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Bioc 405 > Myoglobin & Hemoglobin > Flashcards

Myoglobin & Hemoglobin Flashcards

1
Q

True or False: myoglobin has a heme group with a Fe(III) ion in the center

A

False: the heme group has a Fe(II) ion in the center

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2
Q

Which form is the “T-state”?

A

Deoxy-Hb

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3
Q

Which form is the “R-state”?

A

Oxy-Hb

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4
Q

Between T and R states, which has a lower free energy?

A

T-state, the free energy is lower bc of the absence of oxygen.

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5
Q

What is the shape of the oxygen-binding curve of myoglobin?

A

Hyperbolic

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6
Q

What is the shape of the oxygen-binding curve of hemoglobin?

A

Sigmoidal (S-shape)

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7
Q

What does a hill coefficient of 1 mean?

A

No cooperativity

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8
Q

What does a hill coefficient of >1 mean?

A

There is cooperativity (the higher the hill coefficient, the steeper the curve)

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9
Q

Why would myoglobin be a poor oxygen transporter?

A

It binds oxygen really tightly so it wouldn’t let it go into the tissues when needed

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10
Q

In the O2 bound state of myoglobin, what coordinates the O2?

A

1 Histidine and Heme Fe

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11
Q

What is hemoglobin?

A

An oxygen transporter in the blood of most animals

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12
Q

True or false: Hemoglobin’s oxygen affinity is independent of pH

A

False. It is pH-dependent

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13
Q

True or false: Hemoglobin’s oxygen affinity can be regulated allosterically by BPG

A

True

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14
Q

True or false: Hemoglobin consists of 4 subunits with C2 symmetry

A

True

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15
Q

True or false: Heme becomes planar when O2 binds

A

True

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16
Q

True or false: The movement of the Fe2+ into the plane of the heme group and the greater planarity of the heme is the trigger of the T state to R state.

A

True

17
Q

What is the model of hemoglobin allostery we discussed in class?

A

Symmetry model

18
Q

True or false: BPG decreases at high altitudes

A

False

19
Q

What is hemocyanin?

A

Hemocyanins are the oxygen binding proteins in blue blood (mollusks and arthropods)

20
Q

What is the symmetry of Hemocyanin?

A

D3 symmetry

21
Q

In the O2 bound state of hemocyanin what coordinates the O2?

A

2 Cu

22
Q

True or false: Hemocyanin contains a heme group.

A

False

23
Q

What is the genetic basis of sickle cell anemia?

A

Point mutation from Glu6 to Val6 in the B chain.

24
Q

Sickle cell anemia causes deoxygenated hemoglobin tetramers to form long fibers. What promotes the sickling effect of HbS?

A

Increasing BPG, increasing blood CO2 (decreasing pH)

25
Q

What stabilizes the deoxygenated state of hemoglobin?

A

Increasing BPG, decreasing pH

Bioc 405 (15 decks)

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