AAs and Buffers Flashcards

midterm 1

1
Q

what is an amino acid?

A

a compound consisting of a central carbon atom, attached to an amino group, a carboxyl group, a side chain (R group), and an H atom

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2
Q

oligopeptide

A

few amino acids joined together

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3
Q

polypeptide

A

many amino acids joined together ( 4 or more)

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4
Q

Protein

A

a macromolecule that consists of one or more polypeptide chains (50 AA’s or greater)

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5
Q

how many common AA’s are there?

A

20

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6
Q

what are all proteins composed of?

A

20 “standard” AA’s, which are those for which at least one codon exists in the genetic code

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7
Q

what are common AA’s known as?

A

alpha amino acids

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8
Q

4 classifications of AA’s based off R groups

A
  1. Non-polar (hydrophobic)
  2. Polar neutral (unionized)
  3. Polar negatively charged (acidic)
  4. Polar positively charged (basic)
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9
Q

unique AA’s

A

Glycine: has two H groups
Proline: has a secondary amino group (rather than a primary amino group)

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10
Q

what is an essential amino acid?

A

an amino acid that must be obtained through diet; can’t be synthesized from other precursors (ex. Histidine)

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11
Q

AA configuration

A

alpha carbon ( a chiral center)
D or L configuration (all biological proteins are L-stereoisomers)

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12
Q

Electrolytes

A

are substances that dissociate in water into a cation (+ charged ion) and anion (- charged ion)

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13
Q

types of electrolytes

A

strong electrolytes: completely dissociate in solution (ex. strong acids/bases, salts)
weak electrolytes: partially dissociate in solution (ex. weak acid/bases)
non-electrolytes: dissolve as molecules in solution (ex. sugars/alcohols)

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14
Q

Bronsted-Lowry theory

A

acids: compounds that donate protons (H+)
bases: compounds that accept protons (H+)

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15
Q

Lewis theory

A

acids: electron pair acceptors
bases: electron pair donors

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16
Q

pH equation

A

pH= -log [H+]

17
Q

Keq/Ka equation and purpose

A

Keq (Ka)= [H+][A-]/[HA]
measure strength of an acid

18
Q

Ka and H+ relationship

A

larger Ka= greater # of H+ ions released, which means a stronger acid

19
Q

what is the Ka constant?

A

acid dissociation constant

20
Q

pKa equation

A

pKa= -logKa

21
Q

pKa and H+ relationship

A

lower pKa= greater # of H+ ions released, which means a stronger acid

22
Q

pKa difference from pH

A

pH is conc. dependent, pKa is constant for each type of molecule

23
Q

Henderson-Hasselbalch equation

A

pH=pKa + log [A-]/[HA]
[A-]= conj. base
[HA]= weak acid

24
Q

Henderson-Hasselbalch purpose

A

used to to tell if [A-] or [HA] is dominant
allows us to predict the relative amounts of protonated vs unprotonated species in a solution

25
AA's at physiologic pH
amino group is protonated carboxylic acid group is unprotonated due to the pKa of the side groups
26
How are AA's amphoteric molecules?
carboxyl groups= weakly acidic amino groups= weakly basic r groups= ionizable
27
Zwitterion molecules
molecules which bear plus & minus charges simultaneously (diploar ions)
28
when are AA's Zwitterions?
at physiological pH
29
Buffers
are solutions which resist a change in pH when acids or bases are added is a mixture of either HA/A- or HB+/B
30
example of how a buffer works
if acid is added, A- can neutralize (->HA) if base is added, HA can neutralize (-> A-)
31
maximal buffering capacity occurs...
when pH=pKa (can buffer effectively within +/- 1 ph=pKa difference
32
Henderson-Hasselbalch equation for Buffers
if pH of the solution is less than pKa of the buffer, [HA]>[A-] (solution is mostly protonated) if pH of the solution is more than pKa of the buffer, [HA]<[A-] (solution is mostly unprotonated)
33
MOA of Pilocaprine HCl opthalamic solution
primary MOA: pupil constriction secondary MOA: ciliary muscle contracts
34
Pilocarpine
-unstable at physiologic pH -stored at pH=4, pKa=6.6, so pH
35
Drug absorption
- oral drugs must cross stomach/intestinal epithelium for absorption into the blood (uncharged form) - so best absorbed at pH which results in neutral molecule (HA or B)
36
Renal system relationship to drug excretion
-weakly acidic/basic drugs are filtered at the glomeruli for excretion -urine pH determines the amount of drug excretion/retention
37
urine pH
alkaline urine= weakly acidic drugs excreted more rapidly acidic urine= weakly basic drugs excreted more rapidly