Myoglobin and Hemoglobin ppt Flashcards
____ is the deficiency in O2 reaching the tissues;
____ is the low concentration of O2 in blood;
____ is the absence of O2
Hypoxia;
Hypoxemia;
Anoxia
____ is movement of gas into and out of lungs while ___ is exchange of O2 and CO2 across lungs or at cellular level
Ventilation; Respiration
___ is for O2 storage while ___ is for O2 transport
Myoglbin;
Hemoglobin
Proteins with heme as their prosthetic group
Hemoproteins
A hemoprotein that catalyzes the breakdown of H2O2
a. cytochrome
b. catalase
c. hemoglobin
d. myoglobin
Catalase
Note: Cytochrome is also an O2 carrier but the it is alternatively reduced and oxidized; Myoglobin and Hemoglobin REVERSIBLY bind O2
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
C is false. Should be alpha-methylene bridges
T/F: Oxidation from Fe3+ to Fe2+ destroys the biologic activity of heme
False. Should be Oxi from 2+ to 3+
The ff are substituents of the beta-position except
A. Methionyl
B. Methyl
C. Vinyl
D. Proprionate
Methionyl
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
All
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)
B is false. Myoglobin is Monomeric
T/F: Myoglobin has a nonpolar surface surrounding a polar interior
False. The surface is POLAR with charged amino acids while the interior is NONPOLAR stabilized by hydrophobic interactions
____ 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
Proximal His F8; Distal His E7
T/F: Heme lies in between helices E and F
True
Creates a special environment for heme for reversible O2 binding
globin
Myoglobin is [Oxygenated/Unoxygenated] when iron is outside the palne of the heme ring toward His F8
Unoxygenated
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
None of the bonds are false
T/F: carbon monoxide binds to heme more than oxygen
True. Ratio for CO poisoning
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
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 is false because hemoglobin alpha-polypeptide only has 7 helices instead of 8
Phenomenon where O2 binds more rapidly to hemoglobin tetramer if other O2 molecules are already bound
Cooperative binding
T/F: T state is the high O2-affinity state
False. T or tense has low O2 affinity while R or relaxed state has high O2 affinity
Shows the relationship between pO2 and quantity of O2 bound (O2 sat)
Oxygen Dissociation curve
O2 Dissociation curve of myoglobin is ____ while in hemoglobin, it is ____
Hyperbolic in myo Sigmoidal in hemo
pO2 in: 1.) lung capillary is ___mmHg
- ) in venous blood is ____mmHg
- ) in active muscles is ___mmHg
100 in lungs
40 in venous blood
20 in active muscles
T/F: Myoglobin releases its O2 at pO2 >20mmHg?
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.
It is the pO2 that half-saturates a given hemoglobin
P50
P50 of HbF is [high/low]?
Low
Ratio: Low P50 hemoglobin can bind to o2 even at low pO2 (shift to the left)
Describes effect of hemoglobin’s O2 affinity to pCO2 and pH which depends on cooperative binding
Bohr Effect
Myoglobin does not experience the Bohr effect because its monomeric
When blood pH increases, O2 diss. curve shifts to the
left
The hypoxic ventilatory response (increase in ventilation due to hypoxia) shifts the O2 diss. curve to the
left due to respiratory alkalosis
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
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)
CO2 binds with amino groups of hemoglobin to become
carbamate. this form favors shift form R to T state
Found inside RBC that has a 1:1 concentration as that of Hgb. It stabilizes the T state
2,3-bisphosphoglycerate
Extra: BPG bind to Hgb, lowering its O2 affinity (T state)
Hypoxia increases 2,3-BPG
alpha 2 gamma 2 is ____ while alpha 2 delta 2 is ____
Fetal Hemoglobin α2ү2
Hemoglobin A2 (HbA2) α2δ2
HbA gradually replaces HbF at about what month of pregnancy?
8th month
T/F: HbA binds weakly to 2,3-BPG and thus has higher affinity to O2
False. It is HbF that binds weakly to BPG
Form of Hgb that appears 12 weeks after birth and is also the most abundant form of glycosylated Hgb
HbA2
Note: HbA1C is high in DM
Group of disorders of structurally abnormal Hgb or low production of normal Hgb
Hemoglobinopathy
HbS or the sickle cell disease is due to a point mutation of the beta globin chains where glutamate is replaced by?
Valine
Extra: Lifetime of HbS is 20 days only
Sickling of RBC of Hbs patients is usually caused by
low oxygen tension
(such as in peripheral capillaries. Sickle RBCs block the vessels causing ischemia leading to pain and/or death of cells
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
it is DECREASED pH that causes sickling
Give an advantage of the heterozygous carrier of the HbS gene?
less susceptible to malaria because the parasite P. falciparum cannot complete its life cycle in the sickled RBC
Substitution from glutamate to lysine at the 6th position of the beta globin chain causes what disease?
Hemoglobin C Disease
When iron in heme is in its ferric form, it causes what condition?
Methemoglobinemia (MetHgb)
Brownish-blue coloration of the skin due to brown-colored blood is a condition termed?
Chocolate cyanosis
Disease where the synthesis of beta-globin chain is decreased or absent
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
alpha-thalassemia has 4 subtypes depending on the number of genes deactivated. Enumerate.
1 out of 4 - Silent carrir
2/4 - a-thalassemia trait
3/4 - HbH (has hemolytic anemia)
4/4 - Hydrops Fetalis (fetal death)
Condition where His F8 is replaced by tyrosine causing iron to be in its ferric form which favors the R state.
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)
Massive crush injury may cause muscle fibers to release their myoglobin, causing dark red urine. This condition is called
Myoglobinuria
