Biochemistry: Myoglobin and Hemoglobin ppt Flashcards

1
Q

____ is the deficiency in O2 reaching the tissues;

____ is the low concentration of O2 in blood;

____ is the absence of O2

A

Hypoxia;

Hypoxemia;

Anoxia

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2
Q

____ is movement of gas into and out of lungs while ___ is exchange of O2 and CO2 across lungs or at cellular level

A

Ventilation; Respiration

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3
Q

___ is for O2 storage while ___ is for O2 transport

A

Myoglbin;

Hemoglobin

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4
Q

Proteins with heme as their prosthetic group

A

Hemoproteins

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5
Q

A hemoprotein that catalyzes the breakdown of H2O2

a. cytochrome
b. catalase
c. hemoglobin
d. myoglobin

A

Catalase

Note: Cytochrome is also an O2 carrier but the it is alternatively reduced and oxidized; Myoglobin and Hemoglobin REVERSIBLY bind O2

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6
Q

Which is FALSE regarding the heme structure?

A. Complex of protoporphyrin IX & ferrous iron (Fe2+)

B. has 4 molecules of pyrrole

C. Linkage: gamma-methylene bridges

D. Iron is held in the center by bonds to the 4 Nitrogens of the porphyrin ring

A

C is false. Should be alpha-methylene bridges

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7
Q

T/F: Oxidation from Fe3+ to Fe2+ destroys the biologic activity of heme

A

False. Should be Oxi from 2+ to 3+

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8
Q

The ff are substituents of the beta-position except

A. Methionyl

B. Methyl

C. Vinyl

D. Proprionate

A

Methionyl

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9
Q

Which of the ff are functions of heme

A. Prosthetic group of myoglobin & hemoglobin

B. O2 binding

C. O2 transport

D. Electron transport

E. Photosynthesis

F. AOTA

G. All but E

A

All

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10
Q

The ff are true of MYOGLOBIN, except?

A. 153-aminoacyl residue polypeptide

B. Tetrameric

C. MW 17,000

D. Compactly folded, roughly spherical

E. Residues are present in 8 right-handed, 7-20 residue α-helices

F. A-H helices (from amino terminal)

A

B is false. Myoglobin is Monomeric

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11
Q

T/F: Myoglobin has a nonpolar surface surrounding a polar interior

A

False. The surface is POLAR with charged amino acids while the interior is NONPOLAR stabilized by hydrophobic interactions

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12
Q

____ binds directly to iron while ____ stabilizes binding of 02 to Fe2+

a. Distal His E7; Proximal His F8
b. Proximal His F8; Distal His E7
c. Proximal His F7; Distal His E8
d. Distal His E8; Proximal His F7

A

Proximal His F8; Distal His E7

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13
Q
A
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14
Q

T/F: Heme lies in between helices E and F

A

True

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15
Q

Creates a special environment for heme for reversible O2 binding

A

globin

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16
Q

Myoglobin is [Oxygenated/Unoxygenated] when iron is outside the palne of the heme ring toward His F8

A

Unoxygenated

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17
Q

Fe2+ in heme has 6 ligand bonds. Which bond DOES NOT occur?

A. 4 bind iron to protoporphyrin plane

B. 5th - His residue in F-alpha-helix (His F8) → proximal side of the protoporphyrin plane

C. 6th - between O2 molecule & His E7 → distal side of the protoporphyrin ring

D. AOTA

E. NOTA

A

None of the bonds are false

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18
Q

T/F: carbon monoxide binds to heme more than oxygen

A

True. Ratio for CO poisoning

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19
Q

Which hemoglobin sub-unit combination does not occur?

A. α2β2 (HbA; normal adult hemoglobin)

B. α2ү2 (HbF; fetal hemoglobin)

C. α2S2 (HbS; sickle cell hemoglobin)

D. α2δ2 (HbA2, minor adult hemoglobin)

E. NOTA

A
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20
Q

The ff are similarities between hemoglobin and myoglobin, EXCEPT?

A. α-polypeptide 8 helical regions

B. Location of the heme

C. β-polypeptide has 8 helical regions

A

A is false because hemoglobin alpha-polypeptide only has 7 helices instead of 8

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21
Q

Phenomenon where O2 binds more rapidly to hemoglobin tetramer if other O2 molecules are already bound

A

Cooperative binding

22
Q

T/F: T state is the high O2-affinity state

A

False. T or tense has low O2 affinity while R or relaxed state has high O2 affinity

23
Q

Shows the relationship between pO2 and quantity of O2 bound (O2 sat)

A

Oxygen Dissociation curve

24
Q

O2 Dissociation curve of myoglobin is ____ while in hemoglobin, it is ____

A

Hyperbolic in myo Sigmoidal in hemo

25
Q

pO2 in: 1.) lung capillary is ___mmHg

  1. ) in venous blood is ____mmHg
  2. ) in active muscles is ___mmHg
A

100 in lungs

40 in venous blood

20 in active muscles

26
Q

T/F: Myoglobin releases its O2 at pO2 >20mmHg?

A

False. Myoglobin still has 90% of its O2 at 20 mmHg. Myoglobin only releases its stored O2 during strenuous exercise where the pO2 can drop as low as 5 mmHg.

27
Q

It is the pO2 that half-saturates a given hemoglobin

A

P50

28
Q

P50 of HbF is [high/low]?

A

Low

Ratio: Low P50 hemoglobin can bind to o2 even at low pO2 (shift to the left)

29
Q

Describes effect of hemoglobin’s O2 affinity to pCO2 and pH which depends on cooperative binding

A

Bohr Effect

Myoglobin does not experience the Bohr effect because its monomeric

30
Q

When blood pH increases, O2 diss. curve shifts to the

A

left

31
Q

The hypoxic ventilatory response (increase in ventilation due to hypoxia) shifts the O2 diss. curve to the

A

left due to respiratory alkalosis

32
Q

The higher the concentration of protons, CO2, and 2,3-BPG, the hemoglobin will shift from?

a. R to T state
b. T to R state

A

R to T state.

Note: low pH, high CO2, and high BPG interfere with O2 binding to heme. This causes the hemoglobin to be in its low-affinity state (T state)

33
Q

CO2 binds with amino groups of hemoglobin to become

A

carbamate. this form favors shift form R to T state

34
Q

Found inside RBC that has a 1:1 concentration as that of Hgb. It stabilizes the T state

A

2,3-bisphosphoglycerate

Extra: BPG bind to Hgb, lowering its O2 affinity (T state)

Hypoxia increases 2,3-BPG

35
Q

alpha 2 gamma 2 is ____ while alpha 2 delta 2 is ____

A

Fetal Hemoglobin α2ү2

Hemoglobin A2 (HbA2) α2δ2

36
Q

HbA gradually replaces HbF at about what month of pregnancy?

A

8th month

37
Q

T/F: HbA binds weakly to 2,3-BPG and thus has higher affinity to O2

A

False. It is HbF that binds weakly to BPG

38
Q

Form of Hgb that appears 12 weeks after birth and is also the most abundant form of glycosylated Hgb

A

HbA2

Note: HbA1C is high in DM

39
Q

Group of disorders of structurally abnormal Hgb or low production of normal Hgb

A

Hemoglobinopathy

40
Q

HbS or the sickle cell disease is due to a point mutation of the beta globin chains where glutamate is replaced by?

A

Valine

Extra: Lifetime of HbS is 20 days only

41
Q

Sickling of RBC of Hbs patients is usually caused by

A

low oxygen tension

(such as in peripheral capillaries. Sickle RBCs block the vessels causing ischemia leading to pain and/or death of cells

42
Q

The ff variables increase sickling of RBC in HbS patients, EXCEPT:

A. Decreased O2 tension

B. High altitudes or flying in a nonpressurized plane

C. Increased pCO2

D. Increased pH

E. Increased concentration of 2,3 BPG in RBCs

A

it is DECREASED pH that causes sickling

43
Q

Give an advantage of the heterozygous carrier of the HbS gene?

A

less susceptible to malaria because the parasite P. falciparum cannot complete its life cycle in the sickled RBC

44
Q

Substitution from glutamate to lysine at the 6th position of the beta globin chain causes what disease?

A

Hemoglobin C Disease

45
Q

When iron in heme is in its ferric form, it causes what condition?

A

Methemoglobinemia (MetHgb)

46
Q

Brownish-blue coloration of the skin due to brown-colored blood is a condition termed?

A

Chocolate cyanosis

47
Q

Disease where the synthesis of beta-globin chain is decreased or absent

A

Beta-thalassemia

Notes:

B-thalassemia minor affects only 1 beta globin, hence no treatment

B-thalassemia major renders the two beta-globins defective. Patients become anemic. Treatment is transfusion but may cause hemosiderosis

48
Q

alpha-thalassemia has 4 subtypes depending on the number of genes deactivated. Enumerate.

A

1 out of 4 - Silent carrir

2/4 - a-thalassemia trait

3/4 - HbH (has hemolytic anemia)

4/4 - Hydrops Fetalis (fetal death)

49
Q

Condition where His F8 is replaced by tyrosine causing iron to be in its ferric form which favors the R state.

A

Hemoglobin M

Note: Hgb in the R state fails to release O2 causing hypoxia which stimulates EPO leading to polycythemia

(M for Many RBCs, chos)

50
Q

Massive crush injury may cause muscle fibers to release their myoglobin, causing dark red urine. This condition is called

A

Myoglobinuria