Transport Of Gases

Question 1

What % of oxygen is carried bound to Hb from the alveoli to the tissues down pp

Answer 1

98% (2% is dissolved in plasma)

Question 2

How many oxygens bind to the heme groups (fe and porphyrin)

Answer 2

4 = hb4o2

Question 3

Which 4 things affect Hb saturation

Answer 3

Ph

Co2

Temp

23 BPG

Question 4

What saturation do Hb have at high pp02 (100 in the alveoli)

Answer 4

97.5%

Question 5

What happens to saturation at tissues with ppo2 which is low (40 at rest)

Answer 5

20-35% dissociation

The Hb is much less saturated at around 70% at low ppo2

Question 6

Tissues which are respiring / exercise have lower than 40mmhg po2, what happens to dissociation/ saturation

Answer 6

85% of the oxygen becomes dissociated from Hb

Delivers o2 to the tissues

Question 7

Why is ph / co2 high in the tissues which affects dissociation

Answer 7

Tissues are respiring producing co2 which is then converted to H to decrease ph

Question 8

What happens if there is high pco2 eg at the tissues

Answer 8

Saturation decreases

Faster dissociation of o2 from the Hb

Question 9

What would a lower ph (H+ presence due to co2) cause

Answer 9

Faster dissociation of o2 from Hb

ensures o2 to respiring tissues

Question 10

Explain the steps of how co2 diffusion into rbc at high pco2 eg at tissues causes oxygen dissociation

Answer 10

Co2 presence will react with h20

Forms H2co3 (carbonic acid) - VIA CARBONIX ANHYDRASE

this splits into H+ and HCO

H+ binds to Hb to form HHb

This displaces o2 and o2 can diffuse into tissues

Question 11

How does H binding to Hb cause oxygen dissociation

Answer 11

Hb becomes in the Taut state at high pco2 / H

This causes dissociation of oxygen to tissues

Question 12

What is the effect of co2 and H called on oxygen dissociation

Answer 12

Bohr effect

Question 13

What happens to the Hco3 produced by co2 diffusion into rbc at high pco2 levels

Answer 13

Diffuses into the blood/ plasma

Question 14

When does temp increase

Answer 14

During exercise

Question 15

How does temp affect dissociation

Answer 15

Increased temp due to exercise increases dissociation of o2 to tissues

Question 16

How does 2,3 DPG affect dissociation

Answer 16

High 2,3 DPG causes faster dissociation

Question 17

How does dpg cause dissociation

Answer 17

Interacts with B chains and causes 02 dissociation

Question 18

When would high dpg be needed

Answer 18

In people with hypoxia / low o2

Increases their dissociation

Eg anemia, at high altitudes (low po2)

Question 19

How is Hbf different in dissociation

Answer 19

Much higher affinity/ saturation at every po2 than normal maternal dissociation curve

Question 20

What happens in anemia to cause low o2 levels

Answer 20

They have small / non working rbc with low o2 capacity

Even if saturated

Always much lower o2 content

Question 21

Does dpg cause dissociation in foetal hbf?

Answer 21

No

Question 22

How much of co2 is dissolved in plasma from tissues

Answer 22

7%

Question 23

Other than dissolved co2, how else is co2 transported to alveoli

Answer 23

As HCO3 (70%)

Or

As Hb co2 (carbaminohaemoglobin) (23%)

Question 24

How is Hco3 produced and then transported to alveoli (bicarbonate)

Answer 24

Co2 diffuses into rbc from tissues

Reacts with h20 to form H2co3

Splits into H and Hco3

H binds onto the HHb whereas Hco3 diffuses into plasma to be transported

Question 25

How is co2 later diffuses into alveoli

Answer 25

The 70% Hco3 binds with the H from HHb to form H2co3 (carbonic acid)

H2co3 converts to co2 and water and co2 diffuses into alveoli

Some co2 also from the dissociation of 23% hb co2 (carbamino haemoglobin)

7% diffused co2 diffuses straight to alveoli

Question 26

At high pco2 what happens to carbonic anhydrase action

Answer 26

Converts the co2 and water to H2co3 forming Hco3 70%

Question 27

Why would Hbco2 cause o2 dissociation as well as HHb would

Answer 27

Because it also favours the T state

Question 28

Why does the production of co2 ie from HCO and H or the opposite reaction be slower in plasma than in RBC

Answer 28

No carbonic anhydrase to convert carbonic acid into co2 and water

Question 29

What does CO bind to to stop o2 dissociation

Answer 29

Fe

Question 30

How does CO stop oxygen dissociation

Answer 30

Shifts it to the Relaxed state (high saturation)

Question 31

Why does co Hb have lower saturation

Answer 31

Rbc can’t pick up as much 02

Question 32

How can CO poisoning be treated

Answer 32

Oxygen hyperbaric therapy

Question 33

Why is NO binding to rbc important

Answer 33

Causes smooth muscle dilation to allow 02 dissociation to tissues

Question 34

How does NO bind

Answer 34

Bind to oxygenated

Or to Fe of deoxygenated rbc