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Biochemistry > Chapter 7 > Flashcards

Chapter 7 Flashcards

1
Q

What is hemoglobin?

A

Oxygen transport protein circulating in the blood

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2
Q

How many subunits are in hemoglobin?

A

4: Two alpha and two beta chains

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3
Q

What is myoglobin?

A

Oxygen storage protein in muscle cells

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4
Q

How many subunits are in myoglobin?

A

One

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5
Q

What holds heme structure in place?

A

F and H helix

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6
Q

What prevents Fe2+ from binding to unwanted molecules?

A

Valine and Phenylalanine

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7
Q

What is oxymyoglobin?

A

Bound to O2, bright red

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8
Q

What is deoxymyoglobin?

A

No O2 bound, purplish

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9
Q

What is metmyoglobin?

A

Fe2+ oxidized to Fe 3+, brownish
No longer binds to O2

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10
Q

What is the equation of fractional saturation for myoglobin?

A

Y(O2) = [MbO2]/ [Mb]+[MbO2]

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11
Q

What is the equation for the dissociation constant of myoglobin?

A

Kd = [Mb][O2]/[MbO2]

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11
Q

What does a low Kd value mean?

A

The structure is more likely to stay together

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11
Q

What does a high Y(O2) value for myoglobin mean?

A

There is a high [MbO2] compared to [Mb]

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12
Q

What does a high Kd value mean?

A

The structure is more likely to break apart

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13
Q

What is the equilibrium value (k)?

A

The point where there is 50% saturation

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14
Q

What is arterial O2 pressure?

A

100 torr

15
Q

What is venous O2 pressure?

A

30 torr

16
Q

What does a Y(O2) value of 1 mean?

A

All myoglobin/hemoglobin is saturated with oxygen

17
Q

What is the hill equation?

A

Y(O2) = (pO2)^n / [(p50)^n + (pO2)^n]

18
Q

What does the hill constant (n) describe?

A

Increases with cooperativity

19
Q

How does O2 binding to hemoglobin affect cooperativity?

A

Positively (increases n)

20
Q

How does oxygen not being bound affect the heme structure?

A

0.06 nm out of place

21
Q

How does oxygen being bound affect the heme structure?

A

Fe2+ moves into the plane
This causes a series of conformational changes in hemoglobin

22
Q

What is allosteric regulation?

A

Positive or negative regulators that bind to another site than the O2 binding site

23
Q

What is the R state of allosteric regulation?

A

Relaxed (bound to O2)

24
Q

What is the T state of allosteric regulation?

A

Taut (not bound to O2)

25
Q

How does the state of hemoglobin affect O2 binding?

A

Hemoglobin T state requires higher O2 concentration to bind – the more heme structures bound to O2 the easier oxygen binds to the remaining heme structures

26
Q

What is the Bohr Effect?

A

Decrease in O2 binding by H+

27
Q

What is the effect on oxygen binding when pH is increased?

A

An increase in pH leads to more O2 binding described by the Bohr effect

High pH -> low [H+] -> higher O2 binding

28
Q

What is the effect of CO2 formation on oxygen binding to Mb/Hg?

A

CO2 formation decreases O2 binding

29
Q

What enzyme forms carbonic acid?

A

Carbonic anhydrase

30
Q

Why is the formation of H2CO3 desired from CO2?

A

CO2 is not soluble but carbonic acid is

31
Q

What is BPG?

A

Allosteric effect of hemoglobin

32
Q

What is the function of BPG?

A

Stabilizes the hemoglobin T state, therefore requiring a higher pO2 for O2 binding

33
Q

How does BPG work?

A

The negative charge interacts with 2-Lys, 4-His, and 2 N-termini

34
Q

What is the difference between adult and fetal hemoglobin?

A

In fetal hemoglobin, there are gamma strands instead of beta strands

35
Q

What causes sickle-cell anemia?

A

Substitution of valine from glutamic acid in the 6th position of beta-chain (E6V)

36
Q

What does the E6V mutation of sickle-cell result in?

A

Hydrophobic pocket created in deoxy- state; allows for valine to bind to the pocket

Biochemistry (17 decks)

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