4. Proteins Flashcards

1
Q

Rotation of bonds between amino acids

A

-Limited rotation around N-C=O as the electrons are shared across (resonance)
-bonds around α-carbon can rotate

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2
Q

Types of diagrams showing protiens

A

-space-filling
-ball and stick
-backbone
-ribbon

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3
Q

Collagen

A

Repeating unit of Gly-X-Y, and ringed stucture of proline and hydroxyproline put additional restraint on polypeptide chains

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4
Q

3 possible non-polypeptide components in proteins

A

-heme group
-metal ions
-glycosylation (saccharides)

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5
Q

When are proteins “native”?

A

-under physiological condition
-most stable structure
- biologically active structure.

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6
Q

When are proteins denatured?

A

-Extreme temp breaks non-covalent bonds
-pH changes, ionization state of side-chains change; disrupts of electrostatic and H bonds
-Denaturation reagents e.g. ionic detergents (SDS), hydrogen bonding agents (urea), metal chelators (EDTA) [pull metal ions out to form bonds]
-Reducing agent (dithiothreitol) breaks disulphide bonds
-biologically inactive

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7
Q

Structures lost after folding

A
  1. Preproinsulin–> lose signal sequence= proinsulin
  2. Di-sulfide bonds formed in the proinsulin
  3. C-peptide bond is lost and leaves a mature insulin, holding the chains by the bonds
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8
Q

Driving force of folded proteins

A

Unfolded proteins have:
-solvation of hydrophobic domains = neither entropy or enthalpy are favoured

Folded proteins have:
-stronger intermolecular forces as amino acids are in closer prximity = enthalpy favoured
-hydrophobic effect = entrophy favoured

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9
Q

Levinthal paradox

A

-the large number of degree of freedom in the unfolded protein means the number of possible conformations is astronomical

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10
Q

Conformational entropy in protein folding

A

-Unfolded protein=high entropy
-formation of 1st interaction = large loss in conformational entropy
-subsequent interactions occur and entropy decreases until no further loss of

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11
Q

Chaperones

A

Bind to non-native proteins, assist in protein folding

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12
Q

Prion

A

-a protein infective agent
-caused by mis-folding of a protein
-causes mis-folding of its natural counterpart which goes on to do the same; chain reaction

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