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Chemistry > Amino Acids & Chirality > Flashcards

Amino Acids & Chirality Flashcards

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1
Q

What is the general formula of an amino acid?

A

RCH(NH2)COOH

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2
Q

What are alpha - amino acids?

A

Amino group and carboxylic acid group are attached to the same carbon atom.

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3
Q

Amino acids are BIFUNCTIONAL. Explain what this means.

A

They have two functional groups present:

  • NH2 (base)
  • COOH (acid)
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4
Q

What is an acid?

A

A proton donor (gives a H+ ion)

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5
Q

What is a base?

A

A proton acceptor.

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6
Q

What is a zwitterion?

A

An ‘internal’ salt of an amino acid, in which the -COOH group donates a proton to the -NH2 group forming NH3+ & COO-.

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7
Q

What effect does a zwitterion have on the properties of an amino acid?

A

Ionic charges increase the attractive forces between the amino acid in the solid, so raising the melting point significantly.

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8
Q

What is formed when amino acids react with acids or bases?

A

A salt.

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9
Q

At a low pH, what is the charge of a zwitterion?

A

Positive.

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10
Q

At a high pH, what is the charge of a zwitterion?

A

Negative.

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11
Q

What is the definition of an isoelectric point?

A

When the solution of an amino acid has the maximum concentration of zwitterions.

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12
Q

How are peptide bonds formed?

A

Via condensation reactions (condensation polymerisation).

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13
Q

How an you represent a peptide link?

A

-CONH- or -NHCO-

-C=O -N-H
| |
N-H- -C=O

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14
Q

What happens if you repeat condensation reactions many times?

A

You get polypeptides or proteins.

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15
Q

What is hydrolysis?

A

The process of breaking the peptide link by a reaction with water.

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16
Q

What is the catalyst for hydrolysis (living and lab)?

A

They are catalysed by enzymes in living organisms.

In the lab, they are catalysed by acids or alkalis.

17
Q

What does an a-amino acid and an excess alkali react to form?

A

Carboxylate salts e.g. In case of Sodium, on COOH group COO-Na+ formed.

18
Q

What is stereoisomerism?

A

When atoms have the same order of bonds and atoms but a different spatial arrangement of atoms.

19
Q

What is the difference between E and Z isomerism?

A

E - opposite sides

Z - same side

20
Q

What are optical isomers?

A

Molecules that are non-superimposable mirror images of each other.

21
Q

What is a chiral centre?

A

A (carbon) atom in a molecule attached to 4 different groups.

22
Q

How many optical isomers are formed and what are the differences between them?

A

2:
• 1 rotates plane polarised light to left
• the 2nd rotates plane polarised light to right

23
Q

What is a equal split of enantiomers called?

A

A racemic mixture.

24
Q

What can’t a racemic mixture do?

A

Deflect polarised light.

25
Q

How do drugs work?

A

Drugs work by binding to enzymes active sites or cell surface receptors causing a chemical reaction.

Drugs must have the correct shape to fit into binding site - only one enantiomer will do.

The other enantiomer may bind to another active site and have no effect, or cause a harmful side effect.

26
Q

Why would pharmaceutical companies make drugs with only one optical isomer?

A
  • smaller doses can be used (only 1/2 amount)
  • fewer side effects
  • drug is more efficient and effective
  • reduces risk of litigation
  • this increases costs as optical isomers are difficult and expensive to seperate
27
Q

What methods can you use to produce single enantiomers?

A
  • using natural enzymes or bacteria
  • using naturally occurring single optical isomers compounds as the starting material
  • using chemical chiral synthesis
  • using chiral catalysts - reusable but $$$
28
Q

Describe the properties of proteins.

A
  • polypeptides with high molecular mass
  • chains can be lined up with each other
  • the C=O and N-H bonds are polar due to difference in electronegativity
  • hydrogen bonding exists between chains
29
Q

What are the reagents and conditions for a hydrolysis reaction?

A

Reagents: aqueous acid (H2SO4)/ alkali (NaOH)
Conditions: warm/hot, reflux

30
Q

When you are given a chemical with chloride and you’re asked for a reagent that would make it turn to an amino acid, what is this reagent?

A

(ethanolic) ammonia

Chemistry (5 decks)

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