Gas exchange

• What is gas exchange?


  The exchange of carbon dioxide and oxygen gases at cells and tissues through diffusion
• Where does gas exchange occur?


  In alveoli and respiring tissues
• What is ventilation?


  Movement of air in and out of alveoli
• What is the purpose of ventilation?


  To facilitate gas exchange
• What is respiration?


  Release of ATP from organic compounds
• What are the properties of gas exchange surfaces?


  • Large surface area
  • Very thin tissue layers
  • Permeable membranes
  • Concentration gradients
  • Covered in a layer of moisture
• How is the concentration gradient maintained for gas exchange?


  Through passive diffusion from high to low concentration
• What role does the dense capillary network play in gas exchange?


  It helps maintain concentration gradients
• How does continuous blood flow through capillaries aid gas exchange?


  It provides a continuous supply of blood with low oxygen and high carbon dioxide concentration
• What is the function of ventilation in the lungs?


  To bring in oxygen and remove carbon dioxide
• How do fish facilitate gas exchange?


  By moving water through their gills
• What are the adaptations of the lungs for gas exchange?


  • Branching bronchioles connect to many alveoli
  • Alveoli increase surface area
  • Type II pneumocytes secrete surfactant
  • Extensive capillary bed surrounds alveoli
  • Cartilage prevents collapsing
• What happens to thorax volume during inhalation?


  It increases, allowing air to enter
• What muscles contract during inhalation?

  External intercostal muscles
• What is the role of the diaphragm during inhalation?


  It contracts and moves down
• What occurs during exhalation?


  It is the opposite of inhalation
• What factors affect lung capacity?


  • Age (increases until 25)
  • Body size (larger size increases lung size)
  • Gender (males generally have larger lungs)
  • Respiratory diseases (e.g., asthma reduces lung capacity)
• What are the different lung volumes?

  1. Tidal volume
  2. Inspiratory reserve
  3. Expiratory reserve
  4. Vital capacity
  5. Residual volume
• What are the adaptations of leaf structure for gas exchange?


  • Waxy cuticle reduces evaporation
  • Epidermis protects mesophyll cells
  • Spongy mesophyll increases surface area
  • Air spaces facilitate gas diffusion
  • Stomata allow gas entry and exit
  • Veins provide structural support
• What is transpiration?


  Loss of water vapor through leaves
• What factors affect transpiration?


  Light intensity, temperature, humidity, and air flow
• What is hemoglobin when bound to oxygen called?


  Oxyhemoglobin complex
• What is deoxyhemoglobin?


  Hemoglobin when not bound to oxygen
• How many oxygen molecules can hemoglobin bind at full capacity?


  Four oxygen molecules
• What is fetal hemoglobin?


  Hemoglobin produced by the developing fetus during pregnancy
• What is the structure of fetal hemoglobin?


  It has two alpha and two gamma polypeptide chains
• Why does fetal hemoglobin have a higher affinity for oxygen?


  Due to the presence of gamma polypeptides
• What is the structure of adult hemoglobin?


  It has two alpha and two beta polypeptide chains
• What is the role of the prosthetic haem group in adult hemoglobin?


  Each chain has a haem group with an iron atom
• What is myoglobin?


  A transport molecule found in muscle tissue
• How many polypeptide chains does myoglobin have?


  One polypeptide chain
• What is the partial pressure of a gas?


  The pressure exerted by a single gas in a mixture of gases
• What does cooperative binding refer to in hemoglobin?


  The binding of one oxygen facilitates the binding of additional oxygen
• What does the oxygen dissociation curve represent?


  • Percent saturation of oxygen (y-axis)
  • Oxygen partial pressure in mmHg (x-axis)
  • Sigmoidal shape due to cooperative binding
  • Flattens at high partial pressure
  • Low affinity at low partial pressure
  • Conformational change increases oxygen affinity
• How does fetal hemoglobin's oxygen dissociation curve differ from adult hemoglobin's?


  Fetal hemoglobin's curve is to the left, indicating higher oxygen affinity
• Why is the oxygen dissociation curve important?


  It shows how oxygen is released in respiring tissues and taken up in the lungs
• How is carbon dioxide transported in the blood?


  1. Dissolved in blood plasma
  2. Bound to hemoglobin
  3. Converted to hydrogen carbonate ions and protons in red blood cells
• What is allosteric binding of carbon dioxide in hemoglobin?


  Carbon dioxide binds to an allosteric site, forming carbaminohemoglobin
• What effect does allosteric binding have on hemoglobin's oxygen affinity?


  It reduces oxygen affinity
• What is the Bohr shift?


  • Shift in the oxygen dissociation curve due to carbon dioxide partial pressure
  • Curve shifts to the right when carbon dioxide partial pressure increases