gas exchange and transport

Question 1

Once air enters lungs how does O2 enter bloodstream & CO2 leave?

Answer 1

Gas exchange at the respiratory membrane

Question 2

describe the respiratory membrane layers

Answer 2

= 6 thin layers between alveolus & capillary

Question 3

name the 6 diff layers of the respiratory membrane

Answer 3

1. fluid and surfactant layer
2. alveolar epithelium
3. epithelial basement membrane
4. interstitial space
5. capillary basement membrane
6. capillary endothelium

Question 4

Respiratory Membrane is efficient because of:

Answer 4

1. Substantial differences in partial pressures across respiratory membrane
   - which leads to fast rate of gas diffusion
2. . Small distances involved in gas exchange
3. Gases are lipid soluble
4. Total surface area large

Question 5

what is Partial pressure (Px)

Answer 5

pressure exerted by each gasx type in a mixture

Question 6

explain daltons law

Answer 6

Px = % gasx times total pressure

So, gas moves from high Px to low Px

Question 7

explain the movement of gasses due to Px

Answer 7

Usually PO2 alveolar > blood

Whereas PCO2 blood > alveolar

this indicates that gas is moving from one tissue to another.

Question 8

Why feel lightheaded at high altitude?

Answer 8

Less O2 in alveoli, so ….

Slower diffusion into blood.

Question 9

explain the effect of high altitude (in terms of a water bottle filled w air)

Answer 9

LHS bottle filled at high altitude (so low pressure of air inside bottle)

Taken to sea level, bottle flattens as higher pressure outside bottle than inside (RHS).

Question 10

explain the process of internal and external respiration

Answer 10

external = pulmonary gas exchange

internal = systemic gas exchange

external:
on inhale oxygen is taken into alveoli then along pulmonary capillaries to left atrium. then….

internal:
….. oxygen goes along systemic capillaries to systemic tissue cells. carbon dioxide then exits the systemic tissue cells and transports along systemic capillaries to the right atrium and then to the lung and out via the alveoli into the atmosphere

Question 11

explain how Respiratory Membrane is efficient because of: Small distances involved in gas exchange

Answer 11

Thickness of Respiratory Membrane?
= 0.5mm

Decreased efficiency
if fluid builds up, as in
tuberculosis or
pneumonia

(RBC diameter = 6-8um)

Question 12

explain how Respiratory Membrane is efficient because of: Gases being lipid soluble

Answer 12

O2 & CO2 readily diffuse through surfactant layer & alveolar & endothelial cell membrane

Question 13

explain how Respiratory Membrane is efficient because of: Total surface area being large

Answer 13

Respiratory membrane s.a. ~70m2

= half singles tennis court.

Question 14

How are O2 & CO2 transported in the blood?

Answer 14

O2 & CO2 have limited solubilities in blood plasma

Problem solved by red blood cells (RBC) as :
- bind O2
- use CO2 to manufacture soluble compounds
(these are both temporary effects and completely reversible)

Question 15

explain the gas diffusion into blood (such as why it happens)

Answer 15

Because these reactions in RBC remove dissolved gas from the plasma, gas will continue to diffuse into blood but never reach equilbrium

Question 16

explain oxygen transport

Answer 16

O2 bound to iron ions in centre of each haem unit in a Hb molecule

4 haem units per Hb so 4x O2 per Hb molecule
~280 million Hb in each RBC

Each RBC potentially carry >billion O2 molecules

Question 17

in tissue spaces, oxygen diffuses what direction from Hb and what happens to it

Answer 17

away from Hb and enters tissues

Question 18

name 4 factors that influence the degree to which oxygen binds to Hb

Answer 18

P02
- oxygen-haemoglobin dissociation/saturation curve describes %Hb saturated at any PO2

blood PH
- Bohr effect

temperature

ongoing metabolic activity within RBC

Question 19

explain how Po2 influence the degree to which O2 binds to Hb

Answer 19

Curve (cf. straight line) as once bound, easier to bind 2nd molecule

• Easier to bind 2nd molecule of O2 due to shape change after 1st O2 bound. If CO is just 0.1% of air, enough Hb affected to die if not receive medical assistance; treat with pure O2 or transfuse with compatible RBC.

Carbon monoxide poisoning occurs as CO binds to Hb 200x stronger than O2

Lethal % CO level in air = 0.1%

Question 20

explain the O2-Haemoglobin Dissociation curve

Answer 20

If curve shifts to right, O2 released to tissues

Question 21

in the dissociation curve O2 released to tissues with…

Answer 21

Increasing temperature

Decreasing pH (more acidic)

Question 22

when do tight binding structure occur and what do they do

Answer 22

DPG = (di/biphosphoglycerate)

When 2,3-DPG binds to the Hb, the O2 is released

Question 23

what does a left shift curve mean and why

Answer 23

increased uptake of O2 in lungs

As Hb has increased ability to pick up O2

Question 24

explain Blood pH, Bohr effect
factors at influencing the degree to which oxygen binds to Hb

Answer 24

H+ binds to protein part of Hb

which affects shape of Hb

which affects amount of O2 carried

(Active tissue generates acid therefore decrease in pH therefore O2 released to tissues, where needed. Bohr effect (named after Danish physiologist Christian Bohr), is that Hb 2 binding affinity inversely proportional to acidity & CO2 concentration)

Question 25

explain how temperature influences the degree to which oxygen binds to Hb

Answer 25

As temperature rises, Hb releases more O2

So, as active muscles generate heat, the warmed blood releases more O2

To be used by the active muscle cells

Question 26

explain how ongoing metabolic activity within RBC influences the degree to which oxygen binds to Hb

Answer 26

2,3-biphosphoglycerate (BPG) produced during glycolysis (breakdown of glucose to produce ATP) increases release of O2

Question 27

name some Physiological adaptations to high altitude:

Answer 27

Increased respiratory rate

Increased heart rate

Elevated haematocrit
- % blood volume occupied by RBC

Can use centrifuge tubes to collect blood, or microcapillary tubes; both are spun in a centrifuge (adapted if using capillary tubes) where RBC sediment to base of tube.

Question 28

explain Haematocrit performed in microcapillary tubes

Answer 28

Can use centrifuge tubes to collect blood, or microcapillary tubes; both are spun in a centrifuge (adapted if using capillary tubes) where RBC sediment to base of tube.

Question 29

name the 3 main forms for co2 transport

Answer 29

Dissolved CO2 in plasma

Bound to protein portion of Hb (carbamino compounds)

Bicarbonate ions (HCO3-) [most H+ bind to Hb, acting as buffers, before affect plasma pH]

Question 30

explain CO2 transport in blood

Answer 30

Dissolved CO2 in plasma

Carbamino compounds (bound to protein of Hb)

Bicarbonate ions (HCO3-) in plasma (after CO2 + H2O with carbonic anhydrase forms carbonic acid [H2CO3], dissociating to HCO3-, leaving RBC as Cl- enters.

Question 31

explain the % of oxygen and CO2 thats physically dissolved in blood

Answer 31

1.5% oxygen
10% co2

Question 32

explain the % of oxygen and CO2 thats bound to Hb in blood

Answer 32

98.5% oxygen
30% co2

Question 33

explain the % of oxygen and CO2 thats bound by carbonate (HC03) in blood

Answer 33

none oxygen
60% CO2

Question 34

whats the main form of transport for oxygen

Answer 34

bound to Hb in blood

Question 35

whats the main form of transport for co2

Answer 35

as bicarbonate (HCO3)