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Transport of Gases in Blood Notes

Transport of Gases in Blood

Overview of Blood Functions

  • Blood is a connective tissue that connects tissues and organs.

  • Functions include:

    • Transport of oxygen and nutrients to cells.

    • Transport of carbon dioxide and wastes away from cells.

    • Transport of hormones (chemical messengers) to cells.

    • Maintenance of pH in body fluids.

    • Distribution of heat and maintenance of body temperature.

    • Regulation of water content and ion concentration in fluids.

    • Protection against pathogens.

    • Clotting to prevent blood loss.

Transport of Oxygen in Blood

  • Oxygen is transported via:

    • Bound to hemoglobin in red blood cells (RBCs) - 97% of O2.

    • Dissolved in blood plasma - 3% of O2.

Red Blood Cells (RBCs) and Their Features

  • Structure: Biconcave discs, lack of nucleus.

  • Function: Transport oxygen from lungs to cells.

  • Hemoglobin:

    • Composed of four polypeptide chains that are bound iron-containing heme groups.

    • Each hemoglobin can bind four oxygen molecules, enhancing oxygen-carrying capacity by 60-70 times.

    • Because iron atoms bind oxygen, each haemoglobin molecule can combine with four oxygen molecules.

  • Shape Advantage: Biconcave shape increases surface area for diffusion and flexibility to traverse narrow vessels.

Reaction of Oxygen with Hemoglobin

  • Word Equation:

    • Oxygen + Hemoglobin ⇌ Oxyhemoglobin.

  • Reversibility:

    • The reaction between oxygen and hemoglobin is reversible at tissue beds allowing oxygen release where needed.

Transport of Carbon Dioxide in Blood

  • Carbon dioxide is a waste product from cellular respiration.

  • It is transported in the following ways:

    • 8% dissolved in blood plasma.

    • 22% combined with hemoglobin as carbaminohemoglobin.

    • 70% converted into bicarbonate ions through the following process:

    • Carbon dioxide + Water ⇌ Carbonic Acid (via carbonic anhydrase) ⇌ Bicarbonate Ion + Hydrogen Ion.

  • Reversibility of Carbon Dioxide Reaction: This reaction is also reversible; this allows for efficient gas exchange in the lungs.

Key Characteristics of Bicarbonate Formation

  • Faster in RBCs due to the presence of the enzyme carbonic anhydrase.

  • Bicarbonate ions readily diffuse into plasma once formed.

Definitions of Blood Types

  • Oxygenated Blood: High proportion of oxyhemoglobin; bright red in color.

  • Deoxygenated Blood: Low proportion of oxyhemoglobin; dark red/purplish in color.

Gas Exchange Process

  • Oxygen:

    • Diffuses from alveoli (higher concentration) to blood (lower concentration).

    • Leaves blood at tissues (higher concentration) to entering cells (lower concentration).

  • Carbon Dioxide:

    • Diffuses from tissues (higher concentration) to blood (lower concentration).

    • Exits blood into alveoli (higher concentration) from tissues during respiration.

Summary of Transport Mechanisms

  • In tissue beds:

    • Oxygen out of blood (into tissues) through diffusion.

    • Carbon dioxide into blood through diffusion.

  • In lungs:

    • Oxygen enters blood from alveoli.

    • Carbon dioxide exits blood to alveoli for respiration.