)-NH-(CH₂)₃-COOH

Identify Asparagine by its structure and one-letter abbreviation.

Asparagine (N) Structure: H₂N-CO-CH₂-COOH

Identify Aspartate by its structure and one-letter abbreviation.

Aspartate (D) Structure: HOOC-CH₂-COOH

Identify Cysteine by its structure and one-letter abbreviation.

Cysteine (C) Structure: HS-CH₂-COOH

Identify Glutamine by its structure and one-letter abbreviation.

Glutamine (Q) Structure: H₂N-CO-(CH₂)₂-COOH

Identify Glutamate by its structure and one-letter abbreviation.

Glutamate (E) Structure: HOOC-(CH₂)₂-COOH

Identify Glycine by its structure and one-letter abbreviation.

Glycine (G) Structure: H-CH(NH₂)-COOH

Identify Histidine by its structure and one-letter abbreviation.

Histidine (H) Structure: C₆H₃N₂-CH₂-COOH

Identify Isoleucine by its structure and one-letter abbreviation.

Isoleucine (I) Structure: CH₃-CH₂-CH(NH₂)-COOH

Identify Leucine by its structure and one-letter abbreviation.

Leucine (L) Structure: CH₃-CH₂-CH(NH₂)-COOH

Identify Lysine by its structure and one-letter abbreviation.

Lysine (K) Structure: H₂N-(CH₂)₄-COOH

Identify Methionine by its structure and one-letter abbreviation.

Methionine (M) Structure: CH₃-S-CH₂-CH₂-COOH

Identify Phenylalanine by its structure and one-letter abbreviation.

Phenylalanine (F) Structure: C₆H₅-CH₂-COOH

Identify Proline by its structure and one-letter abbreviation.

Proline (P) Structure: (CH₂)₃-NH-COOH

Identify Serine by its structure and one-letter abbreviation.

Serine (S) Structure: HO-CH₂-COOH

Identify Threonine by its structure and one-letter abbreviation.

Threonine (T) Structure: CH₃-CH(OH)-COOH

Identify Tryptophan by its structure and one-letter abbreviation.

Tryptophan (W) Structure: C₈H₆N-CH₂-COOH

Identify Tyrosine by its structure and one-letter abbreviation.

Tyrosine (Y) Structure: C₆H₄OH-CH₂-COOH

Identify Valine by its structure and one-letter abbreviation.

Valine (V) Structure: CH₃-CH(CH₃)-COOH