GAS EXCHANGE

• Gases are important because they are required for different metabolic reactions to proceed.
• Gas exchange is also an important biological process that allows organisms to survive.
• Different structures used by animals for gas exchange

  • CELL MEMBRANE It is a structure used by unicellular organisms for gas exchange. Gases directly pass through the cell membrane through diffusion.
  • SKIN/ BODY SURFACE It is a respiratory surface covered with thin and moist epithelial cells that allow oxygen and carbon dioxide exchange. Gases can only cross the cell membrane when they are dissolved in an aqueous solution, and thus the surface should be moist. example: amphibians
• • GILLS They greatly increase the surface area for gas exchange in aquatic organisms. Gills are convoluted outgrowths containing blood vessels covered by a thin layer of epithelial cells. They can be found either externally or internally.
  • Inhaling - mouth open (water + oxygen), gills closed
  • Exhaling - mouth closed, gills open ( water + carbon dioxide)
• • LUNGS These are ingrowths of the body wall that connect to the outside environment by a series of respiratory tubes and small openings. The lungs are one of the most complex respiratory organs of animals.
  • It starts with the diffusion of oxygen from the respiratory surface into the blood, which will then transport the oxygen to the cells of the different parts of the body. As oxygen diffuses into the cells, carbon dioxide is absorbed into the bloodstream, which will subsequently be released to the environment through the respiratory surface.
• In plants, gas exchange mainly occurs in the leaves.
• In photosynthesis, plants take in carbon dioxide from the air to make food; during the process, oxygen is released as a byproduct.
• Roots and stems also contribute to gas exchange but only with a minimal effect.
• These (outer bark) cork cells are impregnated with suberin, a waxy, waterproof substance that does not allow gases and water to pass through.
• woody stems and mature roots are perforated by nonsuberized pores called lenticels.
• Lenticles provide a pathway for the direct exchange of gases between the internal tissue of the plant and the atmosphere.
• • TRACHEAL SYSTEMS They are composed of a series of respiratory tubes that carry the gases directly to the cells for gas exchange. Gases enter and exit through the openings at the body surface called spiracles.