L24. Gas Exchange, Transport and Cellular Respiration

Question 1

Partial pressure

Answer 1

Partial pressure= atmospheric pressure x composition percentage

Question 2

Alveolar air

Answer 2

• air in your lungs
  > humidified
  > exchanges gases with blood
  > mixed with residual air

Question 3

Gas exchange

Answer 3

• occurs between air in lungs and blood in capillaries through membranes
• gases diffuse down their concentration gradients

Henry’s law:
- amount of gas that dissolves in water is determined by its solubility in water and its partial pressure in air

Question 4

Basic steps in respiration

Answer 4

Respiration- the transport of O2 from the atmosphere into the body and CO2 from the body into the atmosphere

Four basic steps:

• pulmonary ventilation
• external respiration
• transport of respiratory gases
• internal respiration

Question 5

1. Pulmonary ventilation

Answer 5

• gas exchange between the atmosphere and air sacs (alveoli) in the lungs

Question 6

2. External respiration

Answer 6

• exchange of gases between alveoli and blood
• O2 moves from alveoli to blood
• CO2 moves from blood to alveoli

Question 7

3. Blood/ gas transport

Answer 7

• transport of O2 and CO2 between the lungs and the tissues

Question 8

4. Internal respiration

Answer 8

• exchange of gases between blood and tissues
• O2 moves from blood to tissues
• CO2 moves from tissues to blood

Question 9

Partial pressure in the alveolar air (oxygenated blood)

Answer 9

Pressure of O2= 100mmHg

Pressure of CO2= 40mmHg

Question 10

Partial pressure in tissues (deoxygenated blood)

Answer 10

Pressure of O2= 40mmHg

Pressure of CO2= 45mmHg

Question 11

Oxygen concentration in arterial blood

Answer 11

• more than 95% of the haemoglobin in your red blood cells should be bound to O2

Question 12

Oxygen binding to haemoglobin

Answer 12

• each haemoglobin is capable of binding to 4 O2 molecules
• oxyhaemoglobin (HbO2)
• deoxyhaemoglobin (HHb)

Question 13

Oxyhaemoglobin dissociation curve

Answer 13

• relationship between haemoglobin saturation and PO2 is not linear
• after binding with O2, haemoglobin changes shape to facilitate further uptake of more O2 (higher affinity to bind to O2) (positive feedback)

Question 14

Factors that influence Hb saturation

Answer 14

pH

• the lower the pH (increased acidity), the lower the oxygen binding affinity
• tissues have higher CO2, therefore higher acidity
• oxygen dissociates with HB when blood reaches tissues

TEMPERATURE

• the lower the temperature, the higher the oxygen binding affinity
• ie. oxygen binds to haemoglobin better in cold temperatures than warm temperatures
• oxygen dissociates with HB more readily at metabolizing tissues
  eg. during exercise (muscles are warm and acidic, so it promotes oxygen dissociation from Hb)

Question 15

** Oxygen dissociation curve shifts

Answer 15

Higher Hb-O2 Affinity (left shift)

• lower CO2
• higher pH
• lower temp

Reduced Hb-O2 Affinity (right shift)

• higher CO2
• lower pH
• higher temp

Question 16

carbon dioxide transport

Answer 16

• 90% of CO2 is transported in blood as carbonic acid (H2CO3)
• the rest travel as carbaminohaemoglobin (HbCO2) OR as dissolved gases

Question 17

What stimulates you to breathe

Answer 17

• respiratory rhythm is under neural control: medulla oblongata and pons

Rate and depth of breathing are adjusted to maintain levels of:

• pH
• partial pressure CO2
• partial pressure O2

Question 18

Effects of H+ ion- equation

Answer 18

CO2 + H2O –> H2CO3 –> HCO3- + H+

H2CO3 = carbonic acid 
HCO3- = bicarbonate 
H+ = hydrogen ion (higher the H+, lower the pH (acidic))

Question 19

Respiratory acidosis

Answer 19

• pH of blood < 7.35 (acidic)

Corrected by:

• hyperventilation (breathing faster with more depth)
• gets rid of CO2
• reduces H+
• increasing pH

Question 20

Respiratory alkalosis

Answer 20

• pH of blood > 7.45 (basic)

Corrected by:

• hypoventilation
• increases CO2
• increases H+
• lowers pH

Question 21

Hypoxia

Answer 21

• low oxygen levels