Transportation of oxygen and co2

Ω To explain the mechanism

of transportation of Oxygen &

Carbon Di-oxide in the

body.

OUTLINEo To exp lo re how O2 is t ranspor ted in

the b lood .

o To exp lo re how Co2 is t ranspor ted in

the b lood .

o Th is w i l l i nc lude unders tand ing the

Oxygen & Carbon D i -ox ide d issoc ia t ion

curve .

Oxygen Transport

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Oxygen Transport

Oxygen Transport

Bound to HgbDissolved

Oxygen TransportHaemoglobin molecules can transport up to four O2’s

When 4 O2’s are bound to haemoglobin, it is 100% saturated, with fewer O2’s it is partially saturated.

Oxygen binding occurs in response to the high partial pressure of

Oxygen in the lungs

Co-operative binding: haemoglobin’s affinity for O2 increases as its saturation increases.

Oxygen TransportOxyhemoglobin Formation:

Oxygen + Hb Oxyhemoglobin (Reversible)• I n t h e l u n g s w h e r e t h e p a r t i a l p r e s s u r e o f o x y g e n

i s h i g h , t h e r x n p r o c e e d s t o t h e r i g h t f o r m i n g O x y h e m o g l o b i n

• W h e n o x y g e n b i n d s t o h a e m o g l o b i n , i t f o r m s O X Y H A E M O G L O B I N .

• I n t h e t i s s u e s w h e r e t h e p a r t i a l p r e s s u r e o f o x y g e n i s l o w, t h e r x n r e v e r s e s . O x y H b w i l l r e l e a s e o x y g e n , f o r m i n g a g a i n H b ( o r p r o p e r l y s a i d d e o x y h e m o g l o b i n )

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Oxygen Capacity: The maximum quantity of oxygen that will combine chemically with the hemoglobin in a unit volume of blood

Normal Value: 1.34 ml of O2 per gm of Hb or 20 ml of O2 per 100 ml of blood.

Oxygen Content: how much oxygen is in the blood

Oxygen Saturation : The percentage of all the available heme binding sites saturated with oxygen

Basic Concepts:

T h e o x y g e n - h e m o g l o b i n d i s s o c i a t i o n c u r v e :

Haemoglobin saturation is determined by the partial pressure of

oxygen. When these values are graphed they produce the Oxygen

Disassociation Curve

In the lungs the partial pressure is approximately 100mm Hg at this Partial Pressure haemoglobin has a high affinity to 02 and is 98% saturated.

In the tissues of other organs a typical PO2 is 40 mmHg here haemoglobin has a lower affinity for O2 and releases some but not all of its O2 to the tissues. When haemoglobin leaves the tissues it is still 75% saturated.


Haemoglobin Saturation at High Values

Lungs at sea level: PO2 of 100mmHg haemoglobin is 98% SATURATED

Lungs at high elevations: PO2 of 80mmHg, haemoglobin 95% saturated

Even though PO2 differs by 20 mmHg there is almost no difference in haemoglobin saturation.

When the PO2 in the lungs declines below typical sea level values, haemoglobin still has a high affinity for O2 and remains almost fully saturated.

Factors Affecting Haemoglobin Saturation

Blood acidity…

Blood temperature…

Carbon Dioxide concentration

Factors affecting Disassociation

B LO O D T E M P E R AT U R E

• increased blood temperature• reduces haemoglobin affinity for O2

• hence more O2 is delivered to warmed-up tissue

BLOOD Ph• lowering of blood pH (making blood

more acidic)• caused by presence of H+ ions from

lactic acid or carbonic acid• reduces affinity of Hb for O2

• and more O2 is delivered to acidic sites which are working harder


CARBON D IOXIDE CONCENTRAT ION

• The higher CO2 concentration in tissue• The less the affinity of Hb for O2

• So the harder the tissue is working, the more O2 is released


Bohr Effect• Bohr Effect refers to the

changes in the affinity of Hemoglobin for oxygen.

• I t is represented by shifts in the Hb-O2 dissociation curve

• Three curves are shown with progressively decreasing oxygen affinity indicated by increasing P(50)

SHIFT to the RIGHTDecreased affinity of Hb for Oxygen

Increased delivery of Oxygen to tissues

It is brought about by

1. Increased partial pressure of Carbon Dioxide

2. Lower pH (high [H+])

3. Increased temperature

Ex: increased physical activity, high body temperature (hot weather as well), tissue hypoxia (lack of O2 in tissues)

• SHIFT to the LEFT• Increased affinity of Hb for Oxygen

• Decreased delivery of Oxygen to tissues

• It is brought about by

1. Decreased partial pressure of Carbon Dioxide

2. Higher pH (low [H+])

3. Decreased temperature

• Ex: decreased physical activity, low body temperature (cold weather as well), satisfactory tissue oxygenation

Key Point

• Increased temperature and hydrogen ion (H+) (pH) concentration in exercising muscle affect the oxygen dissociation curve, allowing more oxygen to be uploaded to supply the active muscles.

Carbon Dioxide Transport Method Percentage

• Dissolved in Plasma 7 - 10 %

• Chemically Bound to

Hemoglobin in RBC’s 20 - 30 %

• As Bicarbonate Ion in

Plasma 60 -70 %

Dissolvedbound to HbHCO3-

Carbon Dioxide Transport


Carbaminohemoglobin Formation

• Carbon dioxide molecule reversibly attaches to an amino portion of hemoglobin.

CO2 + Hb HbCO2


Carbonic Acid Formation

• The carbonic anhydrase stimulates water to combine quickly with carbon dioxide.

CO2 + H2 0 H2 CO3


Bicarbonate Ion Formation

• Carbonic acid breaks down to release a hydrogen ion and bicarbonate.

H2 CO3 H+ + HCO-3

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CO2 Transport and Cl- Movement

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This shifts the oxygen-haemoglobin dissociation curve to the right.Thus formation of bicarbonate ion enhances oxygen uploading. Bicarbonate IonsThis also plays a buffering as the H+ is neutralised therefore preventing any acidification of the blood.When blood enters the lungs, where the PCO2 is lower, the H+ and bicarbonate ions rejoin to form carbonic acid, which then splits into carbon dioxide and water. In other words the carbon dioxide is re-formed and can enter the alveoli and then be exhaled. Key PointThe majority of carbon dioxide produced by the active muscles is transported back to the lungs in the form of bicarbonate ions.Carbaminohaemoglobin CO2 transport also can occur when the gas binds with haemoglobin, forming a compound called Carbaminohaemoglobin.It is named so because CO2binds with the amino acids in the globin part of the haemoglobin, rather than the haeme group oxygen does.

EXTRA

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The dissolved carbon dioxide comes out of solution where the PCO2 is low, such as in the lungs.There it diffuses out of the capillaries into the alveoli to be exhaled. Bicarbonate Ions

Bicarbonate IonsCarbon Dioxide and water molecules combine to form carbonic acid (H2CO3).This acid is unstable and quickly dissociates, freeing a hydrogen ion (H+) and forming a bicarbonate ion (HCO3-):CO2 + H2O H2CO3 CO2 + H2O

Bicarbonate IonsThe H+ subsequently binds to haemoglobin and this binding triggers the BOHR effect (mentioned earlier).

EXTRA

Carbon Dioxide

Dissociation CurveHaldane effectFor any given PCO2, the blood will hold more CO2 when the PO2 has been diminished.

Reflects the tendency for an increase in PO2 to diminish the affinity of hemoglobin for CO2.

Mechanism of Haldane effect

Combination of oxygen with hemoglobin in the lungs cause the hemoglobin to becomes a stronger acid. Therefore:

1) The more highly acidic hemoglobin has less tendency to combine with CO2 to form CO2 Hb

2) The increased acidity of the hemoglobin also causes it to release an excess of hydrogen irons.

Interaction Between CO2 and O2

Transportation

1. Bohr effect

2. Haldane effect

Transportation of oxygen and co2

Health & Medicine

Transcript of Transportation of oxygen and co2