Module 3 Flashcards

1
Q

what 2 forms are amino acids found in?

A

L and D forms

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2
Q

what form of amino acid are found in proteins?

A

L stereoisomers

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3
Q

are all amino acids diprotic?

A

yes

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4
Q

what is the isoelectric point?

A

net charge on molecule equals zero

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5
Q

what charge will the amino acid have if the pH is below the isoelectric point?

A

net positive charge

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6
Q

what charge will the amino acid have if the pH is above the isoelectric point?

A

net negative charge

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7
Q

what is an amino acid?

A

a peptide of 3 residues

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8
Q

what does simplicity mean in regards to amino acids?

A

1 type of reaction for polymerization + degradation

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9
Q

what hands do L + D isomers represent?

A

L = Left hand
D= Right hand

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10
Q

what are the 5 side groups of amino acids?

A
  1. non-polar
  2. aromatic
  3. polar, uncharged
  4. polar, positively charged
  5. polar, negatively charged
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11
Q

what side chains so non-polar amino acids have?

A

mainly hydrocarbons

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12
Q

what amino acids have sulfur groups for side chains?

A

methionine & cysteine

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13
Q

what is the smallest amino acid?

A

Glycine

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14
Q

what amino acid is usually in combo with glycine?

A

proline

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15
Q

what amino acid can also be considered an aromatic?

A

Histidine

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16
Q

what is post translational modification?

A

when some amino acids can be covalently modified after their incorporation into a protein (often reversible)

17
Q

what are disulfide bonds?

A

forms through oxidation of sulfhydryl groups of 2 cysteine resiudes to form a covalent linkage

18
Q

can disulfide bonds be both intermolecular & intramolecular?

A

yes

19
Q

what amino acid serves as a proton acceptor and donor?

A

Histidine

20
Q

what does diprotic mean?

A

has 2 buffering regions & can yield 2 H+

21
Q

what does triprotic mean?

A

has 3 buffering regions -> have ionizable groups in side chains

22
Q

what is a zwitterion?

A

a molecule that has a positively charged & negatively charged group

23
Q

what is the charge of the zwitterion above the pKa?

A

negative

24
Q

what is the charge of the zwitterion below the pKa?

A

positive

25
Q

between what range will an amino acid be a zwitterion?

A

between a pH of 2-10

26
Q

isoelectric point / neutral zone is calculated by:

A

pKa1 + pKa2 / 2

27
Q

how to calculate the average of pKa values?

A

PI= pKa + pKa2 / 2

28
Q

what does PI represent?

A

isoelectric point / average of pKa values

29
Q

what amino acid forms sulfide bonds?

A

cysteine

30
Q

why does histidine have a 0 or + 1 charge?

A

bc of the imidazole group