Amino acids as fuel molecules

Question 1

How are amino acids used as fuel?

Answer 1

Pool of free amino acids in a cell - used to make proteins, and other things
Chemical energy stored in bond so can use amino acids as a fuel molecule
To be able to use the energy from the amino group we need to do a deamination which removes the nitrogen

Question 2

What is deamination?

Answer 2

Nitrogen part is being cleaved and is released into solution, ketone group added on instead
This is done by a glutamate dehydrogenase enzyme
This can only happen in some amino acids

Question 3

What is transamination?

Answer 3

Transamination - amino group is taken off but added to something else rather than going into solution
To do transamination reactions we need a co-enzyme, PLP, which is derived from vitamin B6. This coenzyme carries the amino group from the amino acid to the keto acid

Question 4

First step of transamination

Answer 4

Amino group is taken off amino acid and transferred to the pyridoxal phosphate which becomes pyridoxamine phosphate (state where PLP is carrying amino group)

Question 5

Second step of transamination

Answer 5

Amino group taken off pyriodxamine phosphate and transferred to the keto acid. Keto acid becomes an amino acid, pyridoxamine phosphate becomes pyridoxal phosphate (state where PLP is not carrying an amino acid)

Question 6

Can keto acids be fed into metabolic pathways?

Answer 6

Some keto acids can directly feed in/enter the metabolic pathways, alanine into pyruvate, aspartame into oxaloacetate and glutamate into a-ketoglutarate. Some keto acids require modification first

Question 7

How do muscles use amino acids and how are they broken down?

Answer 7

Muscles use amino acids as a fuel molecule, once we have broken down carbons we are left with amino groups that can build up -> toxic to cells
To break down amino groups we take a keto acid and put the amino group on to turn it back into glutamate which uses another carbon skeleton

Question 8

How is nitrogen removed from the body?

Answer 8

To remove nitrogen from cells we use transamination reactions, glutamate is transferred into alanine via pyruvate enzyme and alanine is released into the blood. When the blood reaches the liver the alanine will be taken up and we can transamination the amino acid back to glutamate from alanine, nitrogen can be chopped off glutamate and will be taken out of the body via the urine