L24 Respiration - Transportation of gases

Question 1

What is Dalton’s law?

Answer 1

The total pressure of a mixture of gases is the the sum of thier individual partial pressures.

Question 2

What is the definition of Henry’s law?

Answer 2

Henry’s law is a gas law that describes the relationship between the amount of gas dissolved in a liquid

Question 3

How wouldyou calculate the concentration of a gas dissolved in a solution?

Answer 3

[Gas]dis = s x Pgas

S - solubility coefficient (mM/mmHg)
P - partial pressure of the gas

Use Henry’s law

Question 4

What would happen to the concentration of oxygen if you increase the partial pressure of oxygen?

Answer 4

If PO2 increases then [O2] increases

Question 5

Out of arterial blood and venous blood, which would have a higher [02] dis (dissolved)?

Answer 5

Arterial blood would have a higher concentration of oxygen dissolved in the liquid

Question 6

Oxygen has a relatively low solubility in saline 0.003ml 02 per 100mls of blood per mmHg.

How much would plasma carry under partial pressure of 02 of 100mmHg?

Answer 6

0.3ml O2 per 100mls

Question 7

What is the molecular weight of haemoglobin?

Answer 7

68kD

Haemoglobin has a tetrameric structure with four subunits

Question 8

What does each unit in the haemoglobin consist of?

Answer 8

Each unit consist of a Haem unit and a globin chain

In adult Hg there are:
2 alpha chains and 2 beta chains

Question 9

What is the structure of haemoglobin?

Answer 9

Haemoglobin has a tertameric structure with four subunits.

Question 10

How many chains are there in an adult haemoglobin?

Answer 10

2α chains and 2β chains

Question 11

The haem unit contains a specific atom. What is this atom and its variants?

Answer 11

Haem unit is a porphyrin ring containing a single iron atom. Iron has two states: Fe2+ and Fe3+

Question 12

What happens if the Fe is in a Fe3+ state in haemoglobin?

Answer 12

The enzyme methaemoglobin reductase helps convert any Fe3+ back to Fe2+ so that the oxygen can bind to the iron as it’s in the Fe2+ state

Question 13

What are the two states that haemoglobin exists in? And what does this mean for affinity for O2?

Answer 13

Haemoglobin exists in two states, tense and relaxed.

In tense state, low affinity for O2
In relaxed state, high affinity for O2

Question 14

Why does haemoglobin have a lower affinity for oxygen when in a tensed state?

Answer 14

Haemoglobin in the tense state has a more compact structure, making it less flexible and less able to bind to oxygen

Question 15

What happens to the oxygen- haemoglobin dissociation curve when temperature increases?

Answer 15

The dissociation curve shifts to the right which means that haemoglobin has a decreased affinity for oxygen, and it releases oxygen more readily at a given partial pressure of oxygen

Question 16

What happens to the oxygen- haemoglobin dissociation curve when you make the pH more acidic (lower)?

Answer 16

It shifts to the right. This means that the haemoglobin has a lower affinity for oxygen, and it releases more readily at a given partial pressure of oxygen

CO2 is acidic

Question 17

What is 2,3 Diphpsphoglycerate?

Answer 17

2,3-DPG is a small molecule found in red blood cells that regulate the delivery of oxygen from hemoglobin to tissues

Question 18

What happens to the oxygen- haemoglobin dissociation curve when you increase 2,3 DPG?

Answer 18

An increase in 2,3 DPG shifts oxygen curve to the right. This means that haemoglobin has a decreased affinity for oxygen. This means that it releases oxygen more readily

Question 19

What happens in tissues when respiration is actively being used?

Answer 19

Increased temperature
Increased CO2 production
Decrease in pH

Shifts dissociation curve to the right
Decreased affinity for O2 on haemoglobin - more O2 released to the tissue

Question 20

Why is the Fetal-Hb different to adult-Hb?

Answer 20

The beta globin chains are replaced by the gamma- chains.

Question 21

Why is it essential for fetals to have their beta globin chains replaced by gamma chains?

Answer 21

There is a leftward shift in the Hb-O2 curve - higher affinity for O2 so they can extract oxygen more efficiently for growth and development

Question 22

Why is the ratio between bicarbonate and CO2 important?

Answer 22

The ratio between the two is crucial for maintaining blood pH. The ratio acts as a buffer system, helping to neutralise excess acid or base

Think about balance equation:
CO2 + H2O ↔️ H2CO3 ↔️ HCO3- + H+

Question 23

Where does the carbon dioxide get transported to by the blood (3)?

Answer 23

1) Dissolved in plasma: small portion of CO2 is transported directly and dissolved in the plasma
2) Bound to Hemoglobin: CO2 bind to hemoglobin
3) As bicarbonate ions: Majority of CO2 is transported in the form of bicarbonate ions. CO2 reacts with water to form carbonic acid, which then dissociates into bicarbonate ions and H+ ions by carbonic anhydrase