Hemoglobin

Question 1

final enzyme of electron transport

Answer 1

cytochrome oxidase - O2 is reduced to H2O

Question 2

facilitates O2 diffusion to the mitochondrion

Answer 2

Mb

Question 3

function of Mb

Answer 3

intracellular transport and temporary storage of O2 needed for aerobic metabolism of muscle

Question 4

secondary structure of Mb

Answer 4

8 a-helices

Question 5

quaternary structure of Hb

Answer 5

a2B2

• 2 x a:B dimers
• quilibrium favors tetramer

Question 6

ApoHb vs HoloHb

Answer 6

protein without vs with prosthetic group

-HoloHb = 1 heme/subunit = 4 hemes

Question 7

how many hemes/O2 binding sites in Hb

Answer 7

4 (1/subunit)

Question 8

basis for Hb’s cooperative binding, resulting in a sigmoid binding curve

Answer 8

T vs R

-R = more O2 bound = higher O2 affinity until Hb molecule is sat’d

Question 9

porphyrin

Answer 9

• tetrapyrrole

- forms protoporphyrin IX, which chelates Fe

Question 10

metal chelating site on Hb

Answer 10

• binds Fe

- 4 nitrogens of 4 pyrrole groups point inward

Question 11

substituent groups on heme prosthetic group (a pyrrole)

Answer 11

4 methyl, 2 vinyl, 2 propionate

Question 12

state of Fe in deoxyHb

Answer 12

ferrous = Fe(II)

-reduced

Question 13

(high/low) O2 affinity at P50

Answer 13

high

Question 14

Mb vs Hb curve

Answer 14

hyperbolic vs sigmoidal

Question 15

Mb ___ O2 in conditions under which Hb ____ it

Answer 15

binds

releases

Question 16

Which has higher P50 (Mb/Hb)

Answer 16

Hb

Question 17

O2 binding negative effectors

Answer 17

decrease affinity of O2 for Hb allows unloading in tissues, while loading can occur in lungs
-BPG, CO2, H+

Question 18

O2 binding positive effectors

Answer 18

increase affinity of O2 for Hb - bad, can’t unload

Question 19

BPG

Answer 19

stabilizes T state, lowers affinity of Hb for O2

Question 20

BPG binds to and stabilizes ______, and ______ Hb’s affinity for O2

Answer 20

T quarternary state of Hb

decreases

Question 21

Hb’s affinity for O2 is fine-tuned by altering this concentration in the blood

Answer 21

BPG

Question 22

shift Hb curve right

Answer 22

unload

ex. BPG

Question 23

short term acclimation to low O2 pressure

Answer 23

shift Hb curve right with BPG; deliver same amt of O2 as at sea level without reducing tissue O2 pressure

Question 24

does pH modulate Mb’s affinity for O2?

Answer 24

no

Question 25

pH in lungs which allows for higher Hb-O2 affinity

Answer 25

high pH, low [H+]

Question 26

pH in tissues which allows for lower Hb-O2 affinity

Answer 26

low pH, high [H+]

Question 27

carbamylation of Hb

Answer 27

• CO2 combines reversibly with N on protein

- favors T state - reduced Hb-O2 affinity

Question 28

effect of CO2 and H+ on HB-O2 affinity

Answer 28

capillaries: CO2 stabilizes T state, O2 is released

- H+ further reduces affinity

Question 29

why does fetal Hb bind O2 with higher affinity

Answer 29

fetal Hb has lower affinity for BPG

Question 30

HbS

Answer 30

• a2B2

- sickle cell anemia

Question 31

HbH

Answer 31

• B4

- a-thalassemia

Question 32

HbBarts

Answer 32

gamma4

-a-thalassemia

Question 33

methemoglobin

Answer 33

ferric - doesn’t bind O2

Question 34

sign of methemoglobinemia

Answer 34

cyanosis