module 5 - 18.6 respiratory substrates Flashcards
what are respiratory substrates?
molecules that can be used as an energy source to allow the production of ATP from ADP and Pi
what is the normal respiratory substrate?
glucose
what other respiratory substrates are there (not glucose)
- triglycerides
- proteins
what can the fatty acids in a triglyceride molecule lead to?
formation of 50 acetyl CoA molecules and form up to 500 ATP molecules
what happens to triglycerides?
- triglycerides are hydrolysed into glycerol and 3 fatty acids
- glycerol converted to pyruvate and enters respiration at link reaction
- fatty acids hydrolysed to form acetyl groups and enter respiration at krebs cycle
what happens to proteins?
- proteins are digested into individual amino acids by proteases
- an amino acid is deaminated, the amine group is converted to ammonia and then urea by ornithine cycle
- remaining molecule is converted to pyruvate, which enters respiration at link reaction
what are ketone bodies?
- molecules that contain a ketone group
- produced when fatty acids are broken down for respiration during a period of long calorific restriction (e.g. starvation)
- brain uses ketone bodies to synthesise fatty acids
what does the words ‘ketone’ mean?
breakdown bodies from proteins
what are RQ values?
- respiratory quotient values
- unitless value that is the ratio of volume of carbon dioxide produced to volume of oxygen consumed
- expressed as a single value
- indicate what is the respiratory substrate
what is the equation for RQ?
CO2 produced
_______________
O2 consumed
what is the RQ for a carbohydrate, protein, lipid or tryglyceride and anaerobic respiration?
- carbohydrate: RQ = 1.0
- protein: RQ = 0.9
- lipid or triglyceride: RQ = 0.7
- anaerobic respiration: RQ = above 1.0
why is the RQ value of glucose 1.0?
because the volume of oxygen required to metabolise glucose in aerobic respiration is equal to the volume of carbon dioxide released from the body
what is respiratory quotient measured with?
respirometer
why do lipids/trigylcerides have a smaller RQ value?
- they contain more carbon-hydrogen bonds than glucose so they can produce more reduced NAD and reduced FAD and more ATPs
- this means they need less oxygen than glucose so have smaller RQ
what does a normal human metabolism produce an RQ value of?
0.8-0.9 indicating a mixture of all respiratory substrates