1 / 11

Hemoglobin

Hemoglobin. Carrier of oxygen in blood. Hemoglobin. Tetrameric two pairs of globins, Hb  and Hb  carried by erythrocytes denucleated (no organelles), “biconcave” 120 day lifespan Typically 96% loaded with oxygen in arteries, 64% returning to heart. fig 7-3. fig 7-6.

benard
Télécharger la présentation

Hemoglobin

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Hemoglobin Carrier of oxygen in blood

  2. Hemoglobin • Tetrameric • two pairs of globins, Hb and Hb • carried by erythrocytes • denucleated (no organelles), “biconcave” • 120 day lifespan • Typically 96% loaded with oxygen in arteries, 64% returning to heart

  3. fig 7-3

  4. fig 7-6

  5. Cf. Hb subunits and Mb • Primary structure of Hb and Hb less than 50% homologous • Secondary and Tertiary Structures of Hb and Hb very similar • Hb’s and Mb identical at 27 positions • Secondary and Tertiary Structures of Mb and Hb subunits very similar

  6. fig 7-7

  7. Quaternary Structure of Hb • Contact between 1 and 1 very strong, involves 30 residues (mostly hydrophobic interaction) • Contact between 1 and 2 weaker, involves <20 residues • Can be dissociated (urea) into  units.

  8. T and R states of Hb • Affinity for O2 higher in R (“Relaxed”) state • T (“Tense”) state more stable • More ion pairs, mostly between 1 and 2 and vice-versa • Binding oxygen causes T  R • Fe2+ moves back, F8 moves, cascade of residue movements

  9. T  R transition • Movement of residues causes subtle changes in optimum interfacial arrangements • In effect, Hb closes up (think of the relaxation of letting air out) • Subunit structures do not change much, just quaternary structure

  10. pO2 • Concentration in blood in lungs – 13.3 kPa • Concentration in blood in tissues – 4 kPa Hb must tend to bind O2 in lungs, but release O2 in tissues

  11. Function of Hb • Cooperativity • As more O2 is bound, T  R • The binding of O2 by one subunit affects the binding of O2 of the molecule. • In effect, the equilibrium constant changes as O2 is bound; the binding curve is not hyperbolic, but rather sigmoidal.

More Related