1. Respiration Content Human Gaseous Exchange Aerobic Respiration Anaerobic Respiration Learning Outcomes: Candidates should be able to: (a) identify on diagrams and name the larynx, trachea, bronchi, bronchioles, alveoli and associated capillaries and state their functions in human gaseous exchange. (b) state the characteristics of, and describe the role of, the exchange surface of the alveoli in gaseous exchange. (c) describe the effect of tobacco smoke and its major toxic components – nicotine, tar and carbon monoxide, on health. (d) define and state the equation, in words only, for aerobic respiration in humans. (e) define and state the equation, in words only, for anaerobic respiration in humans. (f) describe the effect of lactic acid in muscles during exercise.

2. Atmosphere external nostril nasal passages pharynx larynx trachea bronchi bronchioles Alveoli external nostril trachea (wind pipe) larynx (voice box) pharynx bronchi bronchioles cluster of air sacs (alveoli) nasal passages 2 Respiration

4. PartsFunctions LarynxContain vocal cords to produce sound TracheaAllows air to enter and leave from the bronchi. - Supported by cartilage rings to hold it upright and ensure open airway - Epithelium secretes mucus to trap dust particles - Cilia lining helps to sweep the trapped dust particles up into the pharynx to be swallowed or expelled. BronchiTrachea divides into two bronchi for gaseous exchange BronchiolesEach bronchiole ends in a cluster of air sacs called alveoli AlveoliWhere gaseous exchange takes place as it is enclosed by a network of capillaries

6. Respiration Gaseous exchange in alveoli is due to concentration gradient Alveolar air has a higher concentration of oxygen but a lower concentration of carbon dioxide than blood capillaries entering the lungs Gaseous exchange takes place by diffusion in the lungs Alveolar wall (one cell thick/ single layer of cells) Thin film of moisture Blood capillary O2O2 CO 2 Blood with low concentration of oxygen Blood with high concentration of oxygen Alveolus

7. Respiration Adaptations of alveoli Structure/ structureFunction  Sac-shape and large number of alveoli  Provide a large surface area to increase rate of diffusion  Only one-cell thick (single layer of cell)  To increase the rate of diffusion of gases through it  Surfaces are covered with a thin film of moisture  Allows oxygen and carbon dioxide to dissolve in it, hence faster rate of diffusion  Enclosed by a network of capillaries  To maintain the diffusion gradient

8. Effects of Tobacco Smoke and its Components ComponentsProperties of the chemicalsEffects on the body 1) NicotineAddictive drug- Causes addiction to smoking Stimulate the release of adrenaline- Causes increased heartbeat and blood pressure Promotes blood clotting- Increase risk of coronary heart disease - Blood clot may lead to stroke or heart attack. 2) Carbon monoxide Bind to haemoglobin in red blood cell- Reduces transport of oxygen around the body. - Causes difficulty in breathing and may lead to death Increases the rate of fatty deposits on the inner arterial wall - Increase risk of atherosclerosis - Increase risk of coronary heart disease and heart attack 3) TarContains carcinogenic chemicals- Causes cells to divide abnormally and leads to lung cancer Paralyses cilia lining the air passages- Dust particles trapped in the mucus lining the airways cannot be removed, causing violent coughing - Increase risk of bronchitis (inflammation of bronchi) and emphysema (damaged alveoli walls, hence reduce uptake of oxygen) Accumulates on the surface of alveoli-Blockage in the air sacs. Hence reduces rate of diffusion of oxygen into alveoli

9. Respiration Aerobic respiration Glucose + oxygen  Carbon dioxide + water + large amount of energy Anaerobic respiration (Muscle cells) Glucose  lactic acid + small amount of energy Anaerobic respiration (yeast cells) Glucose  Carbon dioxide + ethanol + small amount of energy

10. Rate of respiration Breathing rate/ pulse rate increases during exercise because muscle tissues require more energy and rate of respiration increases. Hence, the heart beats faster to increase the rate of transport of oxygen to muscle tissues and increase rate of transport of waste products away from muscle tissues.

11. Respiration Effects of lactic acid in muscles during exercise: Lactic acid is toxic Accumulation of lactic acid causes muscle fatigue, pain or cramps Leads to oxygen debt (oxygen debt = extra oxygen needed to remove the lactic acid produced). Hence, breathing rate remains fast after exercise, e.g panting After exercise, lactic acid is transported to the liver, where it is either oxidized directly to produce energy, or converted back into glucose for use in muscles.

12. Respiration AEROBIC RESPIRATIONANAEROBIC RESPIRATION Presence of oxygenAbsence of oxygen Large amount of energy is released Little amount of energy is released Water and carbon dioxide are by- products Ethanol and carbon dioxide are by-products (yeast) Lactic acid and carbon dioxide are by-products (muscle cells)