Respiratory substances
- Created by: portia
- Created on: 17-04-17 12:52
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Respiratory Substrates
- glucose is the essential respiratory substrate for some cells such as neurones, red blood cells and lymphocytes
- however other cells can oxidise lipids and amino acids
- when lipids are respired, carbon atoms are removed in pairs as, acetyl CoA, from fatty acid chains and fed into the Krebs cycle
- the carbon-hydrogen skeletons of amino acids are converted to pyruvate or acetyl CoA
Energy values of respiratory substrates
- most energy liberated in aerobic respiration comes from oxidation of hydrogen to water when reduced NAD and reduced FAD are passed to the ETC
- hence, the greater the number of hydrogens in the structure of a substrate molecule, the greater the energy value
- fatty acids have more hydrogens per molecule than carbohydrates so lipids have a greater energy value per unit mass or energy density, than carbohydrates or proteins
The energy value of a substrate is determined by burning a known mass of the substrate in oxygen in a calorimeter
- the energy liberated by oxidising the substrate is determined from the rise in temperature of a known mass of water in the calorimeter
Respiratory quotient (RQ)
- the overall aerobic respiration equation of glucose shows that the ratio of oxygen taken in and carbon dioxide released is 1:1
- when other substrates are respired the ratio of volumes of oxygen used and carbon dioxide released differ
- therefore measuring this ratio, RQ, shows which substrate is being used in respiration
- it can also show wheter or not anaerobic respiration is ocurring
- the RQ will be slightly less than…
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