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BCC > Proteins > Flashcards

Proteins Flashcards

1
Q

What are the characteristics of an endergonic reaction?

A
  • Non spontaneous reaction.
  • Free energy is absorbed.
  • Change in G > 0.
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2
Q

What is meant by reasonance within an amino acid?

A

Partial double bond character between carbonyl carbon and nitrogen.

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3
Q

What is the Phi angle in an amino acid?

A

Angle between alpha carbon and nitrogen.

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4
Q

What is the Psi angle in an amino acid?

A

Angle between alpha carbon and carbon.

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5
Q

Number of ligands, porphyrin ring.

What are the characteristics of a deoxyhaemoglobin molecule?

A
  • Fe2+ binds 5 ligands and has larger atomic radius.
  • Fe2+ does not fit in plane of porphyrin ring.
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6
Q

What can a spectrophotometer be used to measure?

A

A pigment’s ability to absorb various wavelengths of light.

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7
Q

What does a ligand-binding curve display?

A

Plot of fractional saturation (Y) against concentration of ligand (X).
Forms a hyperbolic curve.

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8
Q

What condition do buffers function best under?

A

Within 1 pH unit of their pKa

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9
Q

What are the properties of an alpha helix?

A
  • Normally right handed coil.
  • tightly packed
  • Side chains point out.
  • Every carbonyl oxygen forms a hydrogen bond with amide hydrogen 1+4.
  • 3.6 residues per turn.
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10
Q

Describe the properties of a beta sheet.

A
  • Hydrogen bonds between N and O of adjacent beta strands
  • Can be parallel or anti-parallel or mixed
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11
Q

What are reverse turns, where are they found?

A
  • Found linking beta strands.
  • Used to change direction.
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12
Q

What is the function of coiled coils?

A

To minimise exposure of hydrophobic amino acid side chains to aqueous environment.

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13
Q

Describe the structure of the collagen triple helix.

A
  • 3 polypeptide chains.
  • Highly conserved sequences.
  • Every 3rd residue is glycine - only residue small enough.
  • Lots of proline so conformationally restricted.
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14
Q

What are the 2 structural forms of haemoglobin?

A
  • Deoxyhemoglobin = tense form = low affinity for oxygen.
  • Oxyhemoglobin = relaxed form = high affinity for oxygen.
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15
Q

What does the gradient of a Hill plot depict?

A

= 1 (no co-operativity)
>1 positive co-operativity

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16
Q

What is the concerted model for co-operativity?

A

when [O2] is low = T state favoured
when [O2] is high = R state favoured.
Protein will transition from T to R state as O2 concentration increases.

17
Q

What is the effect of 2,3 biphosphoglycerate (2,3-BPG) on haemoglobin?

A
  • Binds more tightly to deoxy-hb (T) than oxy-Hb (R)
  • BPG binds to and stabilises deoxy-Hb and so increases the P50.
18
Q

Explain the occurrance of Sickle Cell Anaemia.

A
  • Substitution mutation of glutamate to valine.
  • New hydrophobic interaction between neighbouring Hb’s.
  • Forms fibrous aggregates.
  • Distort red blood cells to sickle shape.
    (reduces half life of red blood cells so selective pressure towards as resistant to malaria).
19
Q

What do they separate based on?

What are the 4 types of column chromatography?

A
  • Gel fitration (size).
  • Ion exchange (charge).
  • Hydrophobic interaction
  • Affinity Chromatography (specific protein interactions).
20
Q

How does ion exchange chromatography separate proteins?

A
  • Based on charge.
  • Solution passed through a matrix containing charged media, proteins will bind depending on charge.
21
Q

What are 2 common examples of IEX media?

A
  • DEAE Cellulose (positive charge).
  • CM Cellulose (negative charge).
22
Q

What is a native protein?

A

Protein in its functional folded conformation.

23
Q

What is screw sense?

A

Rotation of an alpha helix with respect to its axis.

24
Q

What effects do competitive inhibitors have on Lineweaver-Burk plots?

A

No change in Vmax, KM increases.

25
Q

What is the p50?

A

It is the KD when talking about concentration of O2.
Dissociation constant, [O2] required to occupy 50% of binding sites.

26
Q

What is the p50 for human myoglobin?

A

Approx. 2 torr.

27
Q

What is the p50 for human haemoglobin?

A

Approx. 26 torr

lower affinity than myoglobin

28
Q

How much energy is released by each mole of ATP?

A

30kJ

29
Q

How do you convert units of kJ to kcal?

A

Divide by 4.2

30
Q

What is the concentration of water?

A

55.6mol per litre

31
Q

What is a polyprotic acid?

A

A molecule that can undergo more than one ionisation, giving it multiple pKa values.

BCC (6 decks)

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