Chapter 15- Hemoglobin Flashcards by Ty Nicholas

_____ stores O2 in the muscles

Myoglobin (Mb)

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_____ transports O2 in the blood

Hemoglobin (Hb)

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How many units of O2 can Mb store? Hb?

Mb- 1
Hb- 4

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Which group does the O2 bind to?

Heme group

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How many heme groups does Mb contain? Hb?

Mb- 1
Hb- 4

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Heme groups consist of:

A porphyrin derivative (pyrrole rings linked by methane bridges)
Centrally bound iron atom (Fe (II))

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A heme group is called a ____ _____

prosthetic group

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The iron atom in the heme group normally remains in the ____ oxidation state

Fe (II)

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Color of deoxyHb? oxyHb?

Dark purplish
Brilliant red

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Mb and Hb possess reversible action which means they can

bind O2 and release it.

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Lower value of Kd means _____ affinity

higher

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Lower value of Ka means _____ affinity

lower

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Higher affinity means _____ binding

stronger

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Mb-O2 dissociation follows a _____ curve

hyperbolic

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Why do muscles need O2?

O2 is used by muscles to form ATP

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When is Mb most saturated?

The oxygen concentrations are high (aka the muscle is resting)

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O2 binding to Hb follows a _____ curve

sigmoidal

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The sigmoidal curve of O2 binding in Hb is indicative of a ____ _____

cooperative process

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Mb is ill-suited for the ______ of O2, which means its more suited as an ___ ______ ______

transport
O2 storage protein

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How does Hb solve the problem of being able to bind and release O2?

A cooperative transition from low affinity to high-affinity state

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Two conformations for Hb

T state- tensed
R state- relaxed

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binding of O2 in Hb leads to ______ _____

conformational changes

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Binding of O2 is a form of _______ ______

Allosteric Binding

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What does allosteric binding mean in terms of O2 binding

The binding of a ligand to one site affects the binding properties of another site on the same protein

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The conformational changes of binding sites of Hb make it easier for

O2 to bind

After first O2 binds, affinity _____ _______

Increases 100-fold

In deoxyhemoglobin, Fe 2+ is ____ spin

high

When O2 binds, Fe2+ is ____ spin

low

IF nH= 1

Binding is not cooperative

Mb has an n= ?

nH> 1 means

Positive cooperativity (Hb)

nH < 1

Negative cooperativity

What does negative cooperativity mean?

binding of one ligand impedes the binding of others.

What does nH correspond to?

the degree of cooperativity between binding sites

n of Hb=?

2.8

What is n?

the slope of the Hill plot

What is the upper limit of nH? what does it mean in terms of binding?

nH=n, all binding sites bind ligand simultaneously

The affinity of Hb changes as ____ changes

pO2

The hill plot of Hb is

curvilinear

At low pO2, Y~

At low pO2, Hb subunits compete ___ for O2 and the Hill plot has a slope of ___

independently, 1

At high pO2, Y~

At low pO2, how many O2 have bound to the Hb?

Most likely 0, few have bound 1

At high pO2, how many O2 have bound to the Hb?

at least 3/4 of binding sites are occupied

Which pO2 level has the maximum cooperativity?

intermediate pO2

The slope of the Hill plot at high pO2?

slope =1

The slope of the Hill plot at intermediate pO2?

slope ~3

the differential affinity of Hb for O2 in the lungs and peripheral tissues stems from ______ ____ which are ______ ______

effector molecules, allosteric effectors

Oxygen is a ____ and _____ allosteric effector

positive, homotropic

the other three allosteric effectors of O2

- CO2 - H+ - 2,3 BPG

CO2, H+, and 2,3 BPG are _____ and _____ allosteric effectors which means they promote the _____

Negative, Heterotropic, dissociation of O2

pH in the lungs=_____ pH in tissues = ______

7.6 in the lungs 7.2 in the tissues

The tissues possess a ___ pH and a ____ [CO2]

low, high

The affinity of Hb for O2 is ____ in the tissues which means O2 is ______

decreased, released

The lungs possess a ____ pH and a ____ [CO2]

high, low

The affinity for Hb for O2 is ____ in the lungs which means O2 _____

increased, Binds

Bohr Effect

The effect of pH and [CO2] on Hb binding

The H+ effect states

protonation of HIS146 is responsible for stabilizing the T state

The CO2 effect states

CO2 binds as a carbamate group to the N-term of each subunit which forms additional salt bridges stabilizing the T state

The CO2 effect leads to the production of ____

H+

BPG binds tightly to deoxyHb in a ____ ratio

1:1

BPG stabilizes the ______

T state

BPG inhibits O2 binding on ______ subunits of Hb

all 4

Without BPG little O2 would be _____

released by Hb

Synthesis of BPG increases when exceeding altitudes above _____

4,000m

Increased BPG causes a small difference in _____ and a large difference in _____

O2 binding in the lungs, O2 release in tissues

Newborn babies after birth will synthesize more ____ than ____ subunits

gamma, beta

Fetal Hb has _______ than maternal Hb

greater affinity

How can a fetus extract enough O2 from the mother's blood?

Fetus synthesizes gamma subunits instead of beta which results in a tetramer with a lower affinity for BPG

Sickle cell anemia (HbS) is caused by a ______ which changed _____ to ____ in the beta chain

single mutation, Glu to Val

The mutation for HbS occurs on the _____ of Hb which creates a ________

surface, Hydrophobic spot

The hydrophobic spot on the HbS will form _____ which distorts RBC shape

Fibrils

How is sickle cell treated?

Hydroxyurea and CRISPR gene editing

How does hydroxyurea partially treat sickle cell anemia?

elevates the expression of fetal gamma subunit

Why is sickle cell anemia not observed until several months after birth?

That is when the fetal gamma subunit mutates into beta S subunit

Chapter 15- Hemoglobin Flashcards

(75 cards)