Bio 2601: Gas Exchange Lecture 6

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Questions and Answers

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

The limited surface area available for gas exchange in the respiratory system, affecting CO2 removal.

The rapid conversion of CO2 to carbonic acid in the lungs, hindering direct excretion.

The high concentration of CO2 in the air, creating a diffusion gradient that is unfavorable for excretion.

The low concentration of CO2 in the air necessitates a high partial pressure of CO2 for diffusion to occur. (correct)

In mammals, which of the following chemoreceptors plays the most significant role in regulating breathing, as indicated by the content?

Central chemoreceptors in the medulla. (correct)

Peripheral chemoreceptors in the carotid bodies.

Peripheral chemoreceptors in the aortic bodies.

Both peripheral and central chemoreceptors play equal roles in regulating overall breathing.

Considering the information provided, what is the main advantage water-breathers have over air-breathers in regard to CO2 excretion?

Water-breathers usually have low CO2 concentrations in water, which allows for easier diffusion out of their body. (correct)

Water-breathers have high concentrations of CO2 in their respiratory medium, causing a higher expulsion gradient.

The higher solubility of CO2 in water facilitates better excretion of the gas for water-breathers.

Water-breathers have a more developed respiratory system, allowing for efficient transfer.

For bimodal breathers, how is blood typically re-routed to manage oxygen and carbon dioxide exchange effectively?

Blood is re-routed such that oxygen is taken up mainly by the lungs from air while carbon dioxide is released mostly through the gills into the water. (A) Signup and view all the answers

Based on the provided content, what strategy do some air-breathing animals use when in water?

They absorb oxygen through the lungs in air and release carbon dioxide through their permeable skin in water. (C) Signup and view all the answers

In the context of oxygen transport, what is the role of respiratory pigments, and what unique adaptation is observed in the Antarctic icefish?

Respiratory pigments facilitate oxygen binding and transport; icefish lack them, utilizing increased blood volume to ensure sufficient oxygen supply. (B) Signup and view all the answers

According to the content, what is the primary mechanism by which most carbon dioxide is transported in the blood, and what role does carbonic anhydrase (CA) play in this process?

Most CO2 is transported as bicarbonate; CA facilitates its conversion to carbonic acid, in red blood cells from where it dissociates into bicarbonate and hydrogen ions (A) Signup and view all the answers

Based on the content, in what direction will the reaction $HbH + O_2 \rightleftharpoons HbO_2 + H^+$ in the tissues and the lungs?

The reaction favors $HbO_2$ formation in the lungs and $HbH$ formation in tissues due to the changes in partial pressure of oxygen. (A) Signup and view all the answers

During CO2 excretion at working tissues, how is the charge balance maintained when bicarbonate ($HCO_3^−$) is transported from red blood cells to the plasma, and what specific protein is responsible for this process?

Chloride ions ($Cl^−$) are transported into the RBCs through band 3 protein. (B) Signup and view all the answers

Following the description of $CO_2$ excretion, what happens to the majority of $HCO_3^−$ when it reaches the gas exchange surface (lungs/gills)?

It is converted back to $CO_2$ which then diffuses out into the lung/gill. (D) Signup and view all the answers

Study Notes

Lecture 6: Gas Exchange

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

Respiratory Pigments

Covered in Bio 2601
Students expected to know the topic
Students should understand hematocrit
Blood components diagram included

Antarctic Icefish

Lives in -1.9°C water
Lacks respiratory pigments
How does it get enough oxygen?
Possible advantages of lacking respiratory pigments?
Are there other animals without respiratory pigments?

Pigments & Oxygen Carrying Capacity

Graph showing oxygen equilibrium curve (total O2)
Relationship between partial pressure of O2 and oxygen content of blood
P50 values are shown on second graph
Describes high/low hemoglobin content

Percent Saturation of Oxygen

Graph shows percent saturation vs. partial pressure of O2
Formula shown is HpH + O2 ↔ HbO2 + H+

Oxygen Concentration of Blood

Graph showing O2 concentration vs. partial pressure of oxygen in blood
Illustrates changes in O2 concentration during rest and exercise

Effect of Temperature on P50

Graph showing how temperature affects oxygen saturation curves
Partial pressure of O2 in the blood is shown on graph

Hemoglobin at Working Tissues

Graph shows effect of pH change on hemoglobin saturation
Different pH levels (7.6, 7.4 and 7.2) are shown on the graph
Variation of CO₂ partial pressure are included on the graph

CO2 Excretion

Location of CO2 production
CO2 diffuses freely across epithelia/membranes
CO2 is not very soluble
Converting CO2 to bicarbonate (HCO3-)
Most CO2 transported as bicarbonate
Carbonic anhydrase role in RBCs
Diagram showing conversion reaction

CO2 Excretion: Working Tissues

CO2 diffuses from tissue to plasma & RBCs
Little CO2 binds to hemoglobin (Hb)
Converts to carbonic acid (H₂CO₃) by carbonic anhydrase (CA)
Then to bicarbonate (HCO₃⁻)
What happens to H⁺? effect on Hb?
Bicarbonate moves to plasma
Rapid anion exchange protein carries chloride ions (Cl⁻) into cells instead of bicarbonate
Explains CO2 transport in plasma as bicarbonate

CO2 Excretion: Gas Exchange Surface

Bicarbonate (HCO₃⁻) cannot diffuse across membranes
Converting back to CO2 for release
Effect on equilibrium

CO2 Excretion in Air-Breathers

Challenge of low CO2 levels in air
High pCO2 is needed for diffusion
Graph relating CO2 partial pressure to oxygen partial pressure

Blood Gases & Breathing

Chemoreceptors (peripheral, carotid, and aortic bodies and central medulla) involved in detecting blood gas levels
Details on chemoreceptor locations and roles

Regulating Breathing and Data Interpretations

Graphs relating ventilation rate (% values) to O2/CO2 % values in air/water breathers.
Data interpretations for air breathers

Unusual Air-Breathers

Issue of CO2 concentration for air breathers
Coping strategies used by different species

CO2 Excretion in Water-Breathers

CO2 excretion is generally easy in water due to water's solubility of CO2
conversion to bicarbonate
Diffusion gradient for CO2 and its consequences

What about Water Breathers?

Diagram showing oxygen partial pressure in relation to ventilation rate
Data for varieties of water vent rates

Gas Exchange: Bimodal Breathers

Oxygen exchange mainly via lungs
Carbon dioxide exchange mainly via gills
Blood routing required

Gas Exchange: Skin Breathers

Oxygen exchange through lungs and permeable skin
CO2 excretion data interpretation

Unusual Water Breathers

Nitrogenous waste excretion by freshwater fish
Conversion to ammoniac
Soda lakes/water high in CO2

Ornithine-Urea Cycle

Diagram of the cycle, and metabolic pathways involved

Studying That Suits You

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Description

Explore the concepts of gas exchange, focusing on topics such as CO2 exchange, respiratory pigments, and the unique adaptations of the Antarctic icefish. This quiz covers the physiological aspects of oxygen transport in the blood, including graphs that illustrate the oxygen equilibrium curve and percent saturation. Prepare to understand the mechanisms behind breathing regulation and blood oxygenation.