Transport of gases in the blood

Physiology, Human Health Edition 9, Respiration, easy to understand with pictures. Oxygen and carbon dioxide are transported in two forms: physical dissolution and chemical combination. Among them, chemical combination is the main form, and physical dissolution accounts for a very small proportion. However, physical dissolution is chemical combination. premise.

Edited at 2024-02-08 16:30:16

PlotWizard

Recent works View more works>>

Transport of gases in the blood

PlotWizard

Recent works View more works>>

Recommended to you
Outline

Transport of gases in the blood

Overview

Both oxygen and carbon dioxide are transported in two forms: physical dissolution and chemical combination. Chemical combination is the main form, and physical dissolution accounts for a very small proportion. However, physical dissolution is the prerequisite for chemical combination.

1. Oxygen transport

Oxygen is mainly transported in the form of chemical combinations, and physical dissolution accounts for a very small proportion.

(1) Molecular structure of hemoglobin (Hb)

The Hb molecule is composed of 1 globin and 4 hemes. The center of each heme group is a divalent iron, which can combine with oxygen, making Hb a (bright red) oxyhemoglobin (HbO2), which does not bind oxygen. Hb is called (blue-purple) deoxygenated hemoglobin (Hb).

The four monomers of Hb are connected by salt bonds between each other and within the subunits. The combination or separation of Hb and O2 will affect the formation and breakage of salt bonds

(2) Characteristics of the combination of Hb and O2

1. The binding reaction is rapid and reversible

The combination of Hb and oxygen is affected by the partial pressure of oxygen

2. The binding reaction is oxygenation rather than oxidation

The combination of ferrous iron and oxygen is not accompanied by a change in the valence of iron ions

3.The amount of Hb combined with O2

1 molecule of Hb can bind 4 molecules of O2

(1) Hb oxygen capacity: refers to the maximum amount of O2 that Hb can combine with in 100ml of blood

(2) Hb oxygen content: refers to the amount of O2 actually combined with Hb in 100ml of blood

(3) Hb oxygen saturation: refers to the percentage of Hb oxygen content and Hb oxygen capacity

4. The oxygen dissociation curve is S-shaped.

The S-type is related to the allosteric effect of Hb. The four subunits of Hb have a synergistic effect with each other, that is, after one subunit binds to O2, the other subunits are more likely to bind to O2 due to the allosteric effect; conversely, when one subunit of HbO2 releases O2, Other subunits are more likely to release O2

(3) Oxygen dissociation curve

(4) Factors affecting the oxygen dissociation curve

Influencing factors include blood pH and PCO2, temperature, and 2,3-bisphosphoglycerate (2,3-DGP) in red blood cells.

Effect of carbon monoxide on oxygen dissociation curve

After inhaling a large amount of carbon monoxide, CO can combine with Hb to form carbon monoxide hemoglobin, occupying the O2 binding site in the Hb molecule. During carbon monoxide poisoning, the patient's lips turned cherry color. Carbon monoxide poisoning is currently treated with hyperbaric oxygen therapy.

2. Transport of carbon dioxide

(1) Transport forms of CO2

Physical dissolution (5%)

Chemical bonding (95%)

1. Bicarbonate (88%)

The reaction is reversible and both require carbonic anhydrase. The direction of the reaction depends on the level of PCI2. In tissues, the reaction proceeds to the right; in the lungs, the reaction proceeds to the left.

A small part of HCO3- combines with K and transports CO2 in the form of KHCO3. Most of the HCO3- diffuses through the red blood cell membrane and enters the plasma along the concentration gradient, thus reducing the negative ions in the red blood cells. On the other hand, red blood cells do not allow positive ions to pass through, but allow small negative ions to pass through, so Cl- enters red blood cells from plasma through the unique HCO3--Cl- exchanger on the red blood cell membrane. This phenomenon is called Cl- transfer

2. Carbamoyl hemoglobin (HbCO2) (7%)

This reaction does not require enzyme catalysis and is rapid and reversible. The main influencing factor is oxygenation

(2) CO2 dissociation curve

(3) Factors affecting CO2 transport

Whether Hb is combined with O2 is the main factor affecting CO2 transport

Holden effect

The combination of Hb and O2 can promote the release of CO2, and after releasing O2, Hb can easily combine with CO2.