Proteins 1 Flashcards

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1
Q

What occurs during protein synthesis?

A
  • DNA transcribed to RNA

- RNA translated to protein

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2
Q

Codon

A

Chain of three bases which code for an amino acid

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3
Q

What is a codon defined by?

A

The initial nucleotide from which translation starts

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4
Q

What is the basic structure of an amino acid?

A

Central carbon with 4 bonds:

  • amino group
  • variable side chain
  • carboxylic acid group
  • hydrogen
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5
Q

What are the different types of amino acids?

A
Aliphatic
Aromatic
Sulphur containing
Basic
Uncharged polar
Acidic
Other
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6
Q

What is a peptide bond?

A

Covalent bond between a carboxylic acid and amine group

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7
Q

Where does the formation of peptide bonds occur?

A

Within a ribosome in during translation

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8
Q

What is a polypeptide chain?

A

A chain of two or more amino acids covalently bonded

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9
Q

What is the primary structure of a protein?

A

The sequence of amino acids in a polypeptide chain

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10
Q

What is the source of versatility in a proteins structure and function?

A

The primary structure

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11
Q

What is the secondary structure of a protein?

A

The spatial arrangement of amino acid residues that are near each other in linear sequence

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12
Q

What two structures are involved in secondary structure?

A

Alpha Helix

B Pleated Sheet

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13
Q

How is the alpha helix structure held in place?

A

By hydrogen bonds between every N-H group and the O2 of the C=O group in the next turn of the helix

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14
Q

How is the beta pleated sheet structure held in place?

A

Held together by hydrogen bonds between the amide groups of linear polypeptide chains

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15
Q

What is the tertiary structure of a protein?

A

The spatial arrangement of amino acid residues that are far apart in a linear sequence

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16
Q

What forces are involved in the tertiary structure of a protein?

A
Van der Waals
Ionic interactions
Hydrogen bonds
Disulphide bridges
Hydrophobic interactions
17
Q

When do ionic interactions occur?

A

Between 2 close, oppositely charged R groups

18
Q

What are Van der Waals?

A
  • Non-specific, weak attractions between atoms 0.3-0.4 nm apart
  • They are individually weak but in a folded protein structure, a large number exist- thereby stabilising the structure
19
Q

What are hydrogen bonds?

A
  • Similar to Van der Waals but are stronger and permanent

- Occur when H is bonded to either O, N or F and a lone pair of electrons are present

20
Q

Name 2 substances that hydrogen bonding takes place in?

A

Water

Ammonia

21
Q

What are hydrophobic interactions?

A

Intra-polypeptide interactions which occur in an environment within proteins from which water is excluded

22
Q

Where are the hydrophobic R groups in globular water-soluble proteins?

A

Inside of the protein

23
Q

What makes a protein water soluble?

A

Hydrophilic R groups on the outside hydrogen bonding to water

24
Q

What are disulphide bridges?

A
  • Strong covalent bonds between two cysteine residues.
  • Common in extra-cellular proteins
  • Can occur between as well as within a polypeptide
25
Q

What is the quaternary structure of a protein?

A

Refers to the spatial arrangement of individual polypeptide chains in a multi-subunit protein

26
Q

What does the denaturation of proteins involve?

A

The disruption and possible destruction of both secondary and tertiary structures

27
Q

Why does the primary structure remain the same after denaturation?

A

Denaturation reactions are not strong enough to break the peptide bonds

28
Q

What can cause denaturation?

A
  • Acids
  • Heat
  • Solvents (ethanol, methanol)
  • Cross linking reagents (formaldehyde)
  • Chaotropic agents (urea)
  • Disulphide bond reducers (2 mercaptoethanol)
29
Q

What are the effects of denaturation?

A
  • Decreased solubility
  • Altered water binding capacity
  • Loss of biological activity
  • Improved digestibility
30
Q

What are peptidases responsible for?

A

Cleavage of peptide bonds

31
Q

What are endopeptidases responsible for?

A

Cleavage of internal bonds

32
Q

What are exopeptidases responsible for?

A

Cleavage of one amino acid at a time

33
Q

What are carboxypeptidases responsible for?

A

Cleavage at -COOH terminal

34
Q

What are aminopeptidases responsible for?

A

Cleavage at -NH2 terminal