Nitrogen metabolism Flashcards
is there a store of nitrogen in the body
- No significant store of nitrogen within the body, therefore the nitrogen has to be balanced in the body
when does positive nitrogen balance happen
If intake exceeds output
- Periods for growth
- Pregnancy -
- tissue repair
when does negative nitrogen balance happen
If output exceeds input
- indicates body protein breakdown
- Fasting
- Trauma
- Protein malnutrition
- serious tissue wintry
- fever
- wasting diseases
what are conditional essential amino acids
- Some capacity to make ourselves but if the demand is particularly high then we have to make them from the diet as well
what are amino acids used for
- Amino acids are essential and important
- Used to make body proteins
- Used to make purines, pyrimidines – nucleotides to make new DNA and RNA
- Used to make thyroxine
- Used as neurotransmitters – directed in the form of glutamate or indirectly to make noradrenaline
- Used to make coenzymes and melanin
- Amino acids are also used to make glucose and ketone bodies
what amino acids can be used to make what neurotransmitters
- Tyrosine – important in making melanin, dopamine, adrenaline, noradrenaline dn thyroxine, phenylalanine can compensate for low tyrosine
- Tyrptophan- serotonin and melatonin
- Arginine – nitric oxide
- Histidine – histamine
- Glycine, glutamate and aspartate – used directly as neurotransmitters
if you add an amine group on a Keto acid it..
becomes an amino acid
what amino acid does pyruvate become
- Pyruvate (keto acid)becomes alanine (amino acids)
what amino acid does alpha ketoglutarate become
- Alpha ketoglutarate (keto acid) becomes glutamate (amino acids)
what amino acid does oxaloacetate become
- Oxaloacetate (keto acid) add an amino group becomes aspartate (amino acids)
what vitamins is required for Keto acids to turn into amino acids
B6
what sub goroup of amino acids are there
glutagenic amino acids and ketogenic amino acids
what are glutagenic amino acids used for
can be used in glyconeogensis to make glucose
name some glutagenic amino acids .
- alanine
- aspartate
- glutamine
- glutamate
what can glutagenic amino acids be used to make
- Alanine can be used to make pyruvate
- Asparate can be used to make oxaloacetate
- glutamine and glutamate can be used to make alpha ketoglutarate
what are ketogenic amino acids
- these are amino acids that can be used to make ketone bodies
describe how ketone amino acids are made
- these ketone bodies are made from acetyl CoA, therefore if you can break the carbon skeleton of an amino acid down to acetyl – CoA then we can make ketone bodies
what are the soles ketogenic amino acids
leucine
lysine
what ketogenic amino acids can make acetoacetyl-CoA
- leucine
- lysine
- phenylalanine
- tyrosine
- tryptophan
what keotgneic amino acids can be used to make acetyl-CoA
- isoleucine
- leucine
- tryptophan
describe how phenylalanine can be converted to glucose
- Phenylalanine changed to tyrosine
- This is then broken down into p-hydroxyphenylpyruvate this is then converted to acetoacetate and fumarate which can be broken down to glucose
what can phenylalanine compensate for
- Phenylalaine can compensate for low levels of tyrosine
what are the branched chain amino acids
leucine isoleucine and valaine
how are branch amino acids broken down
- Firstly they loose there amino group
- Then they gain CoA
- Then there is a dehydrogenation reaction
- Valine is broken down to succinylCoA
- Isoleucine to proionylCoA and acetyl CoA
- And leucine to B-hydroxy-Bmethyl glutaryl CoA and then acetoacetate and acetyl-CoA
what is isoleucine broken down into
- Isoleucine to proionylCoA and acetyl CoA
what is leucine broken down into
leucine to B-hydroxy-Bmethyl glutaryl CoA and then acetoacetate and acetyl-CoA
what is valaine broken down into
- Valine is broken down to succinylCoA
why is ammonia converted to urea
- Ammonia is basic and highly reactive, it can form neurotransmitters
- Needs a large amount of water to excrete it
- Ammonia is converted into urea
- Urea is more water soluble and less toxic therefore it takes less water to excrete it
what are the 3 different fates of glutamate
- Glutamate can undergo a transamination reaction with pyruvate producing alanine and alpha ketoglutarate - alanine can go to the liver where it is converted back to pyruvate producing glutamate, pyruvate is also produced and turned to glucose
- Or glutamate can be deaminated directly producing alpha ketoglutarate and ammonia – the ammonia can go straight to the kidney where it is disposed of
- Or glutamate can be converted to glutamine by combining with one molecule of ammonia - this goes to the kidney where it is used for acid base balance
what happens to excess amino acids in skeletal muscles
- There is excess amino acids being converted into glutamate
what are the enzymes involved in glutamate metabolism
- Glutamate dehydrogenase
- Glutamate adding an amino group to make glutamine is added by glutamate synthase
- Glutmase converts glutamine to glutamate and produces ammonia as well
what is the role of glutamate
- Skeletal muscle – syntehsised, stored and released in fasting
- Kidney – substrate for gluconeogenesis; formation of ammonia for buffering protons
- Central nervous system; shuttle for the maintenance of glutamate as a neurotransmitter
- Immune cells; fuel and enhances T lymphocyte response to infection; also supports phagocytosis by neutrophils and macrophages
describe the urea cycle
- Once in the liver
- There is the amino acid glutamate this is converted into alpha ketoglutarate and free ammonia by GDH
- The ammonia is converted to carboamyoyl phosphate by CPS this uses 2 molecules of ATP in the process
- Carbonyl phosphate is converted to citrulline by combining with ornitihine
- Then combined with aspartate to make arginosuccinate,
- Converted to arginine
- Releases urea and converted back to ornithine
how is the urea cycle controlled
- This is through control of CPS
- It is sensitive to the levels of N-acetyl glutamate
- This is made by glutamate binding to acetyl-CoA
- This means that the urea cycle only occurs when the level of glutamate and acetyl-CoA are high
what is nitrogen balance
Nitrogen balanceis a measure ofnitrogeninput minus nitrogen output.
Nitrogen Balance = Nitrogen intake - Nitrogen loss
describe transamination
- chemical reaction between two molecules
- one is an amino acid which contains an amine group
- the other is a keto acid which contains a Keto (=0) group
- the amino group on one molecule is exchanged with the =O group on the other molecule, the amino acid becomes a Keto acid and the Keto acid becomes an amino acid
what is the glucose alanine cycle
- this is when the ammonium ion is transported from muscle cells to the liver in the from of alanine
- through glycolysis glucose becomes pyruvate in the muscle
- the particular ion of pyruvate in transmiantion reaction produces alanine
- alanine is then transported into the liver
- it is then transaminate again and produces pyruvate
- this can be used for gluconeogensis yielding
- glucose can be sent again to the muscle and produce energy
what does glutamate act as
- it acts as a collector of amino group of the amino acids
- all the amino nitrogen from amino acids that undergo transamination can be concentrated in glutamate
