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Flashcards in Respiration Deck (12)
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Define respiration

the chemical reactions that break down nutrient molecules in living cells to release energy


Uses of energy in human body

muscle contraction, protein synthesis, cell
division, active transport, growth, the passage
of nerve impulses and the maintenance of a
constant body temperature


Define aerobic respiration

- the release of a relatively large amount of energy in cells by the breakdown of food substances in the presence of oxygen
- word equation: glucose + oxygen -> carbon dioxide + water
- symbol: C6H12O6 + 6O2 → 6CO2 + 6H2O


Define anaerobic respiration

- the release of a relatively small amount of energy by the breakdown of food substances in the absence of oxygen
- word equation (in muscles): glucose -> lactic acid
- word equation (in yeast): glucose -> alcohol + carbon dioxide
- symbol (muscles): C6H1206 -> 2C3H6O3
- symbol (yeast): C6H12O6 -> 2C2H5OH +2CO2


Describe the role of anaerobic respiration in yeast during brewing and bread-making

- Bread making:
+ yeast is mixed with water to activate it
then added to flour to make dough
+ mixture -----> warm place ------> rise
+ yeast releases CO2 ------> dough rises
+ when dough is cooked, high temp to kills yeast
and evaporates any formed ethanol
- Brewing:
+ yeast is added to a source of sugar (fruit juice or germinated barley grains) and kept in warm conditions
+ fermentation (yeast respires the sugar) occurs ------> ethanol is formed making the drink alcoholic
+ CO2 makes the drink fizzy + sharp flavour


Describe the effect of lactic acid in muscles during exercise

Muscles respire anaerobically when exercising vigorously, because the blood cannot supply enough oxygen to maintain aerobic respiration. Howerver, the
formation and build-up of lactic acid in muscles causes cramp, decreases pH


Adaptations of alveolis

Thin walls => shorter diffusion distance => increasing the rate
-Are balloon shaped => larger surface area for diffusion
-Walls of an alveolus are lined by thin film of water in which gases dissolve during diffusion => makes it faster


Describe the role of the ribs, the internal
and external intercostal muscles and the
diaphragm in producing volume and pressure
changes leading to the ventilation of the lung

When breathing in,
- The intercostal muscles relax
- The ribs raise upwards and outwards
- The diaphragm contracts and flattens
- The volume inside the thorax increases


State the differences in composition between
inspired and expired air

Gas Inspired Air Expired Air
Oxygen 21% 16%
Carbon Dioxide 0.04% 4%
Nitrogen 79% 79%
Water Vapour Variable High


Explain the role of mucus and cilia in
protecting the gas exchange system

Bacteria + dust particles are trapped by mucus, moved up to throat by cilia => as to not move further inside the gas exchange system.


Explain the link between physical activity and rate and depth of breathing

- Physical activity both increases rate and depth of breathing
- When exercise, the tissues respire more quickly and make more CO2 => lowers the pH in the tissues in the blood.
- Brain detects a rise in CO2 => sends nerve impulses to the diaphragm and intercostal muscles so they contract faster and further to increase rate and depth of breathing to lower the pH


Gas exchange

- Alveoli are tiny airs sacs in the lungs where gas exchange happens. Wrapping around alveoli are network of capillaries.
- Blood arriving in the alveoli : high co2 concentration (produced during cell respiration)
- Air in the alveoli: low co2 concentration
=> Co2 diffusing out of blood into the air of alveoli. Is then carried out by exhalation
- Blood arriving in the alveoli: low o2 concentration (b/c has been used by respiration)
Air in the alveoli: high o2 concentration
=> O2 diffusing out of alveoli, into the blood, combines with haemoglobin to transport oxygen