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Fundamentals Block 3 > Hemoglobin Structure and Function > Flashcards

Hemoglobin Structure and Function Flashcards

1
Q

what is the size and shape of red blood cells

A

-biconcave discs
-7.8 diameter, thick rim is 2.5 microns, thin center is 1 micron; average volume is 90-95

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2
Q

RBC’s cytoskeleton proteins confer large deformation capacity to RBC’s allowing them to…..

A

squeeze through capillaries

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3
Q

can RBC counts be increased?

A

yes when stimulated (higher altitudes)

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4
Q

sites of erythropoiesis and production of RBCs by age

A

-yolk sac: first few weeks of gestation
-Liver (spleen & lymph nodes): mid-trimester
-bone marrow: last month of gestation through adulthood

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5
Q

what is the lineage of red blood cells

A

proerythroblast
basophil erythroblast
polychromatophil erthroblast
orthochromatic erythroblast
reticulocyte
erythrocyte

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6
Q

usually devoid of nucleus, mitochondria, golgi apparatus, ribosomes, and other organelles

A

erythrocytes

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7
Q

retain a small amount of ER and mRNA, supporting continued hemoglobin synthesis

A

reticulocytes

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8
Q

what is the life span of RBCs

A

120 days

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9
Q

RBCs ATP is generated by ___________

A

glycolysis

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10
Q

Normal hemoglobin concentration is _______ per 100mL of packed red blood cells

A

34 g

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11
Q

hematocrit

A

packed cell volume

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12
Q

what is normal hematocrit

A

40-45% (slightly lower in women)

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13
Q

normal hemoglobin is _____per mL of blood

A

14-15 g

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14
Q

O2 carrying capacity is 1.34 mL/g Hgb or _________________/100mL of blood

A

19-20 mL O2

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15
Q

what are the steps for formation of hemoglobin

A

1) 2 succinyl-CoA + 2 glycine —> pyrrole
2) 4 pyrrole—> protoporphyrin IX
3) protoporphyrin IX + Fe++ —-> heme
4)heme + polypeptide—> hemoglobin chain (alpha or beta)
5) 2 alpha chains + 2 beta chains—> hemoglobin A

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16
Q

there are several types of globin chains resulting from…..

A

differential gene expression

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17
Q

what is the predominant form of hemoglobin in adults

A

hemoglobin A

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18
Q

each globin chain is associated with one heme group containing one atom of ____

A

iron Fe2+

19
Q

each of the four iron atoms can bind loosely and reversibly with ____________

A

one molecule/2 atoms of oxygen

20
Q

how many oxygen atoms/molecules can each hemoglobin molecules transport

A

8 atoms/4 molecules

21
Q

Hemoglobin affinity for O2 changes accordign to the number of ?

A

heme groups already bound to O2

22
Q

each O2 molecule that binds to hemoglobin facilitates …..

A

the binding of the next O2 molecule

23
Q

tense state (T)

A

deoxygenated

24
Q

relaxed state (R)

A

oxygenated

25
Q

what are the important factors that contribute to the modulation of hemoglobin affinity for O2 by favoring one state over the other?

A

carbon dioxide
hydrogen ions
2,3-diphosphoglycerate

26
Q

the affinity of hemoglobin to bind to O2 is inversely related to both ……

A

acidity (pH) and concentration of Co2 in the surrounding environment

27
Q

binding of Hydrogen ions to the polypeptide portions of hemoglobin favors hemoglobin conformation in what state?

A

tense (T)

28
Q

what are the basic premises of the Bohr Effect?

A

when CO and H+ levels increase, hemoglobin is altered in 3 ways:
-hemoglobin binds with CO2 to form carbaminohemoglobin (HbCO2)
-Hb becomes protonated (HHb+)
-Hb’s affinity for oxygen decreases and Hb-O2 dissociation curve shifts to the right

29
Q

2,3-DPG is formed during the conversion of _________________to __________via an alternative pathway to the main glycolytic pathway by which ATP is generated during glycolysis.

A

glucose to lactate

30
Q

What happens when 2,3-DPG binds to the central charged cavity of deoxyhemoglobin?

A

stabilizing hemoglobin in the T state, this reducing affinity for O2

31
Q

what happens when there is high O2 in the lungs?

A

it displaces CO2 and H+ and reduces available binding sites for 2,3-DPG since Hb shifts to relaxed state

32
Q

what happens when there is high CO2 and H+ in the tissues?

A

O2 is displaced and it increases available binding sites for 2,3-DPG since Hb shifts to T state

33
Q

What factors can alter Hb affinity for O2, CO2, and 2,3-DPG and affect Hb main function to transport O2 and assist in acid-base regulation?

A

-living in high altitudes (increased 2,3-DPG levels)
-heart failure (reduce O2 delivery to tissue & lead to lung congestion
-asthma
-heavy smoking
-genetic variants that alter Hb affinity for O2 or its modulators

34
Q

what are naturally occurring variants that alter Hb-O2 dissociation curve?

A

-HbF has low affinity for 2,3-DPG bc they dont have the binding site, thus has a higher affinity for O2/double Bohr affect
-alpha or beta Thalassemias: reduced production of globins due to genetic deletion of the gene alleles that form these globins, with varying degrees of disease severity
-AA substitution in critical portions of Hb
-methemoglobin (MetHb) can be acquired or inherited and results in increase levels of heme with Fe3+ (cant bind O2) instead of the normal Fe2+
-sickle cell anemia

35
Q

describe the mutation that causes sickle hemoglobin (HbS)

A

-a single nucleotide substitution (A to T) in the codon for amino acid 6, which converts glutamic acid codon to valine codon

36
Q

Hemoglobin of homozygous individuals forms elongated crystals when exposed to ___________________; this leads to vascular occlusion and hemolysis

A

low oxygen

37
Q

what does the double Bohr effect in fetal hemoglobin allow for?

A

O2 can pass more easily from maternal HbA to fetus HbF in placenta bc of the higher affinity for O2

38
Q

what is the root of carbon monoxide poisoning?

A

carbon monoxide has 250 times higher affinity for the heme group than O2

39
Q

how does CO shift the Hb-O2 dissociation curve?

A

shifts the curve down and leftward and reduces the plateau

40
Q

what is the role of Hb in CO2 transport and acid-base regulation?

A

the majority of CO2 travels as bicarbonate (HCO3) and H+ which are converted to H2O and CO2 by carbonic anhydrase

41
Q

describe myoglobin

A

-has higher affinity for O2 and serves mainly as a reservoir of O2 for exercising muscle
-hyperbolic dissociation curve (releasing O2 when O2 levels are low in tissues)
-helps with intracellular O2 transport (from plasma membrane to mitochondria)

42
Q

how does the structure of myoglobin differ from that of hemoglobin

A

myoglobin is only a single subunit protein compared to the 4 subunits in hemoglobin

43
Q

haldane effect

A

O2 displaces Co2 from hemoglobin
in the tissues

44
Q

bohr effect

A

CO2 and H+ displace O2 from hemoglobin
in the lungs

Fundamentals Block 3 (15 decks)

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