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Amino Acid Flashcards: 20 Side-Chain Structures & Codes

Learn the 20 standard amino acids with 120 flashcards for side-chain recognition and drawing, plus one- and three-letter code recall in both directions.

By author Flashcards Open Source App

About this deck

These amino acid flashcards train the 20 standard amino acids as six separate recall tasks. You’ll practice side-chain structure → amino-acid name, amino-acid name → side-chain drawing, amino-acid name → three-letter code, three-letter code → amino-acid name, amino-acid name → one-letter code, and one-letter code → amino-acid name. Each target has its own card, so remembering a code never hides a missed structure.

The structure cards show only the variable side chain. A small Cα attachment marker fixes the convention without turning the shared amino-acid backbone into another recognition task; proline also shows the side chain’s connection to the backbone nitrogen. The diagrams use one neutral connectivity convention. They do not test pH-dependent charge states or stereochemistry.

The fixed sequence introduces each structure before its drawing prompt and each code before its reverse lookup for the same amino acid. It interleaves all six directions, keeps every same-amino-acid variant at least three unrelated cards apart, and separates visually or code-confusable concepts. The review scheduler handles longer-term spacing after installation.

The deck deliberately leaves out side-chain class labels because classification schemes vary. It also excludes pKa values, charge-state tables, isoelectric points, codons, nutrition categories, full-backbone recognition, nonstandard amino acids and ambiguous sequence symbols, peptide-bond and protein-folding trivia, and exam, clinical, disease, supplement, dietary, or pronunciation material. Those mappings either vary by convention or belong outside this focused side-chain-and-code recall set.

IUPAC-IUB nomenclature recommendations, NCBI’s overview of amino acids and their side chains, and the NCBI amino-acid code table were used only to verify common-knowledge facts. All prompts, answers, selection, order, molecular diagrams, metadata, and cover composition were created independently. No source or competitor prose, images, screenshots, trade dress, or logos were copied. Facts are not claimed as proprietary. The original wording, organization, metadata, diagrams, and cover are dedicated under CC0 1.0 to the extent applicable rights exist.

Cards in this deck

  1. Card 1

    Question

    Side-chain diagram showing CH₂ joined to a five-membered ring containing NH and N from the Cα attachment marker.

    Which amino acid has this side chain?

    Answer

    Histidine — side chain: Cα–CH₂–imidazolyl.

  2. Card 2

    Question

    Valine → three-letter code

    Answer

    Val

  3. Card 3

    Question

    Serine → one-letter code

    Answer

    S

  4. Card 4

    Question

    Side-chain diagram showing CH₂–C(=O)–NH₂ from the Cα attachment marker.

    Which amino acid has this side chain?

    Answer

    Asparagine — side chain: Cα–CH₂–C(=O)–NH₂.

  5. Card 5

    Question

    Phenylalanine → three-letter code

    Answer

    Phe

  6. Card 6

    Question

    Lysine → one-letter code

    Answer

    K

  7. Card 7

    Question

    Side-chain diagram showing one CH₃ group bonded to the Cα attachment marker.

    Which amino acid has this side chain?

    Answer

    Alanine — side chain: Cα–CH₃.

  8. Card 8

    Question

    Isoleucine → three-letter code

    Answer

    Ile

  9. Card 9

    Question

    Cysteine → one-letter code

    Answer

    C

  10. Card 10

    Question

    Side-chain diagram showing CH₂–C(=O)–OH from the Cα attachment marker.

    Which amino acid has this side chain?

    Answer

    Aspartate — side chain: Cα–CH₂–C(=O)–OH.

  11. Card 11

    Question

    Tyrosine → three-letter code

    Answer

    Tyr

  12. Card 12

    Question

    Arginine → one-letter code

    Answer

    R

  13. Card 13

    Question

    Side-chain diagram showing three CH₂ groups linking the Cα and Nα attachment markers.

    Which amino acid has this side chain?

    Answer

    Proline — side chain: Cα–(CH₂)₃–Nα.

  14. Card 14

    Question

    Leucine → three-letter code

    Answer

    Leu

  15. Card 15

    Question

    Threonine → one-letter code

    Answer

    T

  16. Card 16

    Question

    Side-chain diagram showing CH₂–CH₂–C(=O)–NH₂ from the Cα attachment marker.

    Which amino acid has this side chain?

    Answer

    Glutamine — side chain: Cα–CH₂–CH₂–C(=O)–NH₂.

  17. Card 17

    Question

    Tryptophan → three-letter code

    Answer

    Trp

  18. Card 18

    Question

    Methionine → one-letter code

    Answer

    M

  19. Card 19

    Question

    Side-chain diagram showing a hydrogen bonded to the Cα attachment marker.

    Which amino acid has this side chain?

    Answer

    Glycine — side chain: Cα–H.

  20. Card 20

    Question

    Glutamate → three-letter code

    Answer

    Glu

  21. Card 21

    Question

    Val → amino-acid name

    Answer

    Valine

  22. Card 22

    Question

    S → amino-acid name

    Answer

    Serine

  23. Card 23

    Question

    Asparagine → three-letter code

    Answer

    Asn

  24. Card 24

    Question

    Phenylalanine → one-letter code

    Answer

    F

  25. Card 25

    Question

    Side-chain diagram showing (CH₂)₄–NH₂ from the Cα attachment marker.

    Which amino acid has this side chain?

    Answer

    Lysine — side chain: Cα–(CH₂)₄–NH₂.

  26. Card 26

    Question

    Alanine → draw or recall the side chain

    Answer

    Side-chain diagram showing one CH₃ group bonded to the Cα attachment marker.

    Side chain: Cα–CH₃.

  27. Card 27

    Question

    Ile → amino-acid name

    Answer

    Isoleucine

  28. Card 28

    Question

    C → amino-acid name

    Answer

    Cysteine

  29. Card 29

    Question

    Aspartate → three-letter code

    Answer

    Asp

  30. Card 30

    Question

    Tyrosine → one-letter code

    Answer

    Y

  31. Card 31

    Question

    Side-chain diagram showing (CH₂)₃–NH–C(=NH)–NH₂ from the Cα attachment marker.

    Which amino acid has this side chain?

    Answer

    Arginine — side chain: Cα–(CH₂)₃–NH–C(=NH)–NH₂.

  32. Card 32

    Question

    Proline → draw or recall the side chain

    Answer

    Side-chain diagram showing three CH₂ groups linking the Cα and Nα attachment markers.

    Side chain: Cα–(CH₂)₃–Nα.

  33. Card 33

    Question

    Leu → amino-acid name

    Answer

    Leucine

  34. Card 34

    Question

    T → amino-acid name

    Answer

    Threonine

  35. Card 35

    Question

    Glutamine → three-letter code

    Answer

    Gln

  36. Card 36

    Question

    Tryptophan → one-letter code

    Answer

    W

  37. Card 37

    Question

    Side-chain diagram showing CH₂–CH₂–S–CH₃ from the Cα attachment marker.

    Which amino acid has this side chain?

    Answer

    Methionine — side chain: Cα–CH₂–CH₂–S–CH₃.

  38. Card 38

    Question

    Glycine → draw or recall the side chain

    Answer

    Side-chain diagram showing a hydrogen bonded to the Cα attachment marker.

    Side chain: Cα–H.

  39. Card 39

    Question

    Glu → amino-acid name

    Answer

    Glutamate

  40. Card 40

    Question

    Histidine → draw or recall the side chain

    Answer

    Side-chain diagram showing CH₂ joined to a five-membered ring containing NH and N from the Cα attachment marker.

    Side chain: Cα–CH₂–imidazolyl.

  41. Card 41

    Question

    K → amino-acid name

    Answer

    Lysine

  42. Card 42

    Question

    Alanine → three-letter code

    Answer

    Ala

  43. Card 43

    Question

    Isoleucine → one-letter code

    Answer

    I

  44. Card 44

    Question

    Side-chain diagram showing CH₂–SH from the Cα attachment marker.

    Which amino acid has this side chain?

    Answer

    Cysteine — side chain: Cα–CH₂–SH.

  45. Card 45

    Question

    Aspartate → draw or recall the side chain

    Answer

    Side-chain diagram showing CH₂–C(=O)–OH from the Cα attachment marker.

    Side chain: Cα–CH₂–C(=O)–OH.

  46. Card 46

    Question

    Tyr → amino-acid name

    Answer

    Tyrosine

  47. Card 47

    Question

    R → amino-acid name

    Answer

    Arginine

  48. Card 48

    Question

    Proline → three-letter code

    Answer

    Pro

  49. Card 49

    Question

    Leucine → one-letter code

    Answer

    L

  50. Card 50

    Question

    Side-chain diagram showing CH bonded to OH and CH₃ from the Cα attachment marker.

    Which amino acid has this side chain?

    Answer

    Threonine — side chain: Cα–CH(OH)–CH₃.

  51. Card 51

    Question

    Glutamine → draw or recall the side chain

    Answer

    Side-chain diagram showing CH₂–CH₂–C(=O)–NH₂ from the Cα attachment marker.

    Side chain: Cα–CH₂–CH₂–C(=O)–NH₂.

  52. Card 52

    Question

    Trp → amino-acid name

    Answer

    Tryptophan

  53. Card 53

    Question

    M → amino-acid name

    Answer

    Methionine

  54. Card 54

    Question

    Glycine → three-letter code

    Answer

    Gly

  55. Card 55

    Question

    Glutamate → one-letter code

    Answer

    E

  56. Card 56

    Question

    Histidine → three-letter code

    Answer

    His

  57. Card 57

    Question

    Valine → one-letter code

    Answer

    V

  58. Card 58

    Question

    Side-chain diagram showing CH₂–OH from the Cα attachment marker.

    Which amino acid has this side chain?

    Answer

    Serine — side chain: Cα–CH₂–OH.

  59. Card 59

    Question

    Asparagine → draw or recall the side chain

    Answer

    Side-chain diagram showing CH₂–C(=O)–NH₂ from the Cα attachment marker.

    Side chain: Cα–CH₂–C(=O)–NH₂.

  60. Card 60

    Question

    Phe → amino-acid name

    Answer

    Phenylalanine

    Abstract molecular study scene with colorful ball-and-stick side-chain forms arranged around an open center.

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    Amino Acid Flashcards: 20 Side-Chain Structures & Codes

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  61. Card 61

    Question

    I → amino-acid name

    Answer

    Isoleucine

  62. Card 62

    Question

    Cysteine → draw or recall the side chain

    Answer

    Side-chain diagram showing CH₂–SH from the Cα attachment marker.

    Side chain: Cα–CH₂–SH.

  63. Card 63

    Question

    Aspartate → one-letter code

    Answer

    D

  64. Card 64

    Question

    Side-chain diagram showing CH₂ joined to a six-membered ring with an opposite OH group from the Cα attachment marker.

    Which amino acid has this side chain?

    Answer

    Tyrosine — side chain: Cα–CH₂–C₆H₄–OH (para).

  65. Card 65

    Question

    Arginine → three-letter code

    Answer

    Arg

  66. Card 66

    Question

    Pro → amino-acid name

    Answer

    Proline

  67. Card 67

    Question

    L → amino-acid name

    Answer

    Leucine

  68. Card 68

    Question

    Threonine → draw or recall the side chain

    Answer

    Side-chain diagram showing CH bonded to OH and CH₃ from the Cα attachment marker.

    Side chain: Cα–CH(OH)–CH₃.

  69. Card 69

    Question

    Glutamine → one-letter code

    Answer

    Q

  70. Card 70

    Question

    Side-chain diagram showing the Cα attachment marker joined through CH₂ to position 3 of fused five- and six-membered rings containing NH.

    Which amino acid has this side chain?

    Answer

    Tryptophan — side chain: Cα–CH₂–indol-3-yl.

  71. Card 71

    Question

    Methionine → three-letter code

    Answer

    Met

  72. Card 72

    Question

    Gly → amino-acid name

    Answer

    Glycine

  73. Card 73

    Question

    E → amino-acid name

    Answer

    Glutamate

  74. Card 74

    Question

    His → amino-acid name

    Answer

    Histidine

  75. Card 75

    Question

    V → amino-acid name

    Answer

    Valine

  76. Card 76

    Question

    Serine → draw or recall the side chain

    Answer

    Side-chain diagram showing CH₂–OH from the Cα attachment marker.

    Side chain: Cα–CH₂–OH.

  77. Card 77

    Question

    Asparagine → one-letter code

    Answer

    N

  78. Card 78

    Question

    Side-chain diagram showing CH₂ joined to a six-membered ring with alternating double bonds from the Cα attachment marker.

    Which amino acid has this side chain?

    Answer

    Phenylalanine — side chain: Cα–CH₂–C₆H₅.

  79. Card 79

    Question

    Lysine → three-letter code

    Answer

    Lys

  80. Card 80

    Question

    Ala → amino-acid name

    Answer

    Alanine

  81. Card 81

    Question

    Proline → one-letter code

    Answer

    P

  82. Card 82

    Question

    Side-chain diagram showing CH₂–CH with two terminal CH₃ branches from the Cα attachment marker.

    Which amino acid has this side chain?

    Answer

    Leucine — side chain: Cα–CH₂–CH(CH₃)₂.

  83. Card 83

    Question

    Threonine → three-letter code

    Answer

    Thr

  84. Card 84

    Question

    Gln → amino-acid name

    Answer

    Glutamine

  85. Card 85

    Question

    W → amino-acid name

    Answer

    Tryptophan

  86. Card 86

    Question

    Methionine → draw or recall the side chain

    Answer

    Side-chain diagram showing CH₂–CH₂–S–CH₃ from the Cα attachment marker.

    Side chain: Cα–CH₂–CH₂–S–CH₃.

  87. Card 87

    Question

    Glycine → one-letter code

    Answer

    G

  88. Card 88

    Question

    Side-chain diagram showing CH₂–CH₂–C(=O)–OH from the Cα attachment marker.

    Which amino acid has this side chain?

    Answer

    Glutamate — side chain: Cα–CH₂–CH₂–C(=O)–OH.

  89. Card 89

    Question

    Histidine → one-letter code

    Answer

    H

  90. Card 90

    Question

    Side-chain diagram showing CH bonded to two CH₃ branches from the Cα attachment marker.

    Which amino acid has this side chain?

    Answer

    Valine — side chain: Cα–CH(CH₃)₂.

  91. Card 91

    Question

    Serine → three-letter code

    Answer

    Ser

  92. Card 92

    Question

    Asn → amino-acid name

    Answer

    Asparagine

  93. Card 93

    Question

    F → amino-acid name

    Answer

    Phenylalanine

  94. Card 94

    Question

    Lysine → draw or recall the side chain

    Answer

    Side-chain diagram showing (CH₂)₄–NH₂ from the Cα attachment marker.

    Side chain: Cα–(CH₂)₄–NH₂.

  95. Card 95

    Question

    Alanine → one-letter code

    Answer

    A

  96. Card 96

    Question

    Side-chain diagram showing CH with one CH₃ branch and one CH₂–CH₃ branch from the Cα attachment marker.

    Which amino acid has this side chain?

    Answer

    Isoleucine — side chain: Cα–CH(CH₃)–CH₂–CH₃.

  97. Card 97

    Question

    Cysteine → three-letter code

    Answer

    Cys

  98. Card 98

    Question

    Asp → amino-acid name

    Answer

    Aspartate

  99. Card 99

    Question

    Y → amino-acid name

    Answer

    Tyrosine

  100. Card 100

    Question

    Arginine → draw or recall the side chain

    Answer

    Side-chain diagram showing (CH₂)₃–NH–C(=NH)–NH₂ from the Cα attachment marker.

    Side chain: Cα–(CH₂)₃–NH–C(=NH)–NH₂.

  101. Card 101

    Question

    Ser → amino-acid name

    Answer

    Serine

  102. Card 102

    Question

    N → amino-acid name

    Answer

    Asparagine

  103. Card 103

    Question

    Phenylalanine → draw or recall the side chain

    Answer

    Side-chain diagram showing CH₂ joined to a six-membered ring with alternating double bonds from the Cα attachment marker.

    Side chain: Cα–CH₂–C₆H₅.

  104. Card 104

    Question

    Lys → amino-acid name

    Answer

    Lysine

  105. Card 105

    Question

    A → amino-acid name

    Answer

    Alanine

  106. Card 106

    Question

    Isoleucine → draw or recall the side chain

    Answer

    Side-chain diagram showing CH with one CH₃ branch and one CH₂–CH₃ branch from the Cα attachment marker.

    Side chain: Cα–CH(CH₃)–CH₂–CH₃.

  107. Card 107

    Question

    Cys → amino-acid name

    Answer

    Cysteine

  108. Card 108

    Question

    D → amino-acid name

    Answer

    Aspartate

  109. Card 109

    Question

    Tyrosine → draw or recall the side chain

    Answer

    Side-chain diagram showing CH₂ joined to a six-membered ring with an opposite OH group from the Cα attachment marker.

    Side chain: Cα–CH₂–C₆H₄–OH (para).

  110. Card 110

    Question

    Arg → amino-acid name

    Answer

    Arginine

  111. Card 111

    Question

    P → amino-acid name

    Answer

    Proline

  112. Card 112

    Question

    Leucine → draw or recall the side chain

    Answer

    Side-chain diagram showing CH₂–CH with two terminal CH₃ branches from the Cα attachment marker.

    Side chain: Cα–CH₂–CH(CH₃)₂.

  113. Card 113

    Question

    Thr → amino-acid name

    Answer

    Threonine

  114. Card 114

    Question

    Q → amino-acid name

    Answer

    Glutamine

  115. Card 115

    Question

    Tryptophan → draw or recall the side chain

    Answer

    Side-chain diagram showing the Cα attachment marker joined through CH₂ to position 3 of fused five- and six-membered rings containing NH.

    Side chain: Cα–CH₂–indol-3-yl.

  116. Card 116

    Question

    Met → amino-acid name

    Answer

    Methionine

  117. Card 117

    Question

    G → amino-acid name

    Answer

    Glycine

  118. Card 118

    Question

    Glutamate → draw or recall the side chain

    Answer

    Side-chain diagram showing CH₂–CH₂–C(=O)–OH from the Cα attachment marker.

    Side chain: Cα–CH₂–CH₂–C(=O)–OH.

  119. Card 119

    Question

    H → amino-acid name

    Answer

    Histidine

  120. Card 120

    Question

    Valine → draw or recall the side chain

    Answer

    Side-chain diagram showing CH bonded to two CH₃ branches from the Cα attachment marker.

    Side chain: Cα–CH(CH₃)₂.

Abstract molecular study scene with colorful ball-and-stick side-chain forms arranged around an open center.

120 cards

Amino Acid Flashcards: 20 Side-Chain Structures & Codes

Study this deck for free

Flashcards opens so you can start studying.