Week Eight

Question 1

What percentage of oxygen can travel as dissolved gas in the blood plasma?

Answer 1

1-2%

Question 2

How many binding sites does a hemoglobin molecule have?

Answer 2

4

Question 3

How does hemoglobin bind and release oxygen?

Answer 3

Two separate reactions: loading and unloading
Hemoglobin + O2 ←→ oxyhemoglobin

Question 4

What factors affect the affinity of O2-Hb binding? What does this mean

Answer 4

Increased temperature, decreased pH or increased PCO2 in the blood all cause a right shift in the Oxy-HB dissociation curve
→ this means that O2 will more easily unload at tissues

Question 5

What happens to O2 unloading when tissues have a higher metabolic rate (e.g. during exercise)?

Answer 5

they produce more CO2 H+ and heat → this will trigger more O2 to be released

Question 6

What causes the S-shaped curve of an Oxygen-Hemoglobin dissociation curve?

Answer 6

The more O2 bound to 1 Hb molecule → the stronger the bond

→ once Hb loses its first O2, it changes shape and has a lower affinity for the remaining 3. The last O2 is the least tightly bound to Hb

Question 7

Describe the three methods of transport of Co2 from least to more common

Answer 7

1. dissolved in the blood plasma (7-10% of Co2) (since Co2 is more soluble in blood than O2, more can be dissolved in the plasma)
2. bound to hemoglobin: carbaminohemoglobin (20% of Co2)
3. As bicarbonate in the blood (70%)

Question 8

What are the steps Co2 transport in the blood as bicarbonate

Answer 8

1. CO2 diffuses from the cells into the erythrocytes
2. CO2 is converted to carbonic acid
3. Carbonic acid dissociated into bicarbonate and hydrogen
4. hydrogen binds to Hb (Hb acts as a buffer to resist pH change)
5. Bicarbonate enters the plasma
   - carbonic anhydrase is the enzyme that catalyzes this reaction and the reverse reaction

Question 9

How is Co2 released once it reaches the pulmonary capillaries

Answer 9

1. Bicarbonate renters the RBCs
2. Carbonic acid is reformed in the the RBCs
3. Carbonic acid breaks down into water and Co2
4. Co2 diffuses into the alveolus

Question 10

How is normal blood pH (7.34 - 7.45) maintained

Answer 10

By bicarbonate
excess H+: bicarbonate + hydrogen → carbonic acid
low H+: carbonic acid → bicarbonate + hydrogen

Question 11

How does hyperventilation impact blood pH

Answer 11

more Co2 expired = low blood PCO3 → increased pH (low H+) → respiratory alkalosis

Question 12

How does Hypoventilation affect Co2 in the blood?

Answer 12

less CO2 expired = high blood PCO2 → decreased pH → respiratory acidosis

Question 13

What is Eupnea

Answer 13

normal breathing

Question 14

Where are our respiratory centres located that maintain our basic rhythm from breathing?

Answer 14

in the medulla

Question 15

What is the role of the central and peripheral chemoreceptors in the respiratory system?

Answer 15

specialized cells that detect changes in PCO2, PO2 and H+ in the blood (and Cerebrospinal fluid) in order to control the rate and depth of ventilation

Question 16

Describe the Central chemoreceptors of ventilation

Answer 16

• found in the medulla
• detect changes in PCO2 and in H+ by monitoring levels in the cerebrospinal fluid
• signal sent to regulate rate and depth of breathing in order to return levels to normal

Question 17

Describe the peripheral chemoreceptors of ventilation

Answer 17

• located in the aorta and carotid arteries
• detect changes in PCo2, H+ and PO2
• signals sent to medulla to increase rate and depth of ventilation

Question 18

Describe the negative feedback loop when PCo2 and/or H+ increase above their normal range

Answer 18

→ central chemoreceptors detect increases in PCo2 and/or H+ → chemoreceptors relay stimuli to the respiratory pattern generator → RPG triggers hyperventilation, and additional CO2 is lost