amino acids

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Author:
chiflavored
ID:
7938
Filename:
amino acids
Updated:
2010-02-24 02:31:12
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amino acids biochemistry
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Description:
amino acids properties, functions, and molecular structures
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  1. amino acid (general functions and characteristics)
    • - the building block molecules: structural units of proteins
    • -protein's struc and func are determined by the struc + properties of its AA's
    • - contains a carboxylic acid w/ an amino grp
    • - 20 commonly found in proteins (standard/ common/ alpha AA's)
    • -almost all have an asymetric alpha-c except lysine
    • - all diff substituents connected to that C
    • - have acid/base properties
  2. what does "alpha- AA's" mean?
    • -carbonyl + amino grp are bonded to alpha-carbon
  3. alpha C is a chiral center because:
    • 1. optically active: rotates plane of plane polarized light right or left
    • 2. 2 possible configurations exist:
    • -spatial (3D) arrangement of grps about chiral centers, forming stereoisomers (L/D)
    • - also known as enantionmers: non-super imposable mirror images
  4. AA's with non-polar, hydrophobic, aliphatic (non- benzene- like) R grps
    • - R grps cluster together in interior of protein
    • - shielded from H20
    • - hydrophobic interactions
    • list:
    • glycine
    • L-alanine
    • L-proline
    • L-valine
    • L-leucine
    • L-isoleucine
    • L-methionine
  5. Glycine (Gly)


    • - branched H grp
    • - little hydrophobic character
    • - b/c of 2 H's: no asymetric carbon, not chiral
  6. L-Alanine (Ala)


    • -branched methyl grp
    • -diphatic hydrocarbon
  7. L-proline (Pro)
    • L-Proline
    • hydroxyproline

    • - only AA with N linked to C
    • - whenever it appears there is a bend in the 3-D structure of protein
    • - found in lrg amnts in collagen (primary protein in connective tissues)
    • - need to be converted by switching one of H2 grps to hydroxy grp
    • - restricts geometry of polypep
    • - abrupt change in direction of polypep chain
  8. L-valine (Val)


    -branched aliphatic grp: CHCH3CH3
  9. L-Leucine (Leu)


    -branched aliphatic after an attachment of CH2: CHCH3CH3
  10. L-Isoleucine (Ile)


    • -branched aliphatic:CH3CHCH2CH3
    • - 2 chiral centers
  11. L-methionine (Met)


    -branched methyl thio ether that is non polar
  12. AA's with aromatic R grps
    • - relatively nonpolar + hydrophobic
    • - can participate in hydrophobic interactions

    • list:
    • L-Phenylalanine
    • L-Tyrosine
    • L-Trytophan
  13. L-Phenylalanine (Phe)


    -branched benzyl grp
  14. L-Tyrosine (Tyr)


    -branched polar grp
  15. L-Tryptophan (Trp)


    • -branched polar grp - indole grp
    • - aromatic heterocyclic
    • - NH- polar grp
  16. AA's w/ polar uncharged R grps
    - more soluble in H2O than nonpolar AA's

    • list:
    • L-Serine
    • L-Threonine
    • L-Cysteine
    • L-Asparagine
    • L- Glutamine
  17. L-Serine (Ser)


    - branched Beta-hydroxyl grp
  18. L-Threonine (Thr)


    • -branched hydroxyl grp
    • - 2 chiral centers
  19. L-Cysteine (Cys)


    • - SH: can form weak H-bonds
    • sulfhydryl grp (thiol grp)
  20. What is cystine?
    • (Cys-Cys)
    • - the sulfhydryl bonds to one another to form S-S bridge between 2 cysteine = disulfide bond
    • - has special role in struc. of some proteins
    • 1. Intrachain of disulfide bond
    • links different regions of polypep covalently
    • stabilizes the struc.
    • 2. Interchain of disulfide bond
    • links different polypep to ea. other
  21. L-Asparagine (Asn)


    • - branched amide grp
    • - NH2- not charge b/c protons not avail. to share w/ H
  22. L-Glutamine (Gln)


    - branched amide grp
  23. AA's w/ positively charged R grps
    contain nitrogenous base that's protnated at pH 7.0

    • list:
    • L-Lysine
    • L-Arginine
    • L- Histidine
  24. L-Lysine (Lys)
    • -branched (CH2)4NH3
    • -NH3: epsilon- amino grp
  25. L-Arginine (Arg)


    -branched guanidino grp: NHC(NH2)2
  26. L-Histidine (His)


    • -this mol represents 91% in soln. at pH 7.0 (net chrg = 0)
    • - the other 9% is the other struc, which is protonated (net chrg = +1)
  27. AA's w/ negatively charged R grps
    • list:
    • L-Aspartate
    • L-Glutamate
  28. L-Aspartate (Asp)
    • -branched: CH2COO-
    • - COO- : Beta carboxyl grp
    • -L-aspartic acid
  29. L- Glutamate (Glu)
    • - branched: CH2CH2COO-
    • - COO- : alpha carboxyl grp
    • - L-glutamic acid

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