Chapter 3: breathing

• What is the surface area to volume ratio in single-celled organisms?

  Relatively large
• Why can small organisms diffuse nutrients across their membrane?

  They have a large surface area to volume ratio
• What happens to the surface area to volume ratio as organisms grow larger?

  It gets smaller
• What is a consequence of a smaller surface area to volume ratio in larger organisms?

  Difficulty in exchanging materials quickly
• What cannot reach every cell in larger organisms by simple diffusion?

  Gases and food molecules
• What must be removed quickly to avoid poisoning cells?

  Metabolic waste
• What are the adaptations for exchanging materials in multicellular organisms?

  • Large surface area for exchange
  • Thin structure for short diffusion path
  • Efficient blood supply to maintain concentration gradient
  • Ventilation to enhance gas exchange
• What is gas exchange?

  Transfer of oxygen and carbon dioxide
• Where does gas exchange occur in the lungs?

  In the alveolus wall lining
• Where are the lungs located in the body?

  In the thorax
• What protects the lungs?

  The ribcage
• What is the primary function of the breathing system?

  To move air in and out of the lungs
• What happens during inhalation?

  The ribcage expands and diaphragm flattens
• What causes air to flow into the lungs during inhalation?

  Higher atmospheric pressure
• What occurs during exhalation?

  The ribcage relaxes and diaphragm curves upwards
• What causes air to flow out of the lungs during exhalation?

  Higher pressure in the lungs
• What are the adaptations of the lungs for gas exchange?

  • Large surface area for faster diffusion
  • Thin walls for short diffusion distances
  • Good ventilation to maintain diffusion gradients
  • Dense capillary network for high concentration gradients
• What do alveoli provide for gas exchange?

  A very large surface area
• What is the role of blood capillaries in the alveoli?

  To supply rich blood for gas exchange
• Why are the walls of alveoli thin?

  To provide a short diffusion distance
• Why are the walls of alveoli moist?

  To help gases dissolve and diffuse faster
• What is a ventilator?

  A machine that aids breathing
• How does a negative pressure ventilator work?

  Creates a vacuum to inflate lungs
• What happens when the negative pressure ventilator is switched off?

  Air is pumped back into the chamber
• What is the application of negative pressure ventilators?

  To support polio sufferers
• How does a positive pressure ventilator function?

  Forces air into the lungs under pressure
• What is a common application of positive pressure ventilators?

  Used during major surgery
• What is respiration?

  A chemical reaction producing energy
• Where does respiration occur in cells?

  In the mitochondria
• What is aerobic respiration?

  Breakdown of nutrients using oxygen
• What are the waste products of aerobic respiration?

  Carbon dioxide and water
• What is the word equation for aerobic respiration?

  Glucose + oxygen → carbon dioxide + water
• What is the symbol equation for aerobic respiration?

  C$_6$H$_{12}$O$_6$ + 6O$_2$ → 6CO$_2$ + 6H$_2$O (+ATP)
• Why do living cells need to respire?

  To carry out basic life functions
• What do muscles need energy for?

  To contract during movement
• How do mammals and birds maintain their body temperature?

  Through energy transfer from active muscles
• How do plants use respiration?

  For active transport and protein synthesis
• What is muscle tissue made of?

  Protein fibres
• What do muscle fibres contain to carry out aerobic respiration?

  Many mitochondria
• What do muscles store as a carbohydrate?

  Glycogen