Bio 2601: Gas Exchange and Pigments

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Questions and Answers

According to the provided information, what is the primary challenge for air breathers regarding CO2 excretion?

  • The high concentration of CO2 in the air makes diffusion difficult.
  • Air breathers must actively remove CO2 due to its insolubility.
  • The low concentration of CO2 in the air requires a high pCO2 for effective diffusion. (correct)
  • CO2 is converted to bicarbonate making it difficult to excrete.

According to the provided content, where are peripheral chemoreceptors located in mammals?

  • Skin
  • Lungs
  • Carotid and aortic bodies (correct)
  • Medulla

Based on the context provided, what is the main anatomical adaptation for gas exchange in bimodal breathers?

  • Re-routing of blood (correct)
  • Specialized structures in the medulla
  • Single circulatory system
  • Highly vascularized skin

Which of the following best describes the method of CO2 excretion for most water breathers?

<p>CO2 diffuses out into water, which has a lower CO2 concentration. (D)</p> Signup and view all the answers

According to the provided information, what is the primary means of O2 uptake for most bimodal breathers?

<p>Lungs (D)</p> Signup and view all the answers

According to the content provided, what chemical reaction is important in the context of CO2 in aquatic species?

<p>CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3- (D)</p> Signup and view all the answers

What is the primary function of carbonic anhydrase within red blood cells?

<p>To catalyze the interconversion of CO2 and H2O into H2CO3, which then dissociates into H+ and HCO3-. (A)</p> Signup and view all the answers

Based on the content, what mechanism does the equation $J = D \times A \times \frac{P1 - P2}{X}$ describe?

<p>Simple diffusion of gases (B)</p> Signup and view all the answers

How is the majority of CO2 transported in the blood?

<p>As bicarbonate (HCO3-) ions in the plasma. (D)</p> Signup and view all the answers

According to the provided information, freshwater fish mainly excrete which type of nitrogenous waste?

<p>Ammonia (B)</p> Signup and view all the answers

In working tissues, what is the immediate effect of increased CO2 concentration inside red blood cells?

<p>It reacts with water to form carbonic acid which then dissociates releasing H⁺ and this lowers pH within the cell. (A)</p> Signup and view all the answers

What role does the 'band 3' protein play in CO2 transport at the level of red blood cells?

<p>It exchanges Cl- for HCO3- across the red blood cell membrane, enabling the transport of bicarbonate. (C)</p> Signup and view all the answers

Where does the conversion of bicarbonate back to CO2 primarily occur, during gas exchange?

<p>At the respiratory gas exchange surface in the lungs or gills. (D)</p> Signup and view all the answers

What is the direct consequence of the conversion of H2CO3 to CO2 and H2O at the respiratory surface of the lungs/gills with respect to direction of CO2 movement?

<p>It allows for the conversion of HCO3- back to CO2, enabling CO2 excretion. (D)</p> Signup and view all the answers

In the context of the hemoglobin-oxygen binding curve, what does P50 represent?

<p>The partial pressure of oxygen at which half of the hemoglobin is saturated with Oxygen. (A)</p> Signup and view all the answers

Considering all the reactions shown in the material provided, which of the following would best explain the direction of the equilibrium?

<p>In the lungs/gills where O2 partial pressure is higher, the equilibriium of H2CO3 will shift towards CO2 and H2O. (A)</p> Signup and view all the answers

Flashcards

CO2 Diffusion

CO2 diffuses from areas of high partial pressure (PCO2) to areas of low partial pressure, facilitated by Fick's Law of Diffusion.

Partial Pressure of CO2 (PCO2)

The partial pressure of CO2 (PCO2) is the pressure exerted by CO2 gas in a mixture.

CO2 Excretion

The process of removing CO2 from the body, often through breathing in air-breathers.

Challenges for Air Breathers

Air breathers face challenges in excreting CO2 due to the low [CO2] already present in air.

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Advantages for Water Breathers

Water breathers benefit from the low [CO2] in water, making CO2 excretion easier.

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Gas Exchange

The process of exchanging gases between an organism and its environment, typically using organs like lungs or gills.

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Bimodal Breathers

Animals that can breathe both air and water, like lungfish and certain amphibians.

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Skin Breathing

The process of using the skin as a surface for gas exchange, in addition to lungs or gills.

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What are respiratory pigments?

Respiratory pigments are molecules that bind to oxygen and increase the oxygen carrying capacity of blood. Hemoglobin is the most common respiratory pigment in vertebrates.

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Why can Icefish survive without respiratory pigments?

Icefish lack respiratory pigments, which means they rely on the direct dissolved oxygen in their blood to transport oxygen to their tissues. This is possible due to their cold environment and high blood volume.

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What is the P50 value?

The P50 value represents the partial pressure of oxygen at which hemoglobin is 50% saturated. It indicates the affinity of hemoglobin for oxygen.

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What factors can affect the P50 value?

Factors that can affect the P50 value include temperature, pH, and the presence of 2,3-DPG. Higher temperature, lower pH, and higher 2,3-DPG levels decrease the affinity of hemoglobin for oxygen, leading to a higher P50 value.

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How does hemoglobin behave at working tissues?

At working tissues, the partial pressure of oxygen is typically lower than in the lungs. This leads to a lower saturation of hemoglobin with oxygen, favoring oxygen release to the tissues.

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How is CO2 transported in the blood?

Carbon dioxide (CO2) is produced in cells during cellular respiration and must be eliminated from the body. CO2 is transported in the blood primarily as bicarbonate (HCO3-), facilitated by carbonic anhydrase within red blood cells. The carbonic anhydrase enzyme catalyzes the reversible reaction between CO2 and water to form carbonic acid (H2CO3) which then dissociates into bicarbonate and hydrogen ions.

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Explain the process of CO2 excretion at working tissues.

As CO2 diffuses from tissues into red blood cells, it combines with water to form carbonic acid (H2CO3) which then dissociates to bicarbonate (HCO3-) and hydrogen ions (H+). This increased H+ concentration lowers the pH, leading to the Bohr effect, which causes hemoglobin to release more oxygen to the tissues. The HCO3- is then transported out of the red blood cells, in exchange for chloride (Cl-) ions by the band 3 protein, into the plasma.

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How does CO2 excretion occur at the gas exchange surface?

At the gas exchange surface, i.e., the lungs or gills, the process reverses. Bicarbonate (HCO3-) in the blood is converted back to CO2, which then diffuses out of the blood into the alveoli or gills. The release of CO2 shifts the equilibrium of the reaction towards the formation of carbonic acid (H2CO3) and ultimately the formation of CO2 and water. This process helps drive the overall diffusion of CO2 from the blood into the alveoli or gills.

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Study Notes

Lecture 6: Gas Exchange

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

Respiratory Pigments

  • Covered in Bio 2601
  • Students expected to know hematocrit
  • Whole blood consists of plasma (~55% of blood volume) and components separated by centrifugation
  • Components include white blood cells (<1% of blood volume) and red blood cells/erythrocytes (~45% of blood volume).

Antarctic Icefish

  • Lives at -1.9°C
  • Lacks respiratory pigments.
  • How does it obtain enough oxygen?
  • Possible advantages of not having pigments?
  • Other animals that do not require pigments?
  • Shows data on oxygen solubility with temperature

Pigments & O₂ Carrying Capacity

  • Graph showing the relationship between partial pressure of oxygen (PO₂) and the milliliters of oxygen per 100 mL of blood (volume %); also for total oxygen
  • Oxygen equilibrium curve (total O₂).
  • P₅₀ (pressure of oxygen at 50% saturation) relates to hemoglobin content
  • Higher hemoglobin content equates to a lower P₅₀ Note: Data for figures include partial pressure of O₂ units of measurement (mm Hg and/or kPa) and corresponding quantities of oxygen.

Percent Saturation and Partial Pressure of O₂

  • Graph showing the relationship between percentage saturation of hemoglobin, along with the partial pressure of O₂. This shows the percentage saturation of hemoglobin at different partial pressures
  • P₅₀ represents partial pressure of O₂ where hemoglobin is 50% saturated

Oxygen Concentration of Blood and Partial Pressure of O₂

  • Graph illustrating oxygen concentration in blood (mL O₂ / 100mL) in relation to the partial pressure of oxygen
  • Shows oxygen concentration in blood at rest and during exercise, correlating with the partial pressures, including lungs at rest and exercise

CO₂ Excretion

  • Location of CO₂ production
  • Free diffusion of CO₂ across epithelia/membranes
  • Limited solubility of CO₂ in the form it exists
  • CO₂ being interconvertible to HCO₃ (bicarbonate)
  • Carbonic anhydrase function within RBC
  • Primary transport of CO₂ as HCO₃⁻

CO₂ Excretion: Working Tissues

  • CO₂ diffuses from tissue to plasma and red blood cells
  • CO₂ conversion to H₂CO₃ via carbonic anhydrase
  • Conversion of H₂CO₃ to HCO₃⁻ and H⁺
  • Effect on hemoglobin (Hb), including the name of this effect
  • HCO₃⁻ transport in blood plasma
  • Role of band 3 in maintaining a concentration gradient for exchange of chloride (Cl⁻) for bicarbonate
  • Transport of CO₂ in plasma as HCO₃⁻

CO₂ Excretion: Gas Exchange Surface

  • HCO₃⁻ limitation in diffusion across membranes
  • Re-conversion of HCO₃⁻ to CO₂
  • Effect on equilibrium and process behind this conversion
  • Importance of diffusion for CO₂ removal

CO₂ Excretion: Air Breathers

  • Difficulty in excreting CO₂ with low CO₂  in air
  • Need for high pCO₂ for diffusion
  • Data interpreted: Relationships between CO₂ partial pressure and oxygen partial pressure

Blood Gases & Breathing

  • Chemoreceptors (peripheral and central) for regulating breathing
  • Peripheral chemoreceptors locations (carotid and aortic bodies)
  • Role of central chemoreceptors (medulla)
  • Most important factor in regulating breathing

What Regulates Breathing?

  • Interpretation of data related to air-breathers versus water-breathers for volume relations

Unusual Air-Breathers

  • Where CO2 might create challenges for air breathers
  • Methods employed to cope with high CO₂ concentrations

CO₂ Excretion: Water Breathers

  • Easy excretion of CO₂ in water due to low CO₂ concentrations
  • What happens to excreted CO₂
  • Consequences of CO₂ excretion
  • Chemical formula describing CO₂ reaction with water

What About Water Breathers?

  • Discussion on chemoreceptors involved in respiratory reflexes in neotropical fish
  • Data on results for animal testing, relating to P₅₀ values

Gas Exchange: Bimodal Breathers

  • Two respiratory systems, air and water, in some animals
  • Re-routing of blood for gas exchange

Gas Exchange: Skin Breathers

  • O₂ uptake through lungs and permeable skin in water-based animals
  • CO₂ excretion interpretative data; correlation between O₂ uptake and CO₂ excretion among different life stages in relation to respiration
  • Data relating to different developmental and environmental characteristics.

Unusual Water Breathers

  • Nitrogenous wastes in freshwater fish
  • NH₃ diffusion across gills and the forms of NH4+
  • "Soda Lake" environment and CO₂, bicarbonate, and pH correlations
  • Effects of high pH on CO₂ and NH₄⁺ diffusion
  • Other species, such as tilapia, are discussed

Ornithine-Urea Cycle

  • Biochemical pathway for urea synthesis
  • Diagram of biochemical reactions, including relevant enzymes such as glutaminase and glutamate, asparate and arginine.
  • Molecules involved in the cycle, including glutamine, glutamate, 2-oxoglutarate, carbamoyl phosphate, ornithine.

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Lecture 6 Notes on Gas Exchange - PDF

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