Transport of Blood Gases PDF

TRANSPORT OF BLOOD GASES Dr. Berrak YEĞEN 2020  Objectives: comprehend how oxygen is carried in blood list the factors that affect the binding of O2 with hemoglobin explain the characteristics of oxygen- hemoglobin dissociation curve comprehend how carbon...

TRANSPORT OF BLOOD GASES Dr. Berrak YEĞEN 2020  Objectives: comprehend how oxygen is carried in blood list the factors that affect the binding of O2 with hemoglobin explain the characteristics of oxygen- hemoglobin dissociation curve comprehend how carbon dioxide is carried in blood  Transport of Oxygen Normally 97 % in combination with hemoglobin (oxyhemoglobin; Hb-O2) Remaining 3 % in the dissolved state in the plasma Each of the 4 iron atoms can bind (reversible) one O2 molecule.  Transport of Oxygen O2 molecule combines loosely and reversibly with the heme portion of the Hb When PO2 is high, as in the pulmonary capillaries, oxygen binds with the Hb; O2 but when the PO2 is low, as in the tissue capillaries, oxygen is released from Hb. O2  Oxygen binding Reaction of O2-binding is an oxygenation, not an oxidation. Hb4 Hb4O8 --- each unit binds one O2 molecule --- very rapid oxygenation (0.01 sec) --- deoxygenation is also very rapid both oxygenation and deoxygenation are very rapid  Quaternary structure of Hb sigmoindal sahpe of oxygen biniding curve is beacuse of hb quaternay structure serves for its affinity for O2 by shifting the relationship of four components (polypeptide chains), the molecule helps in either O2 uptake or O2 delivery  Affinity When Hb takes up a small amount of O2 - additional uptake of O2 is facilitated. Hb’s first heme binds with O2  - ↑ affinity of the 2nd heme to combine with O2 - oxygenation of the 2nd  ↑ affinity of the 3rd. explains the sigmoid shape of the O2-Hb dissociation curve The O2-Hb Dissociation Curve  The O2-Hb Dissociation Curve The percentage of Hb that is bound with O2 increases progressively as the PO2 increases “the percent saturation of the hemoglobin” Sigmoid shaped curve * 60 - 100 mm Hg: saturation does not differ much between 3000 m * changing PO2 below 60 mm Hg: curve is very steep, larger release of O2 to the tissues. po 45 mmhg 4500 mmhg Myoglobin curve is hyperbolic; only one O2 molecule per one myoglobin molecule  Binding/releasing involves breaking or forming salt bridges between polypeptide chains. Upon oxygenation, 2  chains move closer; while upon deoxygenation, they move apart. These shifts are essential for the change in affinity and they occur nearly 108 times during the life span of a RBC. which one of the sentances below is in correct about hb sturcutre /? hb has a sigmoid curve due tto its quatery structure myoglobin has a hpercanic stircture when hb is oxgenated the b chains are far from each other  Maximum amount of O2 that can be bound to Hb When blood is equilibrated with 100 % oxygen  Hb is 100 % saturated In the blood of a normal person- * each g of Hb can bind 1.34 ml of O2 * 15-16 g of Hb/100 ml of blood Hb in 100 ml of blood can combine with (16 x 1.34 =21 ml) nearly 20 ml of O2, when Hb is 100% saturated: “20 volumes percent”  O2 In systemic arterial blood, PO2 is about 95 mm Hg; O2 saturation is saturation about 97 %  19.8 ml of O2 / dl In normal venous blood returning from the tissues, PO2 is 40 mm Hg; saturation of Hb is about 75 %  14.6 ml of O2 /dl  Utilization coefficient whichone of below is right about o2 satruration The fraction of blood that gives off its O2 as it passes through the tissue capillaries normal is 25 % (1/4th) During heavy exercise  rises to 75 % to 85 % O2 In local tissue areas, * the blood flow is very slow or * the metabolic rate is very high, approaches 100 %- all O2 is removed O2 O2 O2 The O2-Hb P50 is the PO2 at which the Hb is half saturated with O2. Dissociation Curve P50 27 mmHg The O2-Hb Dissociation Curve Affinity? higher P50 lower affinity of Hb for O2.  Bohr effect When the blood becomes - * slightly acidic (pH 7.4 to 7.2) shifts to the right. * affinity of Hb for O2 ; O2 is released With an increase in pH  a shift to the left Shift of OHDC by changes in blood CO2 and hydrogen ions enhances the release of O2 from the blood in the tissues The decrease in O2 affinity of Hb when the pH of blood falls or CO2 increases  BoH+R effect  CO2 In Lungs CO2 diffuses from the blood into the alveoli O2 reduces PCO2 and decreases H+ ion (decreased blood carbonic acid) - shift of the OHDC to the Left and upward - the amount of O2 that binds with Hb at any given alveolar PO2 becomes increased, -allowing greater O2 transport to the tissues  In tissue capillaries CO2 entering the blood from the tissue shifts the curve rightward (P50 increased), displacing O2 from the Hb and delivers to the tissues at a higher PO2. CO2 O2 Factors that shift the curve to the Right 1. increased CO2 and decreased pH 2. increased blood temperature 3. increased 2,3-diphosphoglycerate Which of the following factors can shift the oxygen-hemoglobin dissociation curve to the right (decreasing hemoglobin affinity for oxygen)? a) High blood pH (alkalosis) b) Low blood temperature c) Increased carbon dioxide concentration d) Presence of fetal hemoglobin Factors that shift the curve to the Left 1. presence of large quantities of fetal Hb (for O2 delivery to fetal tissues –hypoxic- from adult Hb) 2. carbon monoxide poisoning  Effect of 2,3- Diphosphoglycerate produced from 3-phosphoglyceraldehyde (glycolysis via Embden-Meyerhof pathway) * highly charged anion * binds to  chains * 1 mole of deoxyHb binds one mole of 2,3-DPG Normal DPG in the blood keeps the OHDC slightly shifted to the right all the time  During exercise muscles release large quantities of CO2 acids released by the muscle, [H+]  temperature of the muscle increases 2 or 3o C DPG increases together shift the muscle capillary blood to the right (P50 increases)  In hypoxic conditions RBC DPG increases (