Breathing and Exchange of Gases Test - 5

About 70% of CO₂ is converted to bicarbonate ions (HCO₃^-) and transported in plasma. CO₂ diffuses into RBCs, combines with-water and forms carbonic acid {H₂CO₃ ). H₂CO₃ being unstable quickly dissociates Into H⁺ and HCO₃^- . HCO₃^- ions are quite  diffusible. Therefore, HCO₃^-  diffuses from RBCs into the plasma. To maintain the ionic balance CI⁻ ions move from the plasma into the RBCs. This exchange is called chloride shift or Hamburger's phenomenon.
So, the correct answer is 'Hamburger phenomenon'.

The degree of oxygenation of blood markedly affects the amount of CO₂ transported in blood. The lower the PO₂ and the haemoglotion saturation with O₂.
The more the CO₂ that can be carried in the blood. This phenomenon, is called the Haldane effect. It depicts the greater ability of reduced haemoglobin to form carbaminohaemoglobin and to buffer H⁺ by combing with it. In the pulomonary circulation, uptake of O₂ faciliates the release of CO₂ from the pulmonary blood.
The CO₂ transport than the Bohr effect in promoting O₂ transport its results from the simple fact that combination of O₂ with become a stronger acid. This in turn displaces CO₂ form the blood.

The number of RBCs per cubic millimetre of blood is likely to be higher in people living at high altitudes. This is in response to the air being less dense at high altitudes.  Thus, more RBCs (haemoglobin) are needed to absorb the required amount of O₂ from the air.

Although much CO₂ is carried in blood yet blood does not become acidic because of the buffering action of blood. Due to blood buffering, it does not become acidic in spite of the presence of large amount of CO₂. The main buffer present in the body is bicarbonate. Bicarbonate exists in equilibrium with carbonic acid which in turn can be converted to carbon dioxide and water.

Increase in the CO₂ content of the blood decreases the pH of the blood. This decreases the affinity of O₂  with Hb. This is called Bohr effect and is closely related to the fact that deoxygenated Hb binds hydrogen ions more actively than does the Hb. This facilitates gaseous exchange because more O₂ is released in the tissues where the amount of CO₂ is more due to metabolic activity. At the same time, more O₂ is taken up by the lungs or gills when the amount of CO₂ is low.

The iron atom at the center of the haem group of hemoglobin is able to bind O₂, enabling the Hb molecule to carry O₂, from lungs, where PO₂, is high to tissue where PO₂, is less. Carbonic anhydrase, an enzyme present in RBCs, catalyses the reaction between CO₂, and water to form carbonic acid which subsequently dissociates.

This reaction facilitates the transfer of CO₂, from the tissues to the blood and from the blood to the alveoli of the lungs.

Normal puimonary ventilation in an adult human is about 6l per minute and alveolar ventilation is about 4l per minute. Therefore, alveolar ventilation is less than pulmonary ventilation.

Concentration or partial pressure of CO₂(PCO₂ ) is 40 mm Hg in alveolar air and 32 mm Hg in expired air.

Nearly 20-25% of CO₂ is transported by RBCs whereas 70% of it is carried as bicarbonate in plasma. About 7% of CO₂ is carried in a dissolved state through plasma. About 97% of O₂ is carried by RBCs in the blood. About 3% of O₂ is transported in a dissolved state through the plasma.

Excess CO₂ mainly stimulates the respiratory centre of the brain and increase the inspiratory and expiratory signal to the respiratory muscles. O₂ does not have a significant direct effect on the respiratory centre of the brain in controlling respiration.

The thoracic cavity is anatomically an air tight chamber as ft consists of lungs that further consist of air sacs in which the air remains trapped. The contraction of the external intercostal muscles lifts up the ribs and sternum. RBCs transport both O₂ and CO₂. Healthy man can inspire or expire 6000 to 8000 mL of air per minute.

O₂ and CO₂ are exchanged in the alveoli by simple diffusion. The factors that affect the diffusion are pressure gradient of the gases, solubility of the gases and the thickness of the membranes involved in diffusion.

Out of the given options, the processes or steps that are included as parts of the respiration in humans include alveolar diffusion of O₂ and CO₂, transport of gases by blood, and diffusion of O₂ and CO₂ between blood and tissues among others. However, the utilization of CO₂ by cells for catabolic reactions is not considered a part of respiration in humans.

The part ′B′ in the graph represents partial pressure of oxygen.

About 20−25% of CO₂ is carried by Hb as carbamino-haemoglobin. CO₂ reacts directly with amine radicals (NH₂) of Hb of form an unstable compound called carbaminohaemoglobin which releases CO₂ in the lungs.

 About 70% of CO₂ is transported by plasma in the form of bicarbonate ions. When CO₂ enters into the RBCs combines with water, forming carbonic acid (H₂CO₃). H₂CO₃​ is unstable and quickly dissociates into hydrogen ions and  bicarbonate ions. All these reactions are catalyse by the enzym carbonic anhydrase present in RBCs.

The relationship between the partial pressure of O₂ (PO₂) and percentage saturation of the Hb with O₂ is graphically illustrated by a curve called oxygen dissociation curve. The haemoglobin is most saturated with oxygen in the pulmonary vein, as this vein is carrying oxygenated blood from the Iungs towards the left auricle of the heart. From the left auricle the blood moves to the left ventricle where saturation of Hb with O₂ slightly reduces. Vena cava carries deoxygenated blood from all the organs of the body towards right auricle, thus, Hb is less saturated with O₂.

Expiration is normally brought about by the relaxation of inspiratory muscles. Oxyhaemoglobin can hold much less CO₂ in the form of carbaminohemoglobin than what oxyhaemoglobin can. Aperson cannot expel all the air from the lungs even after forceful expiration. The collie of air which remains in the lungs after the most forceful expiration is called residual volume. It is about 1100 L to 1200 mL. A rise in pCO₂ decrease the O₂ affinity of hemoglobin.

Vital capacity is the maximum volume of air a person can breathe in after a forced expiration or the maximum  of air a person can breathe out after a forced expiration. piston. During gaseous exchange the gasses diffuse from high partial pressure to low partial pressure. About 20-25% CO2 is carried by hemoglobin as carbaminohemoglobin. Earthworms respire through the body wall.

Carbon monoxide comobines with Hb far more readily than O₂ (CO has about 200 times greater affinity for Hb as compared to O₂), forming a relativelly stable compound carboxyhaemoglobin. This cause low supply of O₂ to the body cells leading to headache, nausea, dizziness, paralysis and even death.

Hb contains a protein portion called globin and a pigment portion called heam. The heam portion consists of four atoms of iron, each capable of combining with a molecule of O₂, Thus, one Hb carries 4 molecules of O₂

Fetal haemoglobin is the main oxygen transport carrier in human fetus during the last seven months of development in the uterus and persists in the newborn until it is about 6 months old. Functionally, fetal haemoglobin has a higher affinity to bind with oxygen molecules than the adult (or maternal) haemoglobin, giving the developing fetus better access to oxygen from the mother's blood stream.

The exchange of gases in the alveoli of the lungs takes place by simple diffusion. The exchange of gases between the alveoli and blood in the lung is the result of difference in partial pressure of respiratory gases.

When CO₂ concentration in blood increases, breathing becomes faster and deeper. The effect of rising CO₂ concentration is due to decrease in affinity of Hb for O₂. Thus, the CO₂ released in the tissues accelrates the delivery of CO₂ (called Bohr effect). due to which breathing becomes faster and deeper.

About 70% of CO₂ is transported in plasma in the form bof bicarbonates, CO₂ diffuses into RBCs, combines with water and form carbonic acid. Carbonic acid being unstable quickly dissociates into bicarbonate ions and hydrogen ions. This reaction is thousand times faster in RBCs as compared to plasma, as RBCs contain carbonic anhydrase enzyme that reversibe catalyses the conversion of CO₂ and water to carbonic acid.

When temperature decreases, oxy-Hb curve will become more steep. The steep rise of the curve indicates high affinity of Hb for O₂.

Charcoal on burning produces carbon monoxide (CO). CO has about 200 times more affinity for Hb than O₂. On combining with Hb, it forms a stable compound carboxyhaemoglobin. Because of this compound, Hb cannot carry sufficient O₂ to the tissues ultimately leading to death.

The particle pressure of O₂ in the expired air is 116mm Hg. In alveolar air it is 104mm Hg, in arterial blood it is 95mm Hg and in venous blood it is 40mm Hg.

Blood cannot become more than 100% saturated with oxygen. In deep breathing more carbon dioxide is washed out of the blood. This makes oxygen cling more strongly to haemoglobin in red blood cells and therefore oxygen delivery to the tissues is made worse and causes oxygen toxicity. But comparatively, more carbon dioxide levels can improve oxygen delivery. Hence lungs keep carbon dioxide levels high in inhaled air and therefore in the blood.

Blood entering the right side of the heart le., right atrium is a deoxygenated blood having partial pressure of 40 mm Hg. Blood,leaving the right side of the heart i.e., right ventricle will also have almost same partial pressure as the blood is moving from right atrium to right ventricle and also no exchange of gases occurs in this path.