TRANSPORT

OF

RESPIRATORY

GASES

RESPIRATORY GASES; How are they transported in the blood???

OXYGEN, O2

CARBONDIOXIDE,CO2

The only way for

Oxygen to be carried

around the body

is by the

HEAMOGLOBIN, in

red blood cells.

Carbondioxide is transported by

the blood in three ways;

A)As sodium hydrogencarbonate in plasma

B)As carbomino compounds in red cells

C) In simple solution, dissolved in the plasma

Transport of O2 by the Heamoglobin

Inside red blood cells, there are many heamoglobin molecules which arelarge globular proteins, each consisting of two alpha subunits and two

beta subunits.

beta2beta1

alpha2alpha1

Each subunit has a haem group and a polypeptide globin, This globin molecule coils around the haem groups which contain iron.

Haem group

globin

The iron atom can reversibly bond with one molecule of oxygen. Sinceit has four subunits, a heamoblobin molecule can combine reversibly with

up tofour oxygen molecules forming oxyheamoglobin molecules.

Red BloodCell

Hb + 4O2 HbO8

Transport of O2 by the HeamoglobinWhen an heamoglobin molecule is not bonded to oxygen molecule,

deoxyheamoglobin (heamoglobin without O2 molecules) stays in tensed state.

When the first molecule of oxygen combines with a heamoglobin, oxyheamoglobin shifts to relaxed state in which the shape of heamoglobin changes hence it

becomes easier for other three oxygen molecules to bind to the other haems.

Transport of O2 by the Heamoglobin

The partial pressure of oxygen (pO2) is a measure of oxygen concentration. The amount of oxygen that combines depends upon this partial pressure.

Heamoglobin does not necessarily unload all of its oxygen as it passes through the body tissues.

Heamoglobin requires some conditions in order to load or unload its oxygens.

Partial Pressure of Oxygen, pO2Partial Pressure is the pressure exerted by the one gas in a mixture.

Conditions for heamoglobin to load oxygen

Conditions for heamoglobin to unload oxygen

1 High pO2 Low pO2

2 Low pCO2 High pCO2

3 Alkalinity Inncreased acidity

4 Lower temperature Higher temperature

Transport of O2 by the Heamoglobin

Alveoli

Red blood cell

Respiring cells

Tissue fluid

The tissue fluid surrounds the cells and supplies them with

oxygen. As the cells respire, they produce carbondioxide so the

tissue fluid needs to be replaced continually with the fresh one. In order to supply cells with oxygen,

the red blood cells move to the lungs where there is high pO2 and

increased alkalinity. They combine with the oxygen

molecules and move to the respiring cells where there is high pCO2 and acidity. As a result, they give up their oxygens and oxygen

molecules reach respiring cells via tissue fluid.

Because of the conditions mentioned before, red blood cells

hence heamoglobins are very efficient in transporting oxygen from alveoli in the lungs to the respiring cells in the tissues.

Transport of O2 by theHeamoglobin

The releationship between the partial pressure of oxygen and quantity of the oxygen combined with haemoglobin is shown by S-shaped DISSOCIATION CURVES.

100% saturation means that everyHeamoglobin molecule carries maxOf molecules of oxygen

0% saturation means that none of the

Heamoglobin molecules carry any oxygen

Dissociation curve for an adultHaemoglobin (Hb).

Transport of O2 by theHeamoglobin

As mentioned before, when heamoglobin combines with first oxygen molecule, it alters its shape to anable other molecules to join on it easily. However as heamoglobin starts to become fully saturated, it becomes harder for more oxygen molecules to join.

Dissociation Curve

WHY S-SHAPED?

◊Steep bits in the middle means that it is for oxygen molecules to join the heamoglobin molecules. ◊The shallow parts at each end show that it is harder now for oxygen molecules to be loaded.

Transport of Carbondioxide in the Blood

•Carbondioxide, which is produced in respiration, diffuses from body tissues into the blood where most of it, is taken by the red blood cells.

•In red blood cells,carbondioxide combines with water to form carbonic acid, H2CO3. This reaction is catalysed an enyzme called carbonic anhydrase.

•Then carbonic acid dissociates into hydrogencarbonate and hydrogen ions.

•Hydrogen ions causes oxyhaemoglobin to dissociate. Therefore oxygen diffuses into the cells for respiration.

A)As sodium hydrogencarbonate in plasma

Transport of Carbondioxide in the Blood

Ξ To make sure that red blood cells remain electrically neutral, chloride ionsmove into the red blood cells by a process known as Chloride Shift!

ξ Hydrogencarbonate ions are pumped out of the red blood cells and enter the plasma where they combine with sodium so becoming sodium hydrogencarbonate.

‡ The hydrogen ions combine with haemoglobin and form haemoglobinic acid. This meas that haemoglobin molecules act as buffers mopping up hydrogen ions and preventing changes in pH.

Transport of Carbondioxide in the Blood

B)As carbomino compounds in red cellsCarbon dioxide also reacts with heamoglobin and other proteins to form compounds known as CARBOMINO COPMPOUNDS.

C) In simple solution, dissolved in the plasma

Carbon dioxide is relatively soluble in in the plasma and a small percentage of it is transported in the form of a simple solution, dissolved in the plasma.

Ф BOHR EFFECT Ф

The exact shape of the dissociation curve depends on a number of factors such as

o Partial pressure of carbondioxide (pCO2)o Temperatureo pH

Because of the Bohr Effect, an increase in partial pessure of carbon dioxide, a decrease in pH or increased temperature causes hemoglobin to bind to oxygen with less affinity.

Bohr Effect is very important in respiring tissues since pCO2 increases in tissue fluid. This causes oxyhaemoglobin to release its oxygens readily causing more oxygen to be delivered to the tissues needed for respiration.

Ф BOHR EFFECT Ф

As shown on the dissociationcurve, when carbon dioxidelevel increases, the dissociation curve shifts to right. This prooves that more oxygen is released from the blood. The lower the saturation of O2 in the blood, the more O2 will be released.

Different Species Have Different Dissociation Curves

% saturationof haemoglobin with oxygen

Oxygen tension / kPa

Hawk; an active animal with a highRespiratory rate where there is Plenty of oxygen.

Human

Llama living in Andes; an animalLiving at high attitudes where thePartial pressure of oxygen is lower

Lugworm, animal living in depletedOxygen environment.

Different Species Have Different Dissociation Curves

% saturationof haemoglobin with oxygen

Oxygen tension / kPa

Hawk

HumanLlamaLugworm

As shown on the dissociation curve, the chemical composition of heamoglobin and its oxygen carrying capacity is different in different species.

Organisms living in depleted O2 environment have dissociationcurves to the left of human ones. Eg lugworms and Llamas.

Organisms that are active and have higher partial pressure of oxygen in their environments have curves shifting to right of the human ones. Eg hawks

That means heamoglobins of lugworms have more affinity for oxygen than that of the others’.

Ж SUMMARY Ж

≈ Oxygen molecules are transported in the blood by the heamoglobins in the red blood cells

≈ Carbondioxide molecules are carried by 3 ways; as simple solutions dissolved in plasma, as carbomino compounds and as sodium hydrogencarbonate

≈ The amount of oxygen that binds to heamoglobin molecules depends on partial pressure of oxygen. It is a measure of oxygen concentration.

≈ The dissociation curve shows the releationship between the partial pressure of oxygen and the quantity of oxygen molecules combining with the heamoglobin.

≈ BOHR EFFECT is an effect by which increase in partial pressure of carbondioxide, decrease in pH and high temperature causes a reduction of the affinity of heamoglobin for oxygen.

≈ On the dissocaition curves, the curves shifting to left of the others means increased affinity of oxygen for that heamoglobin.

Main

Points

THE END

Thank You For Listening

Created by Ovgu Ozenli