Question

why proteins and lipids are not essentially taken as primary substrates in respiration ?

Answer 1

hey dear....... actually the lipids being highly greater in size can be mixed in blood causing chocked blood capillaries which results in disturbed blood supply to body tissues.....these lipid content is not efficient to our brain as u should know that the brain cells alone use up 20% of total glucose in the blood to perform respiration.... these lipid molecules can harm any cell causing enlarged cell size which is called TUMOUR......so lipids are mostly preferred only and only when there is a lack of glucose concentration in blood........

also proteins being the structures made up of a kind chain of amino acids when used in respiration , they undergo oxidation i.e. breakdown.......this releases the amino acids which then gets combined with hydrogen ions to form AMMONIA which is the most toxic chemical which can toxify our body tissues......so protein metabolism for respiration is also considered as supplimentary only when there is a lack of glucose and lipids i.e. fats in our body.....

hope u understood well.......

Answer 2

Answer:

Proteins and fats have to undergo a series of chemical reactions to form simple compound and then only they can enter Krebs Cycle( it is a cycle where our cells during aerobic respiration generate energy). ... Due to above reasons fats and proteins are not used as respiratory substrate and glucose is used.