CO2 Transport | Carbon-di-oxide Transport | Respiratory Gas Exchange | Respiratory Physiology

Summary

This Bite Size Med video explains carbon dioxide transport in the blood. Carbon dioxide, a byproduct of tissue metabolism, is transported in three forms: dissolved (5%), bound to hemoglobin as carbaminohemoglobin (20%), and chemically modified as bicarbonate (70%). The video highlights the Bohr and Haldane effects, which regulate oxygen and carbon dioxide exchange. It also details the role of carbonic anhydrase in forming carbonic acid, the chloride shift, and how oxygenation of hemoglobin promotes carbon dioxide release for expiration.

Takeaways

• 🌟 The purpose of respiration is gas exchange, where oxygen enters the bloodstream and carbon dioxide is expelled.
• 🔍 Carbon dioxide in the pulmonary capillaries originates from mixed venous blood, which carries waste from body tissues.
• 🏃‍♂️ Tissue metabolism produces carbon dioxide as a byproduct when using oxygen.
• 💧 Dissolved carbon dioxide constitutes about 5% of its transport in the blood, being more soluble than oxygen.
• 🩸 The bound form of carbon dioxide is carbaminohemoglobin, accounting for approximately 20%, and it affects oxygen binding.
• 🔄 The Bohr effect describes how carbon dioxide binding to hemoglobin reduces its oxygen affinity, shifting the oxygen dissociation curve rightward.
• 🔄 The Haldane effect explains how the removal of oxygen from hemoglobin increases its affinity for carbon dioxide.
• 🧪 The most significant form of carbon dioxide transport is chemically modified as bicarbonate ions, about 70%.
• 🔄 Carbon dioxide reacts with water in the presence of carbonic anhydrase to form carbonic acid, which then dissociates.
• 🔄 The chloride-bicarbonate exchange, or chloride shift, maintains ionic balance as bicarbonate leaves red blood cells for chloride.
• 💡 Hemoglobin buffers hydrogen ions to prevent an acidic environment and maintains blood pH.

Q & A

What is the primary purpose of respiration?

The primary purpose of respiration is gas exchange, where oxygen enters the capillary from the alveolus and carbon dioxide leaves the capillary to enter the alveolus and is then breathed out.

Where does the carbon dioxide in the pulmonary capillaries come from?

The carbon dioxide in the pulmonary capillaries comes from mixed venous blood that arrives via the pulmonary artery, which in turn receives blood from all the body tissues.

How is carbon dioxide produced in the body?

Carbon dioxide is produced during tissue metabolism, where tissues use oxygen and form carbon dioxide as a byproduct.

In what three forms is carbon dioxide transported in the blood?

Carbon dioxide is transported in the blood in three forms: dissolved carbon dioxide, bound form as carbaminohemoglobin, and chemically modified form as bicarbonate.

What percentage of carbon dioxide is transported as dissolved carbon dioxide?

About five percent of carbon dioxide is transported as dissolved carbon dioxide, which is more soluble than oxygen.

How does carbon dioxide bind to hemoglobin and what is the effect on oxygen affinity?

Carbon dioxide binds to hemoglobin at the n-terminus of the globin chain, forming carbaminohemoglobin. This binding reduces hemoglobin's affinity for oxygen, which is known as the Bohr effect.

What is the Haldane effect and how does it relate to oxygen and carbon dioxide binding to hemoglobin?

The Haldane effect is the phenomenon where the binding of oxygen to hemoglobin lowers its affinity for carbon dioxide. Conversely, if less oxygen is bound, there's a higher affinity for carbon dioxide.

What is the most important form in which carbon dioxide is transported in the blood and what percentage does it represent?

The most important form in which carbon dioxide is transported is as bicarbonate, accounting for around 70 percent of its transport in the blood.

How does the chloride shift or anion exchange protein Band 3 contribute to carbon dioxide transport?

The chloride shift, facilitated by the anion exchange protein Band 3, allows bicarbonate to leave the red blood cell to maintain ionic balance, and chloride enters in exchange, which is crucial for the transport of carbon dioxide.

How does hemoglobin buffer hydrogen ions to maintain blood pH?

Hemoglobin buffers hydrogen ions to prevent an acidic environment, thus maintaining the pH of the red blood cells and blood. This is important for the proper functioning of the blood's transport mechanisms.

What happens to carbon dioxide in the pulmonary capillaries during oxygenation of hemoglobin?

During oxygenation of hemoglobin in the pulmonary capillaries, hydrogen ions dissociate from hemoglobin, and bicarbonate enters the red blood cell in exchange for chloride. This leads to the formation of carbonic acid, which then dissociates into carbon dioxide and water, with carbon dioxide being exhaled.

How does the concentration of carbon dioxide in the blood depend on tissue metabolism and alveolar ventilation rate?

The concentration of carbon dioxide in the blood depends on the rate of its production through tissue metabolism and the rate at which it is expired through alveolar ventilation.

Outlines

00:00

🌬️ Carbon Dioxide Transport in Blood

This paragraph discusses the process of carbon dioxide transport in the blood. It begins by explaining the purpose of respiration, which is gas exchange. Oxygen enters the bloodstream from the alveolus, while carbon dioxide exits the bloodstream into the alveolus to be exhaled. The script then traces the origin of carbon dioxide to tissue metabolism, where it is produced as a byproduct of oxygen use. The transport of carbon dioxide is detailed in three forms: dissolved in the plasma (5%), bound to hemoglobin as carbaminohemoglobin (20%), and chemically modified as bicarbonate (70%). The binding of carbon dioxide to hemoglobin is explained, along with the Bohr and Haldane effects, which describe the interplay between oxygen and carbon dioxide binding to hemoglobin. The paragraph concludes with a description of how carbon dioxide is converted to bicarbonate in red blood cells through the action of carbonic anhydrase, and how this bicarbonate is exchanged for chloride ions to maintain ionic balance, a process known as the chloride shift.

Keywords

💡Respiration

Respiration is the process by which living organisms exchange gases, primarily oxygen and carbon dioxide. In the context of the video, respiration refers to the inhalation of oxygen and the exhalation of carbon dioxide. It is essential for life as it allows for the delivery of oxygen to cells and the removal of carbon dioxide, a waste product of cellular metabolism.

💡Carbon Dioxide

Carbon dioxide (CO2) is a colorless, odorless gas that is a byproduct of cellular respiration. In the video, it is discussed as a key component in the gas exchange process, where it is transported from the body's tissues to the lungs to be exhaled.

💡Capillary

Capillaries are the smallest blood vessels that connect arteries and veins. They play a crucial role in the exchange of gases, nutrients, and waste products between blood and tissues. The video mentions that oxygen enters the capillary from the alveolus and carbon dioxide leaves the capillary to enter the alveolus.

💡Alveolus

The alveolus is a tiny air sac in the lungs where gas exchange occurs. Oxygen from the air we breathe in diffuses into the bloodstream through the alveoli, and carbon dioxide from the blood diffuses into the alveoli to be exhaled. The video emphasizes the role of the alveolus in the transport of carbon dioxide.

💡Tissue Metabolism

Tissue metabolism refers to the chemical processes that occur within body tissues to maintain life. These processes require oxygen and produce carbon dioxide as a waste product. The video explains that carbon dioxide in the pulmonary capillaries originates from tissue metabolism.

💡Hemoglobin

Hemoglobin is an iron-containing molecule in red blood cells that binds to oxygen and carbon dioxide. The video discusses how carbon dioxide binds to hemoglobin at a different site than oxygen, forming carbaminohemoglobin, which is part of the transport process of carbon dioxide in the blood.

💡Bohr Effect

The Bohr effect describes how the binding of carbon dioxide to hemoglobin reduces its affinity for oxygen, causing a shift in the oxygen dissociation curve to the right. This effect is important for ensuring that oxygen is released to the tissues where it is needed, as explained in the video.

💡Haldane Effect

The Haldane effect is the increased affinity of hemoglobin for carbon dioxide when oxygen is removed. This is crucial for the pickup of carbon dioxide by hemoglobin in tissues, as detailed in the video script.

💡Bicarbonate

Bicarbonate is a form of carbon dioxide that is chemically modified and transported in the blood. The video explains that about 70% of carbon dioxide is transported as bicarbonate, which is formed when carbon dioxide reacts with water in the presence of carbonic anhydrase.

💡Chloride Shift

The chloride shift, also known as the chloride-bicarbonate exchange, is a process where chloride ions move into red blood cells in exchange for bicarbonate ions to maintain ionic balance. This is part of the mechanism by which carbon dioxide is transported in the blood, as described in the video.

💡Carbonic Anhydrase

Carbonic anhydrase is an enzyme that catalyzes the formation of carbonic acid from carbon dioxide and water. This enzyme plays a key role in the chemical modification of carbon dioxide to bicarbonate in red blood cells, as discussed in the video.

Highlights

Respiration's purpose is gas exchange, with oxygen entering the capillaries from the alveolus and carbon dioxide leaving to be exhaled.

Carbon dioxide in the pulmonary capillaries originates from mixed venous blood, which comes from the pulmonary artery.

Carbon dioxide is a byproduct of tissue metabolism where tissues use oxygen and produce carbon dioxide.

Transport of carbon dioxide occurs in three forms: dissolved, bound to hemoglobin, and chemically modified.

Dissolved carbon dioxide makes up about 5% of the total carbon dioxide in the blood.

Carbon dioxide is more soluble than oxygen, hence its higher percentage in dissolved form.

Bound carbon dioxide forms carbaminohemoglobin, accounting for about 20% of carbon dioxide transport.

Carbon dioxide binds to hemoglobin at a different site than oxygen, at the n-terminus of the globin chain.

Binding of carbon dioxide to hemoglobin reduces its affinity for oxygen, causing a rightward shift in the oxygen dissociation curve (Bohr effect).

The Haldane effect describes how the removal of oxygen from hemoglobin increases its affinity for carbon dioxide.

The most significant form of carbon dioxide transport is as bicarbonate, accounting for approximately 70%.

Carbon dioxide from tissues diffuses into capillaries, binds to water, and forms carbonic acid through carbonic anhydrase in red blood cells.

Bicarbonate ions leave red blood cells to maintain ionic balance, and chloride ions enter in a process known as the chloride shift.

Hemoglobin buffers hydrogen ions to prevent an acidic environment and maintain blood pH.

In the lungs, oxygenation of hemoglobin promotes the dissociation of hydrogen ions, allowing bicarbonate to re-enter red blood cells.

The formation of carbonic acid from bicarbonate and hydrogen ions leads to the production of carbon dioxide and water, which is then exhaled.

The concentration of carbon dioxide in the blood is determined by tissue metabolism rate and alveolar ventilation rate.

The video provides a comprehensive journey of how carbon dioxide moves from tissues to the lungs.

Transcripts

hi everyone welcome to bite size med

where we talk about quick

bite-sized concepts in basic medical

sciences for study and rapid review

this video is on carbon dioxide

transport in blood

the purpose of respiration is gas

exchange

oxygen enters the capillary from the

alveolus

and carbon dioxide leaves the capillary

to enter the alveolus

and then get breathed out the oxygen

comes from the atmosphere

but where does the carbon dioxide come

from

if we backtrack it carbon dioxide in the

pulmonary capillaries

is from mixed venous blood that comes

from the pulmonary artery

which came off the right heart receiving

blood from all the body tissues

so carbon dioxide is formed during

tissue metabolism

the tissues use oxygen and form carbon

dioxide

the transport of carbon dioxide from the

tissues

through systemic circulation and then

pulmonary circulation

happens in three forms as dissolved

carbon dioxide

a bound form and a chemically modified

form

dissolved carbon dioxide is around five

percent

carbon dioxide is more soluble than

oxygen

so it dissolves more and that's why it's

five versus oxygen which was at just two

percent

the bound form is with hemoglobin as

carb amino hemoglobin

this is around 20 percent carbon dioxide

binds to hemoglobin

at a different site than oxygen the

n-terminus of the globin chain

the binding of carbon dioxide to

hemoglobin reduces

its affinity for oxygen shifting the

oxygen dissociation curve to the right

this is the bohr effect the binding of

oxygen to hemoglobin

lowers the affinity for carbon dioxide

so if less oxygen is bound that means

there's a higher affinity for carbon

dioxide

and this is the haldane effect

so let's see how these work together

the tissue produces carbon dioxide that

binds to hemoglobin

reducing the affinity for oxygen and

shifting the oxygen dissociation curve

to the right

so more oxygen is released to the

tissues

that was the bohr effect

now the removal of oxygen from

hemoglobin

increases hemoglobin's affinity for

carbon dioxide

for the carbon dioxide that the tissues

have produced

and that's the haldane effect

that was the bound form the most

important form in which carbon dioxide

gets transported is chemically modified

as bicarbonate

around 70 percent

the carbon dioxide from the tissues

diffuses into the capillaries

it binds to water and by carbonic

anhydrase in the rbcs

it forms carbonic acid that then

dissociates into a hydrogen ion and a

bicarb ion

now these reactions are reversible

the bicarbonate leaves the rbc to

maintain ionic balance

a negative ion enters that's chloride

this is by the anion exchange protein

that's the band

3 protein and this is the chloride

bicarbonate exchange

also called a chloride shift

if the hydrogen ions were to remain as

such

it would create an acidic environment so

it gets buffered by hemoglobin

that maintains the ph of the rbc and the

blood

now the bicarbonate is in the plasma and

the hydrogen ions have been buffered by

hemoglobin

they travel to the lung and reach the

pulmonary capillaries

here oxygen is diffusing from the

alveolus into the capillary

the oxygenation of hemoglobin promotes

dissociation of the hydrogen ions from

hemoglobin

because hemoglobin wants to take up

oxygen

the bicarbonate enters the rbc in

exchange for chloride

so now hydrogen ions bind to bicarb ions

and by carbonic anhydrase they form

carbonic acid

which then dissociates into carbon

dioxide and water

and the carbon dioxide gets breathed out

so the oxygenation of hemoglobin shifts

this reaction

towards the formation of carbon dioxide

for expiration

so the carbon dioxide concentration in

blood

depends upon how much is produced that's

the tissue metabolism rate

and how much is expired that's the

alveolar ventilation rate

and that is the journey that carbon

dioxide takes from the tissues to the

lungs

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