1.1 Amino Acids Found in Proteins [HY] Flashcards

1
Q

All AA’s are optically active/ have a chiral center except?

A

Glycine, which has a hydrogen atom as its R group, making it achiral

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2
Q

All AA’s have a S configuration except?

A

Cysteine, has an (R) absolute
configuration because the −CH2SH group has priority over the −COOH group

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3
Q

What affect does proline’s ring have on it?

A

That ring places notable constraints on the flexibility of
proline, limiting where it can appear in a protein and can have significant effects on proline’s role in secondary structure.

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4
Q

Why are the polar AA’s polar?

A

B/c of the OH side chains, and therefore able to participate in hydrogen bonding.

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5
Q

Why is Sulfur on cysteine more likely to be oxidized?

A
  • sulfur is larger than oxygen, the S−H bond is longer and weaker than the O−H bond
  • Oxygen is more electronegative than Sulfur
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6
Q

What is physiological pH?

A

7.4

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7
Q

How do most acids exist in cells?

A

In the deprotonated form

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8
Q

Why are positive AA’s positive?

A

have side chains that have positively charged nitrogen atoms.

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9
Q

Which AA’s are hydrophobic?

A
  • A, I, L, V, F
  • Most likely in interior of proteins
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10
Q

Which AA’s are hydrophilic?

A
  • All positive AA’s (H, R, K)
  • Anions of D & E (aspartate, glutamate)
  • Amides: N & Q
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11
Q

Which AA’s are on the surface of proteins?

A
  • AA’s with charged side chains
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12
Q

What is notation for substitution?

A
  • [Letter of initial AA] [AA #] [Letter of final AA]
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