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Hematology > Lecture 13 Hemoglobin Structure > Flashcards

Lecture 13 Hemoglobin Structure Flashcards

1
Q

Hemoglobin Structure

A

Four heme and 2 alpha and beta globin chains

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2
Q

Primary structure of globin

A

amino acid sequence

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3
Q

Secondary structure of globin

A

helical and non-helical segments

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4
Q

Tertiary structure of globin

A

pretzel-like helical configuration with incorporation of heme group

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5
Q

Quaternary structure of globin

A

complete Hgb molecule

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6
Q

Adult Hgb concentrations

A

HgbA1: 97%, HgbA2: 2.5%, HgbF: <1%

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7
Q

Portland hemoglobin

A

2 zeta, 2 gamma, embryonic

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8
Q

Gower 1

A

2 zeta, 2 epsilon, embryonic

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9
Q

Gower 2

A

2 alpha, 2 epsilon, embryonic

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10
Q

HgbF

A

2 alpha, 2 gamma, newborn and adult

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11
Q

HgbA1

A

2 alpha, 2 beta, newborn and adult

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12
Q

HgbA2

A

2 alpha, 2 delta, newborn and adult

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13
Q

Newborn Hgb Concentrations

A

HgbF: 80%, HgbA1: 20%, HgbA2: <0.5%

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14
Q

Tense hemoglobin

A

Hgb without oxygen bound to it

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15
Q

Relaxed homglobin

A

Hgb with oxygen bound to it

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16
Q

of oxygens Hgb can bind

A

4

17
Q

O2 Dissociation Curve (Normal)

A

PO2 = 27mmHg, 50% O2 saturation, P50: amount of O2 needed to saturate 50% of Hgb

18
Q

O2 dissociation curve (shift to left)

A

P50 < 27mmHg, higher O2 affinity

19
Q

O2 dissociation curve (shift to right)

A

P50 > 27 mmHg, lower O2 affinity

20
Q

2,3-BPG

A

bound to tense hemoglobin (unable to transport O2), unbinds when hemoglobin relaxed

21
Q

Causes of shift to left

A
  • low body temp
  • decreased pC02
  • depleted 2,3-BPG
  • increased pH
  • abnormal HgB with high affinity such as HgbF
22
Q

Causes of shift to the right

A
  • increased body temp
  • elevated pCO2
  • increased 2,3-BPG levels
  • decreased pH
  • altitude
  • hypoxia from heart failure, lung disease, anemia
  • abnormal Hgb with decreased O2 affinity
23
Q

Myoglobin

A
  • heme found in cardiac and skeletal muscle
  • greater affinity for O2
  • elevated in renal disease, heart attack, and muscle damage
24
Q

Bohr effect

A
  • change in pH in blood
25
Q

Bohr effect (shift to left)

A
  • decreased H+ ions
  • increased pH
  • increased O2 affinity
26
Q

Bohr effect (shift to right)

A

increased H+ ions
decreased pH
decreased O2 affinity

27
Q

Chloride shift

A

bicarbonate diffuses out of RBC and exchanges with Cl-
maintains proper charge within RBC
bicarbonate travels to lungs and expired

28
Q

Measurement of Hemoglobin: Cyanmethemoglobin method

A

potassium ferricyanide combines with free Hgb to from methemoglobin
potassium cyanide combines with methemoglobin to form cyanmethemoglobin
absorbance at 540 nm measured

29
Q

Measurement of Hemoglobin: Sodium lauryl sulfate method (Sysmex)

A

does not generate toxic wastes

SLS converts Hgb to SLS-methemoglobin

30
Q

Chemically Modified Hemoglobins: Methemoglobin

A

Fe3+ -> cannot bind oxygen
formed by spontaneous oxidation
*brownish to bluish in color: does not revert to red upon osygen exposure
methemoglobin reductase pathway converts mthemoglobin back to hemoglobin
shift to left in dissociation curve
hypoxia and cyanosis
causes: strong oxidants (nitrites), decreased methemoglobin reductase, HgbM (inherited)
treatment: removal of causative agent, administration of ascorbic acid or methylene blue (reducing agents)
measured at peak range 620-640 nm

31
Q

Chemically Modified Hemoglobins: Sulfhemoglobins

A 
addition of hydrogen sulfide (S) atom to Hgb
greenish pigment
shift to right in dissociation curve
retains iron in ferrous state but can't carry O2
irreversible change
cyanosis
treatment: prevention of offending agent
measured at 620 nm
32
Q

Chemically Modified Hemoglobins: Carboxyhemoglobins

A

CO combines with heme iron
Hgb affinity for CO 240 times greater and O2 release 10000x lower
blood is cherry red
causes: automobile exhaust, coal gas, house fires, unmaintained home heating systems
shift to left of dissociation curve
10-15%: headaches and dizziness
50-70%: coma and convulsions
80% and above: immediately fatal
treatment: remove source, administer high O2, hyperbaric O2 therapy
measured at 541 nm

Hematology (10 decks)

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