Gas Exchange and Oxygen Transport

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Questions and Answers

Which of the following factors directly increases the formation of 2,3-bisphosphoglycerate (BPG) in red blood cells?

Increased pH

Certain hormones, such as thyroxine, growth hormone, epinephrine, norepinephrine, and testosterone (correct)

Decreased temperature

Increased carbon dioxide levels

What is the primary means by which carbon dioxide is transported in the blood?

Directly attached to red blood cell membranes

Dissolved in blood plasma

Bound to hemoglobin as carbamino compounds

Converted to bicarbonate ions (HCO3-) (correct)

Which of the following conditions would likely result in a leftward shift of the oxygen-hemoglobin dissociation curve?

Increased temperature

Decreased pH (acidosis)

Decreased carbon dioxide levels (correct)

Increased 2,3-bisphosphoglycerate (BPG) levels

During hypothermia, which of the following is most likely to occur?

Increased oxygen binding to hemoglobin (A) Signup and view all the answers

What is the primary mechanism by which the Bohr effect influences oxygen-hemoglobin binding?

Changes in blood pH (B) Signup and view all the answers

Which of the following is a consequence of the rightward shift in the oxygen-hemoglobin dissociation curve?

Increased oxygen release to tissues (C) Signup and view all the answers

How does carbon dioxide contribute to the release of oxygen from hemoglobin?

Carbon dioxide combines with water to form carbonic acid, which lowers pH and promotes oxygen release (C) Signup and view all the answers

Which of the following conditions will not lead to a rightward shift in the oxygen-hemoglobin dissociation curve?

Decreased pH (acidosis) (B) Signup and view all the answers

What is the relationship between hemoglobin saturation and the partial pressure of oxygen (PO2)?

As PO2 increases, hemoglobin saturation increases. (A) Signup and view all the answers

What is the Bohr effect?

The decreased affinity of hemoglobin for oxygen when the pH of the blood decreases. (D) Signup and view all the answers

What is the primary factor that determines the amount of oxygen bound to hemoglobin?

The partial pressure of oxygen in the blood. (B) Signup and view all the answers

What is the significance of the 2,3-bisphosphoglycerate (2,3-BPG) molecule in oxygen transport?

It decreases the affinity of hemoglobin for oxygen and promotes oxygen unloading in the tissues. (C) Signup and view all the answers

Which of the following terms refers to the exchange of gases between the alveoli of the lungs and the blood in the pulmonary capillaries?

External respiration (C) Signup and view all the answers

How does the partial pressure of carbon dioxide (PCO2) affect the affinity of hemoglobin for oxygen?

High PCO2 decreases the affinity of hemoglobin for oxygen. (B) Signup and view all the answers

What percentage of the total oxygen transported in the blood is dissolved in plasma?

1.5% (A) Signup and view all the answers

Which of the following processes describes the exchange of gases between the blood in the systemic capillaries and the tissue cells?

Internal respiration (A) Signup and view all the answers

Study Notes

Gas Exchange and Transport

External and Internal Respiration:
- External respiration is pulmonary gas exchange. O2 diffuses from the alveoli to blood in the pulmonary capillaries, and CO2 diffuses in the opposite direction. This converts deoxygenated blood to oxygenated blood, returning to the left side of the heart.
- Internal respiration is systemic gas exchange, exchanging O2 and CO2 between systemic capillaries and tissue cells. Oxygenated blood becomes deoxygenated as O2 is released, and internal respiration occurs throughout the body.

Oxygen Transport

Oxygen's Solubility: Oxygen does not dissolve easily in water. Only 1.5% of inhaled oxygen is dissolved in blood plasma; the remaining 98.5% is bound to hemoglobin in red blood cells.
Hemoglobin and Oxygen Binding: Oxygen and hemoglobin bind in a reversible reaction to form oxyhemoglobin. This binding is easily reversible.

Relationship Between Hemoglobin and Oxygen Partial Pressure

PO2 and Saturation: PO2 (partial pressure of oxygen) is the most important factor determining how much O2 binds to hemoglobin. Fully saturated hemoglobin is converted from reduced hemoglobin (Hb) to oxyhemoglobin (Hb-O2). Partially saturated hemoglobin is a mixture of Hb and Hb-O2.
Oxygen-Hemoglobin Dissociation Curve: The curve illustrates the relationship between percent saturation of hemoglobin and PO2 at normal body temperature.

Other Factors Affecting Hemoglobin Affinity for Oxygen

Acidity (pH): Lower pH (increased acidity) decreases hemoglobin's affinity for O2, causing more O2 to be released. This is known as the Bohr effect. Higher pH (alkalosis) has the opposite effect.
Partial Pressure of Carbon Dioxide (PCO2): An increase in PCO2 also decreases hemoglobin's affinity for O2, facilitating oxygen unloading. Lower PCO2 leads to a leftward shift.
Temperature: Increased temperature decreases hemoglobin's affinity for O2, causing more O2 to be unloaded. Higher temperatures increase the release of oxygen.

2,3-Bisphosphoglycerate (BPG)

Effect on Oxygen Affinity: BPG is a substance in red blood cells that decreases hemoglobin's affinity for oxygen, promoting its unloading.
Formation in Red Blood Cells: BPG is produced during glycolysis in red blood cells. Certain hormones (like thyroxine) increase BPG levels.

Carbon Dioxide Transport

Dissolved CO2: A small amount (7%) of CO2 is dissolved in blood plasma, diffusing into alveolar air upon reaching the lungs for excretion.
Carbamino Compounds: About 23% of CO2 combines with amino acids and proteins in blood forming carbamino compounds.
Bicarbonate Ions: Approximately 70% of CO2 is transported as bicarbonate ions (HCO3⁻) in blood plasma. This is part of a process where CO2 reacts with water to produce carbonic acid, which dissociates into hydrogen ions and bicarbonate ions.

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Description

This quiz covers the principles of gas exchange and oxygen transport in the human body. Key topics include external and internal respiration, the solubility of oxygen, and the binding of oxygen to hemoglobin. Test your knowledge of how oxygen is transported and exchanged in the circulatory system.