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CS2 Exam III > 39: Hemoglobin - Schmidt > Flashcards

39: Hemoglobin - Schmidt Flashcards

1
Q

most abundant form of hemoglobin in adults

A

HbA

a2b2

compromise 97% of total hemoglobin in adults

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2
Q

t or f: the four heme subunits bind O2 with equal affinity

A

false

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3
Q

Hb does not bind O2 efficiently at ____ 02 concentration

A

low

as O2 levels increase, Hb becomes more efficient at binding O2

this gives a sigmoid shape to the binding curve

see slide 3

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4
Q

________ binds O2 with high affinity at low O2 concentration

A

myoglobin

the binding curve is hyperbolic

see slide 3

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5
Q

fetal hemoglobin =

early in embryonic development…
Hb gower 1 =
Hb gower 2 =
Hb Portland L2Y2 =

A

a2g2
z2e2
a2e2
z2g2

gower and portland need to capture O2 from mom and have VERY high oxygen affinity

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6
Q

as development progresses …. reciprocal switch from _ chain synthesis to _ chains synthesis

A

gamma chain to beta chain

a histidine residue in b-chain required for 2,3-BPG binding is replaced with serine in the g-chain (reduces 2,3 affinity and increases oxygen affinity)

leads to replacement of HbF with HbA

HbF comprises less than 2% of total Hb by the end of the first year of life

look at slide 4 / 5

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7
Q

a like globins =

b like globins =

A

a and z (chromosome 16)

b, g, d, e (chromosome 11)

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8
Q

HS-40 is upstream of…

LCR is upstream of…

A

a-like on chrm 16
b-like on chrm 11

these upstream regulatory elements confer high-level, tissue specific expression

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9
Q

what is EKLF? erythroid kruppel-like factor

A

expression increases b-globin gene expression

involved in g–>b globin gene switchin

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10
Q

heinz bodies indicated –>

A

unstable hemoglobins

often form hemichrome and precipitate as heinz bodies

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11
Q

Hb helsinki

A

b-subunit mutation at 2,3BPG binding site –> increased oxygen affinity

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12
Q

Hb kansas

A

b-subunit mutation at a2b2 contact site –> decreased oxygen affinity

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13
Q

Hb Mboston

A

alpha subunit mutation that causes a structural variant that readily form methemoglobin

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14
Q

Hb Mhyde park

A

beta subunit mutation that causes a structural variant that readily form methemoglobin

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15
Q

glutamate replaced with valine at position six of b-globi chain –>

A

Hb S (sickle cell disease)

deoxygenated HbS will polymerize! —> distort RBC shape, circulation block, lysis (chronic hemolytic anemia)

heterozygote = trait
homozygote = disease
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16
Q

treatment of choice in adults with sickle cell

A

hydroxyurea

increases the expression of HbF –> promotes hemoglobin solubility and reduces sickling, painful crises, hospializations

unknown MOA

17
Q

glutamate replaced with lysine at position six of b-globin chain

*only west african origin

A

HbC

Hb C is less soluble than HbA and precipitates

–> less flexible red cells have reduced lifespan (hemolytic anemia)

18
Q

Hb SC =

A

milder than Hb S disease

19
Q

glutamate at position 26 of b-globin chain is replaced with lysine

A

HbE

common in southeast asia (mild anemia and microcytosis only if homozygotes)

–> b-globin chain is not synthesized effectively –> thalassemia

20
Q

reduced synthesis of either type of chian reduces amount of functional tetramer formed =

A

thalassemia

21
Q

a/b thalassemias vs. a/b+ thalassemias

A

no functional globin chain produced

reduced amount of globin chain produced

22
Q

a-thlassemias manifest…

A

during development and in adult life

there are 4 genes for alpha –> lose more = more severe disease

23
Q

bart’s hemoglobin

A

gama4 tetramers form in fetus

poor oxygen carriers

due to only 1 functional a globin gene

24
Q

Hb H

A

b4 tetramers

poor oxygen carriers

precipitates shortening red cell life

due to only 1 functional a globin gene

25
Q

hemoglobin bart’s hydrops fetalis syndrome

A

only embryonic hemoglobins produced to to 4 defective a-globin genes

lethal condition

26
Q

a-thalssemias most often arise by …

A

deletion by homologous recombination

27
Q

Hb constant spring

A

T replaced by C pt mutation

a-globin chain length increased from 141-> 172 aa

looks like a a+ thalssemia because unstable

28
Q

lepore hemoglobin

A

delete part both b and d globin genes

functions poorly as a globin chain

29
Q

how many b genes?

A

one

b-globin gene defects have phenotypes depending on residual abilities left

30
Q

screening techniques for hemoglobinopathies

A

isoelectric focusing(any hemoglobinopathy) or PCR-RFLP(only sickle cell) in neonatal screenings

31
Q

the low O2 environment of the tissue favors…

the high O2 environment of the lungs favors …

A

dissociation

binding

32
Q

binding of 2,3 BPG favors…

A

oxygen dissociation

CS2 Exam III (14 decks)

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