respiration in humans Flashcards
aerobic respiration
- > breakdown of glucose with the presence of oxygen with the release of large amount of energy
- > waste products are carbon dioxide and water
- > occurs in the mitochondria
• glucose[C6H12O6] + oxygen[O2] -> carbon dioxide[CO2] + water[H2O] + large amount of energy
anaerobic respiration
- > muscle cells can undergo anaerobic respiration for short durations when insufficient oxygen is available for aerobic respiration (e.g. during prolonged vigorous muscular contractions)
- > anaerobic respiration is the breakdown of glucose in the absence of oxygen
- > this process releases less energy compared to aerobic respiration
- > lactic acid is formed from the incomplete breakdown of glucose
- > occurs mainly in the cytoplasm
• glucose -> lactic acid + small amount of energy
during exercise
- muscles contracts and relax vigorously to enable more oxygen to reach the muscles
• by increasing the respiratory rate, the oxygen intake increases so that the increased oxygen demands of the body can be met. this can be done by:
-> increasing the frequency of breath
-> increasing the volume of air breathed in
• by increasing the heart rate, inhaled oxygen can be transported quickly to the relevant parts of the body - if the increased oxygen intake is not able to meet the oxygen demand, anaerobic respiration will take place to provide the energy required
- when anaerobic respiration occurs, lactic acid accumulates and the muscles incur an oxygen debt.
- an oxygen debt is the volume of oxygen required to remove lactic acid that has been built up
- accumulation of lactic acid in muscles may cause fatigue, muscle pains and cramps
after exercise
lactic acid is transported to the liver to be oxidised into energy. remaining lactic acid is converted back to glucose. oxygen debt is repaid.
cilia
epithelial cells have cilia that sweep trapped particles and bacteria up the bronchi and trachea, to the pharynx
mucus
gland cells secrete mucus that trap dust particles and bacteria in the air that is channeled to the lungs
structure of alveoli
millions of alveoli present
increase the surface area to volume ratio for rapid and efficient diffusion of oxygen molecules into blood capillaries
structure of alveoli
thin walls of alveoli and surrounding capillaries
thin walls which are only one-cell thick allows the gases to diffuse rapidly and easily across it
structure of alveoli
moist alveoli walls
allow oxygen molecules to dissolve (solution form) so that it can diffuse across the membranes
structure of alveoli
extensive network of blood capillaries on the walls of alveoli
constant flow of blood maintains the concentration gradient of gases to facilitate diffusion. this increases the rate of diffusion and transportation of gases at the alveoli.
removal of carbon dioxide
- tissue cells produce a large amount of CO2, as a result of aerobic respiration
- CO2 diffuses into the blood and enters the red blood cell
- CO2 reacts with H2O in red blood cells to form carbonic acid. this reaction is catalyse by carbonic anhydrase in red blood cells
- carbonic acid is converted into hydrogen carbonate ions and diffuses out of the red blood cells
- CO2 is carried as hydrogen carbonate ions in the plasma
- in blood capillaries at lungs, hydrogen carbonate ions diffuses back into red blood cell and converted back into carbonic acid, then into water and carbon dioxide by carbonic anhydrase.
- carbon dioxide diffuses out of the blood capillaries and enters the alveoli.
- it is removed from the lungs through exhalation
inhalation
- diaphragm contracts and flattens
- external intercostal muscles contract
- internal intercostal muscles relax
- ribs and sternum move upwards and outwards
- volume of thoracic cavity increases
- air pressure in lungs decreases
- atmospheric pressure is higher than air pressure in lungs
• air from atmosphere rushes into the lungs
exhalation
- diaphragm relaxes and recoils upwards
- external intercostal muscles relax
- internal intercostal muscles contract
- ribs and sternum move inwards and downwards
- volume of thoracic cavity decreases
- air pressure in lungs increases
- atmospheric pressure is lower than air pressure in lungs
• air forced out of the lungs into the atmosphere
effect of tabacco smoke
nicotine -> addictive -> promote blood clotting • person craves the next cigarette • increases the risk of thrombosis -- stroke -- heart attack
tar
-> contains carcinogenic (cancer-causing) chemicals
-> paralyses cilia lining in the air passages
• increases risk of lung cancer
• dust particles trapped in mucus lining the airways are not expelled effectively
• increases risk of chronic bronchitis and emphysema
– lung cancer
– chronic bronchitis
⚬ emphysema
carbon monoxide
-> combined readily with haemoglobin to form carboxyhaemoglobin
-> increases build-up of fatty deposits on inner arterial walls
• reduces ability of red blood cells to carry oxygen, hence reducing oxygen supply to cells
• increases risk of atherosclerosis
• increases risk of thrombosis
– coronary artery disease
irritant
-> paralyses the cilia lining the air passages
• increased risk of chronic bronchitis and emphysema
– chronic bronchitis
– emphysema
nasal cavity
atmospheric air is filtered, warmed and moistured as it enters the body through the nostrils and passes through the nasal passage (nasal cavity) into pharynx.
fringe of hair and the mucus layer on the walls of nasal cavity trap dust and foreign particles
