Lecture 13 Hemoglobin Structure

Question 1

Hemoglobin Structure

Answer 1

Four heme and 2 alpha and beta globin chains

Question 2

Primary structure of globin

Answer 2

amino acid sequence

Question 3

Secondary structure of globin

Answer 3

helical and non-helical segments

Question 4

Tertiary structure of globin

Answer 4

pretzel-like helical configuration with incorporation of heme group

Question 5

Quaternary structure of globin

Answer 5

complete Hgb molecule

Question 6

Adult Hgb concentrations

Answer 6

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

Question 7

Portland hemoglobin

Answer 7

2 zeta, 2 gamma, embryonic

Question 8

Gower 1

Answer 8

2 zeta, 2 epsilon, embryonic

Question 9

Gower 2

Answer 9

2 alpha, 2 epsilon, embryonic

Question 10

HgbF

Answer 10

2 alpha, 2 gamma, newborn and adult

Question 11

HgbA1

Answer 11

2 alpha, 2 beta, newborn and adult

Question 12

HgbA2

Answer 12

2 alpha, 2 delta, newborn and adult

Question 13

Newborn Hgb Concentrations

Answer 13

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

Question 14

Tense hemoglobin

Answer 14

Hgb without oxygen bound to it

Question 15

Relaxed homglobin

Answer 15

Hgb with oxygen bound to it

Question 16

of oxygens Hgb can bind

Answer 16

4

Question 17

O2 Dissociation Curve (Normal)

Answer 17

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

Question 18

O2 dissociation curve (shift to left)

Answer 18

P50 < 27mmHg, higher O2 affinity

Question 19

O2 dissociation curve (shift to right)

Answer 19

P50 > 27 mmHg, lower O2 affinity

Question 20

2,3-BPG

Answer 20

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

Question 21

Causes of shift to left

Answer 21

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

Question 22

Causes of shift to the right

Answer 22

• 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

Question 23

Myoglobin

Answer 23

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

Question 24

Bohr effect

Answer 24

• change in pH in blood

Question 25

Bohr effect (shift to left)

Answer 25

- decreased H+ ions - increased pH - increased O2 affinity

Question 26

Bohr effect (shift to right)

Answer 26

increased H+ ions decreased pH decreased O2 affinity

Question 27

Chloride shift

Answer 27

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

Question 28

Measurement of Hemoglobin: Cyanmethemoglobin method

Answer 28

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

Question 29

Measurement of Hemoglobin: Sodium lauryl sulfate method (Sysmex)

Answer 29

does not generate toxic wastes | SLS converts Hgb to SLS-methemoglobin

Question 30

Chemically Modified Hemoglobins: Methemoglobin

Answer 30

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

Question 31

Chemically Modified Hemoglobins: Sulfhemoglobins

Answer 31

``` 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 ```

Question 32

Chemically Modified Hemoglobins: Carboxyhemoglobins

Answer 32

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