Summary Respiratory Substrates and Respirometers.

Respiratory Substrates & Respirometers:


 A respiratory substrate is an organic substance that can be used
for respiration.
 E.g.:
o Sugars + O2  CO2 + H2O
o Fats + O2  CO2 + LOTS OF H2O
o Proteins + O2  CO2 + H2O + Urea + Uric Acid + Salts.
 The majority of ATP is produced from oxidative
phosphorylation, so the more H atoms available in the
substrate, the more ATP that can be generated.


 Carbohydrates:
o Some polysaccharides (e.g. glycogen & starch) can be
broken down into glucose – glucose is the only possible
respiratory substrate for certain cells (e.g. brain & RBCs).
o Some monosaccharides (e.g. fructose & galactose) can be
converted to glucose in the liver.
o Other carbohydrates are also able to enter glycolysis.
 Lipids:
o When energy demands are great or carbohydrates are in
short supply, triglycerides are respired.
o Triglycerides are hydrolysed using the enzyme lipase,
breaking down to glycerol & 3 fatty acids.
o Glycerol is converted to pyruvate, which can then enter
glycolysis.
o Fatty acids are broken down in mitochondria to form
acetyl fragments that combine with coenzyme A to form
acetyl CoA, which enters the Krebs cycle.
o A large amount of reduced NAD & FAD is produced (from
all the H atoms on the fatty acid tails) which can then