3.2.8- Transporting Carbon Dioxide

Question 1

What is the chloride shift?

Answer 1

The cc omelet of chloride ions into the erythrocytes to balance the charge as hydrogencarbonate ions leave the cell.

Question 2

Explain what the Bohr Effect is.

Answer 2

The effect that extra Carbon Dioxide has on the haemoglobin, explaining the release of more oxygen.

Question 3

Explain what haemoglobonic acid is.

Answer 3

The compound formed by the buffering action of haemoglobin as it combines with excess hydrogen ions.

Question 4

CO2 is released from _________ __________.

Answer 4

Respiring tissues.

Question 5

Explain the three ways that carbon dioxide is transported from the tissues it’s released from to the lungs for excretion.

Answer 5

5% is dissolved directly in blood plasma/ 10% combines directly with haemoglobin to form a compound called carbaminohaemoglobin/ 85% transported in the form of hydrogencarbonate ions (HCO3-).

Question 6

Carbon dioxide in the blood plasma diffuses directly into where?

Answer 6

Red blood cells.

Question 7

When carbon dioxide from the blood plasma has diffused into RBC’s, what happens here?

Answer 7

It combines with water to form carbonic acid- this is catalyses by carbonic anhydrase.

Question 8

What is the chemical symbol for carbonic acid?

Answer 8

H2CO3.

Question 9

Once carbonic acid has been made in red blood cells, what two things does it dissociate into?

Answer 9

Hydrogen ions (H+) and Hydrogencarbonate ions (HCO3-).

Question 10

Once carbonic acid has dissociated into hydrogen and hydrogencarbonate ions, what happens?

Answer 10

HCO3- ions defuse out of the red blood cell and into the plasma. The charge in the RBC is maintained by the chloride shift into the RBC’s.

Question 11

As hydrogencarbonate ions move out of the red blood cell, how is the charge inside the cell maintained?

Answer 11

The chloride shift of Chloride ions (Cl-) ions into the red blood cell.

Question 12

Why may the inside of a red blood cell become acidic?

Answer 12

As hydrogen ions (H+) build up in the red blood cell as hydrogencarbonate ions move out of the cell.

Question 13

Explain how the red blood cell is prevented from becoming acidic as hydrogencarbonate ions leave the cell, leaving a build up of H+ ions.

Answer 13

The H+ ions are taken out of solution by associating with haemoglobin to produce haemoglobonic acid (HHb)- the haemoglobin acts as a buffer.

Question 14

Explain the sequence of events that take place for the formation of hydrogencarbonate ions and the transportation of CO2.

Answer 14

CO2 diffuses into RBCs/ CO2+ H2O (cat by carbonic anhydrase)= H2CO3- carbonic acid/ carbonic acid dissociates to H+ and Hydrogencarbonate (HCO3-) ions/ HCO3- ions diffuse out of RBC to plasma- charge maintain as chloride shift inside RBCs takes place/ H+ ions associate with haemoglobin to be taken out of solution to stop the cell becoming acidic- forms Haemoglobonic acid (HHb).

Question 15

Define what carbonic anhydrase is.

Answer 15

The enzyme that catalyses the combination of carbon dioxide and water.

Question 16

Blood entering respiring tissues carries oxygen as ___________.

Answer 16

Oxyhemoglobin.

Question 17

Compare the partial pressure (AKA oxygen tension) in the lungs and respiring tissue.

Answer 17

The oxygen tension is lower in the respiring tissue in the lungs.

Question 18

Why is the oxygen tension lower in the respiring tissues than the lungs?

Answer 18

Oxygen has been used for respiration.

Question 19

Explain what effect the lower oxygen tension in the respiring tissues than in the lungs will have on the oxyhemoglobin.

Answer 19

It means the oxyhemoglobin will begin to dissociate, leaving haemoglobin available to take up H+ ions to form haemoglobonic acid. Where the tissues are very active, more CO2 is released

Question 20

Describe the sequence of events that explains how CO2 effects haemoglobin and what this will cause.

Answer 20

CO2 enters RBCs and forms carbonic acid that dissociates to release H+ ions/ H+ ions make the he Cytoplasm more acidic/ the acidity affects the tertiary structure of the haemoglobin (as it’s a protein) and reduces its affinity for oxygen/ haemoglobin can’t hold as much oxygen- oxygen dissociates from oxyhemoglobin to respiring tissues.

Question 21

Explain how the demand for more oxygen at tissues that respite more (eg contracting muscle) is met.

Answer 21

There will be more CO2 here, resulting in more H+ ions being produced in the RBC’s, therefore making the oxyhemoglobin release more oxygen by dissociation.

Question 22

When there is more CO2 present, the haemoglobin becomes ______ _______ with oxygen.

Answer 22

Less saturated.

Question 23

What is the Bohr Shift?

Answer 23

The shift downwards and to the right of the haemoglobin dissociation curve that reflects how haemoglobin becomes less saturated with oxygen the more CO2 is present.

Question 24

Explain how the Bohr Effect helps to create a balance In cells.

Answer 24

It results in more oxygen being released where more CO2 is produced in respiration- just what muscles need for aerobic respiration to continue.