Hemoglobin

Question 1

Oxygen solubitility in H2O

Answer 1

Low

Question 2

2 mechs for supplying oxygen to where it is needed

Answer 2

Circulatory system and system of oxygen transport and storage

Question 3

Mb

Answer 3

Container
Resident in msucles
Stores til needed
Not allosteric

Question 4

Hb

Answer 4

Carrier
Found in RBCs…transports O2, H+, and CO2
Allosteric
Hands O2 off to myoglobin

Question 5

Myoglobin structure

Answer 5

Mostly alpha helical with a heme…binds 1 oxygen

Question 6

Hemoglobin basic structure

Answer 6

2 alpha and 2 beta chains
A2B2 heterotetramer
Each chain binds a heme and is similar to myoglobin

Question 7

Oxygen binding ability due to

Answer 7

Cofactor (prosthetic group) known as a heme

Question 8

Heme location

Answer 8

Sandwiched in a cleft with a histidine on each side

Question 9

Oxygen binding to heme

Answer 9

Iron coordinated by proximal histidine (F8)
Oxygen binding site between iron and distal histidine (E7)
Iron is out of heme plane towards proximal when not bound and move in plane towards distal when oxygen bound

Question 10

Isolated heme binding and what happens in H2O

Answer 10

Isolated heme binds weakly

O2 oxidizes Fe(2) into Fe(3)

Question 11

Oxidized heme

Answer 11

Cannot bind oxygen

Question 12

Heme bound by myoglobin and hemoglobin

Answer 12

Cannot associate with other heme groups

Protein increases heme affinity for O2 and prevents heme from being oxidized

Question 13

Hb binding

Answer 13

Cooperatively (allosteric)

Question 14

Effector or modulator

Answer 14

Allosteric ligand

Question 15

Allostery normally results from

Answer 15

INteractions between subunits in oligomeric proteins

Question 16

Homo vs. heterotropic interactions

Answer 16

Ligands are identical/differ

Question 17

Oxygen type of ligan

Answer 17

Positive homotropic allosteric effector

Question 18

IN metabolically active muscle

Answer 18

Higher Co2 and H+ lead to release of O2

CO2, H+, and BPG Act as negative heterotropic allosteric effectors…BPG also high

Question 19

In alveolar capillaries

Answer 19

Higher pH (low H+) and higher O2 concentration promotes unloading of Co2 and H+ and binding of O2...BPG also low  
O2 is positive, homotropic allosteric effector

Question 20

BPG

Answer 20

Only binds deoxygenated Hb
Needed in order for Hb to release O2
Negative heterotropic allosteric effector

Question 21

Isolated alpha and beta chains

Answer 21

A - like myoglobin…high O2 affinity and not allosteric

B - forms B4 tetramer that is like MB…higher O2 affinity and not allosteric

Question 22

Allosteric properties of Hb from

Answer 22

Interactions between subunits of A2B2 tetramer

Question 23

Quaternary changes upon O2 bidning

Answer 23

alpha(1) and B(2) interface changes as well as vce verse
A(1)B(1) moves about 15 degrees
Oxygenated in relaxed while deoxygenated tense

Question 24

Oxygen binding effect on heme

Answer 24

Pulls on proximal histidine that is part of an alpha helix…causes change to the R state

Stabilizes R state relative to T state

Question 25

Mech of negative allosteric effectors

Answer 25

Stabilize the T state

BPG binds in central cavity between the four subunits

Question 26

Fetal hemoglobin

Answer 26

Higher affinity for oxygen because BPG binds less strongly
Isoform (Hb F vs. Hb A)
Deoxy Hb F can take O2 from Oxy Hb A