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Flashcards in Hemoglobin Deck (26)
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1

Oxygen solubitility in H2O

Low

2

2 mechs for supplying oxygen to where it is needed

Circulatory system and system of oxygen transport and storage

3

Mb

Container
Resident in msucles
Stores til needed
Not allosteric

4

Hb

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

5

Myoglobin structure

Mostly alpha helical with a heme...binds 1 oxygen

6

Hemoglobin basic structure

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

7

Oxygen binding ability due to

Cofactor (prosthetic group) known as a heme

8

Heme location

Sandwiched in a cleft with a histidine on each side

9

Oxygen binding to heme

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

10

Isolated heme binding and what happens in H2O

Isolated heme binds weakly
O2 oxidizes Fe(2) into Fe(3)

11

Oxidized heme

Cannot bind oxygen

12

Heme bound by myoglobin and hemoglobin

Cannot associate with other heme groups
Protein increases heme affinity for O2 and prevents heme from being oxidized

13

Hb binding

Cooperatively (allosteric)

14

Effector or modulator

Allosteric ligand

15

Allostery normally results from

INteractions between subunits in oligomeric proteins

16

Homo vs. heterotropic interactions

Ligands are identical/differ

17

Oxygen type of ligan

Positive homotropic allosteric effector

18

IN metabolically active muscle

Higher Co2 and H+ lead to release of O2
CO2, H+, and BPG Act as negative heterotropic allosteric effectors...BPG also high

19

In alveolar capillaries

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

20

BPG

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

21

Isolated alpha and beta chains

A - like myoglobin...high O2 affinity and not allosteric
B - forms B4 tetramer that is like MB...higher O2 affinity and not allosteric

22

Allosteric properties of Hb from

Interactions between subunits of A2B2 tetramer

23

Quaternary changes upon O2 bidning

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

24

Oxygen binding effect on heme

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

Stabilizes R state relative to T state

25

Mech of negative allosteric effectors

Stabilize the T state
BPG binds in central cavity between the four subunits

26

Fetal hemoglobin

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