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Chemistry 101 COPY > Amino Acids and Isoelectric Points > Flashcards

Amino Acids and Isoelectric Points Flashcards

1
Q

What do all amino acids have in common?

A

All amino acids have a common part

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2
Q

How do all amino acids differ?

A

All amino acids have an individual feature

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3
Q

What controls the function of an amino acid?

A

Its structure

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4
Q

Why are all proteins chemically similar?

A

As they are all made up of amino acids

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5
Q

Describe the structure of an amino acid

A

It is formed of a chiral centre, with one carboxylic acid chain, one amine chain, one hydrogen and one R branch

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6
Q

What do amino acids vary in?

A

The side (R) chain

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7
Q

How many categories of amino acids are there?

A

5

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8
Q

What are the 5 categories of amino acids based on?

A

The side chain

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9
Q

What are the 5 categories of amino acids?

A

Non-Polar

Polar uncharged

Acidic

Basic

Aromatic

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10
Q

What do non-polar amino acids contain?

A

An alkyl chain

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11
Q

What is an example of a group that would be attached to a polar uncharged amino acid?

A

A hydroxyl (alcohol) group

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12
Q

What is an example of a group that would be attached to an acidic amino acid?

A

Another carboxylic acid

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13
Q

What is an example of a group that would be attached to a basic amino acid?

A

Another amine

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14
Q

What do aromatic amino acids contain?

A

Aromatic rings

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15
Q

Amino Acids are zwitterionic. What does this mean?

A

They contain both an acidic and a basic group

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16
Q

What is a zwitterion?

A

A neutral molecule which contains both a positive and a negative charge

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17
Q

What can zwitterions also be considered?

A

Salts

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18
Q

What properties must zwitterions have if they are salts?

A

They are water soluble and have high melting points

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19
Q

What does the true structure of an amino acid depend on?

A

The pH of the solution/environment that it is in and hence the pKa of each group

20
Q

What is pKa?

A

The equilibrium constant

21
Q

What can be said about the equilibrium constants of every acidic or basic group?

A

For every acidic or basic group in a molecule there is an equilibrium constant (pKa). Each equilibrium occurs in a stepwise fashion.

22
Q

Draw the equilibrium mechanism of an amino acid

A
23
Q

What can we conclude if pH < pKa?

A

The functional group is protonated

24
Q

What can we conclude if pH > pKa?

A

The functional group has lost its proton

25
Q

What are Heterocyclic Amines?

A

Aromatic Rings with Nitrogen

26
Q

What is Pyrrole?

A

A five-membered aromatic heterocycle

27
Q

Draw the structure of pyrrole

A
28
Q

What is pyridine?

A

A six membered aromatic heterocycle

29
Q

Is pyrrole basic?

A

No

30
Q

Why is pyrrole not basic?

A

Its nitrogen lone pair is involved in the pi orbital system

31
Q

What occurs if the nitrogen in pyrrole donates its lone pair to accept a proton?

A

Its aromaticity is lost, which is energetically unfavoured

32
Q

Why is pyridine basic?

A

Its lone pair isn’t involved in the conjugated pi orbital system, so the lone pair can donate electrons to an acid

33
Q

Is pyridine basic?

A

Yes

34
Q

What is a general rule for determining if a heterocyclic amine is basic or not?

A

Anything with an NH group tends not to be basic whereas anything with an N tends to be basic

35
Q

What is an imidazole ring?

A

A five-membered heterocyclic amine that has an N (basic) group and an NH (non-basic) group

36
Q

What is the Isoelectric point, pI?

A

The pH at which the amino acid exists as a neutral dipolar zwitterion

37
Q

What can be said about the pI of an amino acid?

A

Each amino acid has its own pI which depends on its structure

38
Q

How do you determine the pI of an amino acid?

A

By finding the average of the two acid-dissociation constants that involve the neutral zwitterion

39
Q

What can be said when pI = pH?

A

You have 100% of the formation with net charge = 0

40
Q

Does a molecule with a net charge of +1 have a high pH or low pH?

A

A low pH

41
Q

Does a molecule with a net charge of -1 have a high pH or low pH?

A

A high pH

42
Q

What is electrophoresis?

A

A method of separating compounds based on their electric charges. It can be used to separate and identify mixtures of amino acids and proteins.

43
Q

What are the three steps to perform electrophoresis?

A

Place amino acids on gel

Connect the electrodes (positive and negative end)

Amino acids move based on charge

44
Q

How will a negatively-charged amino acid behave in electrophoresis?

A

A negatively charged amino acid has a low pI and moves towards the positive electrode

45
Q

How does a negatively-charged amino acid behave in electrophoresis?

A

A negatively-charged amino acid has a low pI and moves towards the positive electrode

Chemistry 101 COPY (32 decks)

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