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Biomolecules (Y2,S1) > Amino Acids & Peptides > Flashcards

Amino Acids & Peptides Flashcards

1
Q

What do all AAs (excluding Pro) have in common structurally?

A
  1. An acidic carboxyl group connected to the alpha carbon
  2. A basic amino group connected to alpha carbon
  3. An alpha hydrogen connected to the alpha carbon
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2
Q

What is unique about the R group in Glycine

A

The fourth substituent (R group) is also a hydrogen. It’s the simplest AA.

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3
Q

What do neutral AAs have

A

One COOH & one NH2 group

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4
Q

What do acidic AAs have

A

Two COOH and one NH2 groups

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5
Q

What do basic AAs have

A

One COOH group and two NH2 groups

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6
Q

Which 3 AAs are basic

A
  1. Lysine (Lys)
  2. Arginine (Arg)
  3. Histidine (His)
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7
Q

Which 2 AAs are acidic

A
  1. Aspartic acid (Asp)
  2. Glutamic Acid (Glu)
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8
Q

What do AAs with non polar side chains not participate in

A

Hydrogen or ionic bonding

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9
Q

Why is Cysteine a special AA

A

The SH group of two cysteines can be oxidised to form a covalent cross link called a disulphide bond

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10
Q

Why is Glycine a special AA

A

It’s R group is a hydrogen molecule

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11
Q

Why is Proline a special AA

A

Its side chainand alpha amino N form a rigid ring structure. Proline is therefore often found at bends or turns in protein structure.

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12
Q

What is desmosine (elastin) formed from

A

4 Lysine residues

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13
Q

Ubiquitination

A
  • Ubiquitin (a protein) attaches to Lysine via an isopeptide bond
  • Mediates protein degradation (tidies AAs before degradation), signalling, trafficking
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14
Q

To which AAs does the process of methylation occur

A
  • Attachment of a methyl group to Lys/Arg
  • This regulates RNA processing, transcription, DNA damage repair
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15
Q

To which AAs does phosphorylation occur

A
  • Attachment of a phosphate group to Ser/Thr/Tyr residues
  • Done by kinases, reversible process
  • Regulates enzymatic activity
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16
Q

To which AAs does Glycosylation occur

A
  • Attachment of glycans (sugars?) to Asn/ Ser/ Thr/ Tyr residues
  • Involved in cell-cell interaction and recognition, protein folding and chaperone recruitment
17
Q

To which AAs does Acetylation occur

A
  • Attachment of an acetyl group to Lysine
  • Mediates protein-protein interaction
18
Q

What form do AAs exist as at low pH

A

They exist in a positively charged form (cation) at low pH

19
Q

What form do AAs exist as at high pH

A

They exist in a negatively charged form (anion) at high pH

20
Q

When the molecule has both a positive and negative charge, what does the AA exist as

A

The AA exists in zwitterion form (- carboxyl group & + amino group)

21
Q

What is the Isoelectric Point of an AA

A

The point when the net charge of the AA is zero.

22
Q

What happens to the AA at its isoelectric point

A
  1. AA is least soluble in water
  2. AA doesn’t migrate in electric field
23
Q

What AA can act as a buffer in two pH ranges

A

Glycine

24
Q

What type of reaction is involved in peptide bond formation

A

Dehydration/condensation reaction (requires ATP)

25
Q

Where to start when naming peptides

A

At the N-terminal (Amino Terminal)

26
Q

4 Functions of peptides

A
  1. Hormones & Pheromones: insulin, oxytocin
  2. Neuropeptides: substance p (pain mediator)
  3. Antibiotics: polymyxin B (for gram neg), bacitracin (for gram pos)
  4. Protection: e.g: toxins
27
Q

3 things proteins could be comprised of

A

Polypeptides & possibly:
1. Cofactors
2. Coenzymes
3. Prosthetic groups

28
Q

What differences does separation of proteins rely on

A
  • Charge
  • Size
  • Affinity for a ligand
  • Solubility
  • Hydrophobicity
  • Thermal Stability
29
Q

The 7 AAs with ionizable side groups

A
  1. Aspartic Acid
  2. Glutamic Acid
  3. Histidine
  4. Cysteine
  5. Tyrosine
  6. Lysine
  7. Arginine
30
Q

Which of the 7 have terminal alpha carboxyl group (3)

A
  1. Aspartic acid
  2. Glutamic acid
  3. Histidine
31
Q

Which of the 7 have terminal alpha amino group (4)

A
  1. Cysteine
  2. Tyrosine
  3. Lysine
  4. Arginine

Biomolecules (Y2,S1) (6 decks)

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