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Quizzes > Science

Amino Acid Abbreviations Quiz: 3-Letter Codes

Quick, free amino acid 3-letter quiz. Instant results.

Editorial: Review CompletedCreated By: Danielle Joseph LbvUpdated Aug 27, 2025
Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art style illustration for amino acid three letter code quiz on golden yellow background.

Use this amino acid abbreviations quiz to practice the 3-letter codes and spot lookalikes like Asn vs Asp and Ile vs Leu. Get instant feedback as you go, so you can fix weak spots before a test. For a wider review, try our amino acid quiz and browse biochemistry quiz questions.

What is the three-letter abbreviation for Alanine?
Ala
Asn
Arg
Asp
Alanine is abbreviated as Ala, derived from the first three letters of its name. It is a nonpolar, aliphatic amino acid commonly found in proteins. The code 'Ala' is universally used in biochemistry.
What is the three-letter abbreviation for Glycine?
Gly
Glyc
Gln
Glu
Glycine is the simplest amino acid and is abbreviated as Gly. It lacks a side chain beyond a hydrogen atom, making it achiral. The three-letter code 'Gly' is standard in protein nomenclature.
What is the three-letter abbreviation for Valine?
Vie
Val
Van
Vln
Valine is a branched-chain, nonpolar amino acid abbreviated as Val. Its abbreviation comes from the first three letters of the name. Valine is essential in the human diet.
What is the three-letter abbreviation for Leucine?
Lcn
Lue
Luc
Leu
Leucine is abbreviated as Leu, following the first three letters of its name. It is a hydrophobic, branched-chain amino acid crucial for protein synthesis. The code 'Leu' is standard in sequence notation.
What is the three-letter abbreviation for Isoleucine?
Iln
Ileu
Iso
Ile
Isoleucine is abbreviated as Ile, using the initial, third, and last letters of its name to distinguish it from Leu. It is an essential branched-chain amino acid. The code 'Ile' is universally recognized.
What is the three-letter abbreviation for Proline?
Prn
Ple
Pin
Pro
Proline, a cyclic, nonpolar amino acid, is abbreviated as Pro. It is unique in that its side chain bonds back to the backbone nitrogen. The three-letter code 'Pro' is the accepted standard.
What is the three-letter abbreviation for Serine?
Sre
Ser
Srn
Ses
Serine is abbreviated as Ser, derived from the first three letters of its name. It is a polar, uncharged amino acid with a hydroxyl group. The code 'Ser' is standard in protein sequences.
What is the three-letter abbreviation for Threonine?
Thr
The
Trn
Tht
Threonine is abbreviated as Thr, using the first, second, and fourth letters to differentiate it from other amino acids. It is a polar, uncharged, essential amino acid. The code 'Thr' is widely used.
What is the three-letter abbreviation for Cysteine?
Cys
Cyt
Cee
Cis
Cysteine is abbreviated as Cys, based on the first, third, and fourth letters of its name. It has a thiol side chain important for disulfide bond formation. The three-letter code 'Cys' is standard.
What is the three-letter abbreviation for Methionine?
Men
Meth
Mtn
Met
Methionine is abbreviated as Met, derived from the first three letters of its name. It is a sulfur-containing amino acid essential for initiating protein synthesis. The code 'Met' is universally accepted.
What is the three-letter abbreviation for Aspartic acid?
Atr
Asp
Apo
Asa
Aspartic acid is abbreviated as Asp, using the first three letters of its name. It is a negatively charged (acidic) amino acid at physiological pH. The code 'Asp' is standard in biochemical notation.
What is the three-letter abbreviation for Glutamic acid?
Glu
Gln
Glt
Gla
Glutamic acid is abbreviated as Glu, from the first three letters of its name. It is an acidic amino acid with a negatively charged side chain. The code 'Glu' is widely used in protein sequences.
What is the three-letter abbreviation for Phenylalanine?
Phn
Fen
Phe
PheA
Phenylalanine is abbreviated as Phe, based on the first, second, and fourth letters of its name. It is an aromatic, nonpolar amino acid. The code 'Phe' is standard in biochemistry.
What is the three-letter abbreviation for Asparagine?
Asn
Asp
Ala
Arg
Asparagine is a polar, uncharged amino acid abbreviated as Asn. It contains an amide side chain. The code 'Asn' is commonly used in protein notation.
What is the three-letter abbreviation for Glutamine?
Glt
Glu
Gln
Gin
Glutamine is abbreviated as Gln, derived from its name using key letters to avoid confusion with Glu. It is a polar, uncharged amino acid with an amide group.
What is the three-letter abbreviation for Arginine?
Arn
Agn
Argn
Arg
Arginine is a positively charged (basic) amino acid abbreviated as Arg. The code comes from the first three letters of its name. Arginine is important in the urea cycle.
What is the three-letter abbreviation for Lysine?
Lys
Lse
Lysn
Lyn
Lysine is a basic, positively charged amino acid abbreviated as Lys. The code 'Lys' comes from the first three letters of its name. Lysine is essential in human nutrition.
What is the three-letter abbreviation for Histidine?
Hsd
His
Hst
Hsn
Histidine is a basic amino acid with an imidazole side chain and is abbreviated as His. The code comes from the first three letters of its name. Histidine plays a key role in enzyme active sites.
What is the three-letter abbreviation for Tyrosine?
Try
Tye
Trp
Tyr
Tyrosine is an aromatic amino acid with a phenolic side chain and is abbreviated as Tyr. The code is derived from the first three letters of its name. Tyrosine is important in signaling pathways.
What is the three-letter abbreviation for Tryptophan?
Twp
Try
TrpH
Trp
Tryptophan is the largest aromatic amino acid and is abbreviated as Trp. The code uses key letters to distinguish it from Thr and Tyr. Trp is essential for serotonin biosynthesis.
Which amino acid is represented by the code Leu?
Leucine methyl ester
Leuprolide
Leucine
Lysine
The code Leu refers specifically to Leucine, a branched-chain, nonpolar amino acid. It is distinct from Lys (Lysine) and other compounds. Leucine is essential for muscle protein synthesis.
Which amino acid is represented by the code Ser?
Serine
Selenocysteine
Serotonin
Serotonin transporter
The code Ser indicates Serine, a polar, uncharged amino acid with a hydroxyl side chain. It is not to be confused with selenocysteine (Sec). Serine is essential in metabolism and signaling.
Which amino acid is represented by the code Pro?
Prostaglandin
Proline
Procollagen
Prolactin
Pro is the abbreviation for Proline, recognized for its cyclic structure that connects the side chain to the backbone nitrogen. It is not a hormone or prostaglandin. Proline is found in many structural proteins.
Which amino acid is represented by the code Met?
Methylamine
Methane
Methionine
Methadone
Met is the three-letter code for Methionine, a sulfur-containing essential amino acid. It should not be confused with small molecules like methane. Methionine is critical for initiating protein translation.
Which amino acid is represented by the code Phe?
Phenol
Phenylalanine
Phenylalanine ammonia-lyase
Phenytoin
Phe is the code for Phenylalanine, an aromatic amino acid. It is not an enzyme or small aromatic compound. Phenylalanine is a precursor for tyrosine and neurotransmitters.
Which amino acid is represented by the code Thr?
Thermolysin
Thrombin
Threonine
Threonine dehydrogenase
Thr refers to Threonine, a polar, uncharged, essential amino acid. It should not be confused with enzymes such as thrombin. Threonine is involved in protein phosphorylation.
What amino acid corresponds to the three-letter code Asn?
Aspartic acid
Arginine
Alanine
Asparagine
Asn is the code for Asparagine, a polar, uncharged amino acid with an amide side chain. It differs from Asp (Aspartic acid), which has a carboxylate side chain.
What amino acid corresponds to the three-letter code Gln?
Glutathione
Glutamic acid
Glutamine
Glycine
Gln is the abbreviation for Glutamine, a neutral, polar amino acid with an amide side chain. It is distinct from Glu (Glutamic acid), which is acidic.
What amino acid corresponds to the three-letter code Arg?
Alanine
Glutamine
Lysine
Arginine
Arg refers to Arginine, a basic amino acid with a guanidinium side chain. It is positively charged at physiological pH.
What amino acid corresponds to the three-letter code Lys?
Tyrosine
Threonine
Leucine
Lysine
Lys is the code for Lysine, a positively charged, basic amino acid with an ?-amino group. It is essential in humans.
What amino acid corresponds to the three-letter code His?
Hydroxyproline
Homoserine
Histidine
Histamine
His denotes Histidine, a basic amino acid containing an imidazole side chain that can act as a proton donor or acceptor.
What amino acid corresponds to the three-letter code Tyr?
Tryptophan
Threonine
Tyrosine kinase
Tyrosine
Tyr is the three-letter code for Tyrosine, an aromatic amino acid with a phenolic hydroxyl group. It is distinct from Trp and Thr.
What amino acid corresponds to the three-letter code Trp?
Tryptophan
Threonine
Tryptamine
Tyrosine
Trp is the abbreviation for Tryptophan, the largest aromatic amino acid with an indole side chain. It is distinct from Tyr and Thr.
Which three-letter code denotes the amino acid with a thiol side chain?
Thr
Ser
Cys
Met
Cys is the three-letter code for Cysteine, the only standard amino acid with a thiol ( - SH) group in its side chain. Met contains a thioether, not a thiol.
Which three-letter code denotes the acidic amino acid with the shorter side chain?
Asp
Asn
Gln
Glu
Asp is the code for Aspartic acid, which has one fewer methylene group than Glutamic acid (Glu). It is negatively charged at physiological pH.
Which three-letter code denotes the acidic amino acid with the longer side chain?
Asp
Gln
Glu
Asn
Glu stands for Glutamic acid, which has an extra methylene group compared to Aspartic acid (Asp). It is negatively charged at physiological pH.
Which three-letter code denotes the amino acid with an amide side chain and fewer methylene groups?
Asp
Glu
Gln
Asn
Asn is the code for Asparagine, which has an amide group and one fewer methylene group than Glutamine (Gln). It is polar and uncharged.
Which three-letter code denotes the amino acid with a guanidino functional group?
Gln
His
Arg
Lys
Arg represents Arginine, which contains a guanidinium group in its side chain, conferring a positive charge at physiological pH.
Which three-letter code denotes the amino acid with an indole ring?
Trp
Tyr
His
Phe
Trp is the code for Tryptophan, which contains an indole aromatic ring. This distinguishes it from other aromatic amino acids such as Tyr and Phe.
Which of the following three-letter codes is NOT a standard amino acid abbreviation?
Ile
Pro
Sec
Val
Sec is the code for selenocysteine, the 21st amino acid, and not one of the 20 standard amino acids. Standard codes include Ile, Pro, and Val.
Which three-letter code represents pyrrolysine, the genetically encoded 22nd amino acid?
Pro
Pyl
Phe
Pyls
Pyl is the code for pyrrolysine, the 22nd amino acid found in some methanogenic archaea. It is not one of the standard 20 amino acids.
Which three-letter code is used when an amino acid residue is unspecified or unknown in protein data?
Unk
Any
Xxx
Xaa
Xaa is the IUPAC code for an unspecified or unknown amino acid residue in protein sequences. This notation avoids misassignment.
In the IUPAC three-letter code system, which code represents the amino acid with a secondary amine in its side chain?
Pro
His
Lys
Arg
Proline (Pro) is unique among standard amino acids because its side chain forms a secondary amine by bonding back to the backbone nitrogen. No other standard residue has this feature.
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Study Outcomes

  1. Recall Three-Letter Codes -

    Quiz takers will be able to accurately recall the three-letter amino acid abbreviation for each of the 20 common amino acids, reinforcing their biochemical terminology.

  2. Identify Key Abbreviations -

    Participants will pinpoint specific abbreviations such as the asparagine abbreviation (Asn), isoleucine abbreviation (Ile), and trp amino acid abbreviations (Trp) with confidence.

  3. Match Names and Abbreviations -

    Users will master matching full amino acid names to their corresponding three-letter codes, improving speed and accuracy in naming conventions.

  4. Decode Peptide Sequences -

    After the quiz, learners can apply their knowledge to interpret short peptide sequences using three-letter abbreviations in real-world biochemistry contexts.

  5. Build Biochemistry Vocabulary -

    Participants will expand and solidify their biochemistry vocabulary, boosting confidence in both academic study and professional communication.

Cheat Sheet

  1. IUPAC-Standard Three-Letter System -

    The official IUPAC three-letter amino acid abbreviation system assigns codes based on the amino acid's full name, such as Gly for glycine and Ala for alanine. These 3 letter abbreviations for amino acids are used universally in protein databases and publications. Mastery of this system ensures accurate reading of peptide sequences in research contexts.

  2. Asparagine vs Aspartic Acid: Asn and Asp -

    Asparagine (Asn) is the amide form of aspartate (Asp), so remember Asn ends with 'n' for 'amide', while Asp ends with 'p' for 'acid'. This simple mnemonic clarifies the asparagine abbreviation and helps avoid confusion in enzyme active site annotations. University biochemistry courses often emphasize this distinction when mapping post-translational modifications.

  3. Isoleucine and Leucine: Ile vs Leu -

    The isoleucine abbreviation is Ile, differentiating it from leucine (Leu) despite their similar names and hydrophobic side chains. A handy trick is that Ile has an 'i' at the start, while Leu flips to 'e' in the second position. Recognizing this pattern is crucial when analyzing hydrophobic cores in protein structures.

  4. Aromatic Giants: Phe, Tyr, Trp -

    The aromatic amino acids phenylalanine (Phe), tyrosine (Tyr), and tryptophan (Trp) all possess ring structures; remember "FYT-rp" as a flash cue for Phe, Tyr, Trp. Focusing on trp amino acid abbreviations (Trp) underscores tryptophan's bulky indole ring, which quenches fluorescence in proteins. Reputable journals often discuss these residues in the context of UV absorbance at 280 nm.

  5. Classification Mnemonics for Quick Recall -

    Grouping amino acids by polarity and charge can speed up learning: use "GAVLIMP" for nonpolar, "STCNQ" for polar uncharged, "DE" for acidic, and "KRH" for basic. A useful phrase is "Go And Visit London In May; Stay The Nice Dad's Kind Regards" to cover all three-letter codes. Such mnemonic devices, endorsed by many academic resources, boost retention during exams and lab work.

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