respiratory system

• Aerobic respiration - The process of food being broken down and the energy in it is released for use and temporarily stored in the form of a chemical called ATP (adenosine triphosphate)

  Glucose + oxygen -> Carbon dioxide + water + ENERGY

  • The food molecule respired is usually glucose
  • Oxygen is used up and carbon dioxide and water are produced as waste materials from the product
• Anaerobic respiration occurs if oxygen is in short supply such as during first 1-2 minutes of intense physical activity when more oxygen is needed than the body can supply.

  Glucose -> lactic acid + ENERGY

  • Muscle cells partially breakdown glucose and release some energy from it
  • less efficient than aerobic as glucose not fully broken down so less ATP is formed for each molecule of glucose used
• Anaerobic respiration causes lactic acid build up which causes the muscles to ache.

  1. Oxygen breaks down lactic acid and releases the remaining energy.
  2. When exercise finishes the body breathes faster and deeper to provide extra oxygen to break down the lactic acid.
  3. You are breathing in the oxygen that you needed during the exercise but could not get.
  4. An oxygen debt is built up which is the repaid after exercise.
• Germinating peas:

  1. seed begins to shoot and grow
  2. plant generates energy using aerobic respiration
  3. energy lost as heat
  4. disinfectant used to kill microbes as loss in heat may be because of them respiring not peas
  5. boiled peas act as control as enzymes denatured so cannot respire shows heat released is through respiration
• shows more carbon dioxide is present in exhaled air compared to inhaled air

  
• Gas exchange - the process by which oxygen and carbon dioxide move between the lungs and the blood

  ventilation - the movement of air in and out of the lungs
• Smoking:

  tar - clogs the bronchioles and coats the surface of the alveoli

  carcinogens - causes cancer

  nicotine - addictive, narrows blood vessels, increases heart rate

  carbon monoxide - reduced the amount of oxygen red blood cells carry around the body

  1. smoking paralyses the cilia
  2. clogs the mucus
  3. coughing damages the wall of the alveoli
  4. bronchial, diameter of airways reduced slower and harder gas exchange
• adaptions of alveoli:

  • large surface area (ensures maximum gas exchange)
  • rich blood supply (take absorbed oxygen away)
  • one cell thick (easier gas exchange)
  • surface is moist (dissolves oxygen so it can diffuse through membrane)
• adaptions of ciliated epithelial cells:

  • tiny hairs called cilia
  • produces sticky liquid mucus which traps microbes and dust
  • lots of mitochondria for energy
  • sweeps the mucus to keep lungs free from bacteria and airborne
• cotton wool - turns brown because of the tar

  lime water - turned cloudy because of CO2

  universal indicator - turns yellow because CO2 makes it acidic

  
• respiratory diseases:

  • chronic bronchitis - inflamed airways, overproduction of mucus blocks bronchi, breathing difficulties, decreases efficiency of gas exchange
  • emphysema - wall of alveoli stretched and loose elasticity, create build up of carbon dioxide in lungs, breathlessness, decrease in brain and heart efficiency
  • lung cancer - lung cells divide uncontrollably, thickened tissues gas cannot pass, may block airways, likely fatal unless treated early
• structure of the respiratory system

  
• bell jar model:

  • glass tube/trachea - splits into two, allows air to pass through, however glass is rigid and inflexible unlike cartilage bound trachea
  • bell jar/chest cavity - air tight, but unable to move, the ribs can move up and out to increase volume in thorax
  • balloons/lungs - can inflate and deflate, elastic like alveoli, but balloons are large open spaces whereas alveoli millions of individual
  • rubber sheet/diaphragm - domed up to increase jar volume, however diaphragm only flattens, is not pulled down like rubber sheet

  
• percentage of gas in inhaled air:

  • oxygen -> 21
  • carbon dioxide -> 0.04
  • Nitrogen -> 78

  percentage of gas in exhaled air:

  • oxygen -> 16
  • carbon dioxide -> 4
  • nitrogen -> 78

  we only use 5% of the oxygen we breathe in
• Inspiration (breathing in):

  • intercostal muscles contract, pulls ribcage up and out
  • diaphragm contracts, pulling downwards (flat)
  • volume of thorax increases, the pressure decreases
  • air is drawn into lungs down a pressure gradient
  • pressure in lungs lower than outside air so air is sucked in through the trachea

  
• Expiration (breathing out):

  • intercostal muscles relax, pulls ribcage down and in
  • diaphragm relaxes, doming upwards
  • volume of thorax decreases and pressure inside increases
  • air pushed out of lungs
  • pressure in lungs higher than pressure outside so air moves out through trachea

  
• the need for respiratory system:

  • very small animals exchange gases by diffusion across body surface
  • large animals need a respiratory system
  • they have a smaller surface area: volume ratio
  • SA insufficient to supply volume with oxygen
  • diffusion slow innermost cells in a large animals would die from oxygen deprivation before surface oxygen could reach them
  • large animals more active than small ones so more oxygen needed for extra energy