Biochemistry: Myoglobin and Hemoglobin ppt

Question 1

____ is the deficiency in O2 reaching the tissues;

____ is the low concentration of O2 in blood;

____ is the absence of O2

Answer 1

Hypoxia;

Hypoxemia;

Anoxia

Question 2

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

Answer 2

Ventilation; Respiration

Question 3

___ is for O2 storage while ___ is for O2 transport

Answer 3

Myoglbin;

Hemoglobin

Question 4

Proteins with heme as their prosthetic group

Answer 4

Hemoproteins

Question 5

A hemoprotein that catalyzes the breakdown of H2O2

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

Answer 5

Catalase

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

Question 6

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

Answer 6

C is false. Should be alpha-methylene bridges

Question 7

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

Answer 7

False. Should be Oxi from 2+ to 3+

Question 8

The ff are substituents of the beta-position except

A. Methionyl

B. Methyl

C. Vinyl

D. Proprionate

Answer 8

Methionyl

Question 9

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

Answer 9

All

Question 10

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)

Answer 10

B is false. Myoglobin is Monomeric

Question 11

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

Answer 11

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

Question 12

____ 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

Answer 12

Proximal His F8; Distal His E7

Question 14

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

Answer 14

True

Question 15

Creates a special environment for heme for reversible O2 binding

Answer 15

globin

Question 16

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

Answer 16

Unoxygenated

Question 17

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

Answer 17

None of the bonds are false

Question 18

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

Answer 18

True. Ratio for CO poisoning

Question 19

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

Question 20

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

Answer 20

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

Question 21

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

Answer 21

Cooperative binding

Question 22

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

Answer 22

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

Question 23

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

Answer 23

Oxygen Dissociation curve

Question 24

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

Answer 24

Hyperbolic in myo Sigmoidal in hemo

Question 25

pO2 in: 1.) lung capillary is ___mmHg

2. ) in venous blood is ____mmHg
3. ) in active muscles is ___mmHg

Answer 25

100 in lungs

40 in venous blood

20 in active muscles

Question 26

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

Answer 26

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.

Question 27

It is the pO2 that half-saturates a given hemoglobin

Answer 27

P₅₀

Question 28

P50 of HbF is [high/low]?

Answer 28

Low

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

Question 29

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

Answer 29

Bohr Effect

Myoglobin does not experience the Bohr effect because its monomeric

Question 30

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

Answer 30

left

Question 31

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

Answer 31

left due to respiratory alkalosis

Question 32

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

Answer 32

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)

Question 33

CO2 binds with amino groups of hemoglobin to become

Answer 33

carbamate. this form favors shift form R to T state

Question 34

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

Answer 34

2,3-bisphosphoglycerate

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

Hypoxia increases 2,3-BPG

Question 35

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

Answer 35

Fetal Hemoglobin α2ү2

Hemoglobin A2 (HbA2) α2δ2

Question 36

HbA gradually replaces HbF at about what month of pregnancy?

Answer 36

8th month

Question 37

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

Answer 37

False. It is HbF that binds weakly to BPG

Question 38

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

Answer 38

HbA2

Note: HbA1C is high in DM

Question 39

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

Answer 39

Hemoglobinopathy

Question 40

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

Answer 40

Valine

Extra: Lifetime of HbS is 20 days only

Question 41

Sickling of RBC of Hbs patients is usually caused by

Answer 41

low oxygen tension

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

Question 42

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

Answer 42

it is DECREASED pH that causes sickling

Question 43

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

Answer 43

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

Question 44

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

Answer 44

Hemoglobin C Disease

Question 45

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

Answer 45

Methemoglobinemia (MetHgb)

Question 46

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

Answer 46

Chocolate cyanosis

Question 47

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

Answer 47

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

Question 48

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

Answer 48

1 out of 4 - Silent carrir

2/4 - a-thalassemia trait

3/4 - HbH (has hemolytic anemia)

4/4 - Hydrops Fetalis (fetal death)

Question 49

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

Answer 49

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)

Question 50

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

Answer 50

Myoglobinuria