breathing

• Single celled organisms


  • They have large surface area compared to volume of cell (ratio)
  • It is easier to remove gases from inside to outside
• When comparison from surface area to volume is smaller (ratio)


  It is harder to get gases outside
• Mechanism


  Needed when surface area to volume ratio is smaller
• Mechanisms to increase surface area

  • Aligning them all
  • Being thin to create a short division way
  • Having a blood system to move the waste away
  • Ventilation system - forces gases out of body
• Adaptations for humans


  • Ratio of surface area to volume is so low, we need systems e.g. breathing system
  • Alveoli is to increase the surface area to enable effective diffusion of oxygen and carbon dioxide
• How breathing works


  1. Breath in: Intercostal muscles contract, ribs pulled upwards + outwards, diaphragm muscles contract, flattens diaphragm

  2. These movements increase volume of thorax, pressure decreases, air moves into lungs

  3. Breath out: Intercostal muscles relax, ribs drop down + in, diaphragm muscles relax, curved again

  4. Thorax gets smaller, pressure inside chest increases, air is squeezed and forced out of lungs
• Lungs


  • Protected by ribcage
  • Separated from abdomen by diaphragm
• Negative pressure ventilators


  1. Air drawn into lungs, exhaled passively as chest collapses

  2. Tight seal around neck, vacuum formed to lower pressure inside chest, air drawn in

  3. Vacuum switched off, pressure increases, air forced out of lungs
• Positive pressure ventilators


  1. Forces a carefully measured breath, like blowing up a balloon

  2. Once lungs inflate, air pressure stops, lungs then deflate forcing air out
• Aerobic respiration


  • Normal breathing, normal access to oxygen
  • Glucose + oxygen -> carbon dioxide + water
  • Mostly happens in mitochondria of cells
  • Number of mitochondria shows how active cell is
  • Energy is created through aerobic respiration, used for everything
• During exercise


  • Heart rate increases, arteries dilate to increase blood flow
  • Breathing increases, more oxygen brought in and carbon dioxide expelled
• Anaerobic respiration


  • Without oxygen (e.g. sprints)
  • Produces lactic acid
  • Glucose -> lactic acid
  • Blood flow removes lactic acid
  • Glucose not fully broken down
• After exercise


  Need to get rid of lactic acid, so breathe heavily to bring in oxygen to break it down
• Oxygen debt (panting after workout)


  Lactic acid + oxygen -> carbon dioxide + water
• Plants form ethanol + carbon dioxide during anaerobic respiration