(CIE A2 Biology) Respiration - respiratory substrates + quotients

respiratory substrates

molecules that can release energy to produce ATP in living cells

glucose molecules as respiratory substrates

can be obtained either from hydrolyzing disaccharides and polysaccharides or converting other monosaccharides using isomerases

lipid molecules as respiratory substrates

especially important in muscle tissue during prolonged periods of exercise as their higher C-H bond proportions mean they can release more H to reduce NAD+ and thus bulk-produce more ATP than with glucose (would require oxygen for complete metabolism though)

protein molecules as respiratory substrates

directly feed into the link reaction and Krebs cycle w/ the excess amino acids in them deaminated in the liver

ketoacidosis

occurs in prolonged fasting states as fatty acids get metabolized for acetyl-coA production - more life-threatening than the ketosis that precedes it as the acetyl-coA produced can then be converted into ketone bodies in the liver

the typical respiratory quotient for carbohydrates

1.0

the typical respiratory quotient for proteins

0.8

the typical respiratory quotient for lipids

0.7

the type of respiration occurring if the respiratory quotient exceeds 1.0

anaerobic respiration

respiratory substrate types ordered by their mean energy values

1. lipids (39.4)

2. proteins (17.0)

3. carbohydrates (15.8)