Bio 2601: Gas Exchange and Respiratory Pigments

Lecture 6: Gas Exchange

• Lecture date: January 17
• Topics covered: CO2 exchange, regulating breathing
• Readings: pages 677-685, 620-638
• Review pages: 654-677

Respiratory Pigments

• Covered in Bio 2601
• Students are expected to know the material
• Hematocrit is a topic to review

Antarctic Icefish

• Lives at -1.9°C
• Lacks respiratory pigments
• Has to get enough oxygen
• Possible advantages of not having pigments
• Other animals that lack respiratory pigments

Pigments & Oxygen Carrying Capacity

• Graph describing oxygen equilibrium curve
• Shows total oxygen
• Indicates dissolved oxygen
• Measures partial pressure of oxygen (02)
• Measurement of Oxygen content of blood (mmHg)
• Discusses high and low hemoglobin content

Percent Saturation of Oxygen

• Graph displaying percent saturation of oxygen
• Demonstrates the relationship between partial pressure of oxygen and percent saturation

Oxygen Concentration of Blood

• Graph depicting oxygen concentration in blood
• Illustrates the relationship between oxygen partial pressure and blood oxygen concentration at rest and during exercise
• Shows blood flow in lungs and systemic tissues

What can Change Oxygen Partial Pressure?

• Graph illustrating changes in oxygen partial pressure based on temperature.
• Shows percent saturation
• Illustrates partial pressure of oxygen in blood

Hemoglobin at Working Tissues

• Multiple graphs showing hemoglobin saturation at different pH levels and CO2 partial pressures
• Shows oxygen delivery in different conditions

CO₂ Excretion

• CO2 production location
• CO2 diffuses freely across epithelia and membranes.
• CO2 is not very soluble in its normal form
• Conversion to bicarbonate (HCO3-) is possible.
• Carbonic anhydrase helps with conversion
• Most CO2 is transported as HCO3-

CO₂ Excretion: Working Tissues

• CO2 diffuses from tissue to plasma and RBC.
• Very little CO2 binds to hemoglobin (Hb).
• Most CO2 is converted to H2CO3 by carbonic anhydrase (CA).
• The H+ ions produced by the reaction affect Hb.
• Bicarbonate is then transported in the plasma using band 3 and exchanging chloride in the process

CO₂ Excretion: Gas Exchange

• Bicarbonate (HCO3-) cannot cross cell membranes.
• CO2 is reconverted and diffuses out of the lungs.

CO₂ Excretion: Air Breathers

• Air breathers face a CO2 challenge due to low CO2 in air, needing higher pCO2 for diffusion.
• Diagrams show how partial pressure is related to oxygen partial pressure.

Blood Gases & Breathing

• Chemoreceptors (peripheral and central) in animals detect blood gases and regulate breathing
• Peripheral chemoreceptors: carotid and aortic bodies
• Central chemoreceptors: medulla

What Regulates Breathing?

• Diagrams show how air versus water-breathing organisms respond to changes in oxygen partial pressure (PO2) and carbon dioxide partial pressure (PCO2).
• Data indicate how breathing rates vary with these values.

Unusual Air-Breathers

• Focuses on how CO2 becomes a challenge for unusual air-breathers.
• Graphs display correlation between inspired CO2 and respiratory rate.

CO₂ Excretion: Water Breathers

• CO2 excretion in water breathers is typically much easier because water has relatively high CO2 solubility
• Explains what happens to excreted CO2, and the consequences of this process.

What About Water Breathers?

• Discussion of extra-branchial chemoreceptors and their role in respiratory reflexes in the neotropical fish.
• Some data displays shows ventilation rates versus oxygen partial pressure

Gas Exchange: Bimodal Breath

• O2: mostly lungs from air
• CO2: mostly gills to water
• Re-routing of blood is necessary

Gas Exchange: Skin Breathers

• O2: lungs in air, permeable skin in water
• CO2: interpret the data about skin-breathing organisms

Unusual Water Breathers

• Discusses nitrogenous waste excretion in freshwater fish.
• Explains why ammonia (NH3) is the usual waste product, and how it's treated by animals.
• Presents an example of a location (Lake Magadi, Kenya) with high CO2 partial pressures, and its affect on breathing, and NH3 excretion

Ornithine-Urea Cycle

• Diagram of the ornithine-urea cycle
• Shows the metabolic pathway for the synthesis and excretion of urea in ureotelic organisms.