SURVIVAL MODE β’ 1-HOUR READ
𧬠Amino Acid Survival Sheet
The absolute bare minimum you need to pass. Memorize this page.
1. The Structure (Draw it or Die)
- General Formula: Ξ±-Carbon + Carboxyl (COOH) + Amino (NHβ) + H + R-Group.
- The Exception: Proline (Imino acid, NH in ring).
- Number: 20 Standard. 21st = Selenocysteine (Encoded by Stop Codon UGA).
2. Classification (The Lists You Must Vomit)
Nutritional
-
TV TILL PM
(Essential: Thr, Val, Trp, Ile, Lys, Leu, Phe, Met) - Semi-Essential: Arginine (Growing kids).
Metabolic
- Ketogenic (The "L"s): Leucine & Lysine.
- Mixed: PhTTI (Phe, Tyr, Trp, Ile).
- Branched Chain (BCAA): Val, Leu, Ile. (Muscle only!)
3. Chemical Groups & Rings
| Group/Ring | Amino Acids | Notes |
|---|---|---|
| Hydroxyl (-OH) | Ser, Thr, Tyr | [cite_start]Site of Phosphorylation [cite: 139] |
| Sulfur | Cys, Met | Cys forms Disulfide bonds. Met is Start codon. |
| Basic (+) | His, Arg, Lys | Positive at pH 7.4 |
| Indole Ring | Tryptophan | Largest ring. |
| Imidazole Ring | Histidine | Physiological Buffer. |
| Guanido Group | Arginine | Most Basic. |
4. Properties & Exam Traps
Definitions
- Amphoteric: Acts as Acid & Base.
- Zwitterion: Net Charge = 0. No migration.
- IEP: pH where AA is Zwitterion. Precipitates here.
- Peptide Bond: Rigid, Planar, Partial Double Bond.
The "Gotcha" Points
- Glycine: Smallest. Optically Inactive.
- Proline: Helix Breaker. Yellow with Ninhydrin.
- Cystine: 2 Cysteines + Disulfide bridge.
- Histidine: Best buffer (pKa 6.0 β Blood 7.4).
5. Colors & Modifications
Color Reactions
- π£ Ninhydrin: Purple (All) vs Yellow (Proline).
- π΄ Sakaguchi: Red (Arginine).
- π΄ Millonβs: Red (Tyrosine).
- π£ Hopkins-Cole: Purple Ring (Tryptophan).
Modified AA
- Hydroxyproline: Collagen. Requires Vit C. (Deficiency = Scurvy).
- Ξ³-Carboxyglutamate: Clotting. Requires Vit K.
π Reality Check: Keyword Matching
- If you see "Maple Syrup Urine" β Answer is Branched Chain AA.
- If you see "Scurvy" β Answer is Proline Hydroxylation.
- If you see "Nitric Oxide" β Answer is Arginine.