Nitrogen metabolism Flashcards
1
Q
is there a store of nitrogen in the body
A
- No significant store of nitrogen within the body, therefore the nitrogen has to be balanced in the body
2
Q
when does positive nitrogen balance happen
A
If intake exceeds output
- Periods for growth
- Pregnancy -
- tissue repair
3
Q
when does negative nitrogen balance happen
A
If output exceeds input
- indicates body protein breakdown
- Fasting
- Trauma
- Protein malnutrition
- serious tissue wintry
- fever
- wasting diseases
4
Q
what are conditional essential amino acids
A
- Some capacity to make ourselves but if the demand is particularly high then we have to make them from the diet as well
5
Q
what are amino acids used for
A
- 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
6
Q
what amino acids can be used to make what neurotransmitters
A
- 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
7
Q
if you add an amine group on a Keto acid it..
A
becomes an amino acid
8
Q
what amino acid does pyruvate become
A
- Pyruvate (keto acid)becomes alanine (amino acids)
9
Q
what amino acid does alpha ketoglutarate become
A
- Alpha ketoglutarate (keto acid) becomes glutamate (amino acids)
10
Q
what amino acid does oxaloacetate become
A
- Oxaloacetate (keto acid) add an amino group becomes aspartate (amino acids)
11
Q
what vitamins is required for Keto acids to turn into amino acids
A
B6
12
Q
what sub goroup of amino acids are there
A
glutagenic amino acids and ketogenic amino acids
13
Q
what are glutagenic amino acids used for
A
can be used in glyconeogensis to make glucose
14
Q
name some glutagenic amino acids .
A
- alanine
- aspartate
- glutamine
- glutamate
15
Q
what can glutagenic amino acids be used to make
A
- Alanine can be used to make pyruvate
- Asparate can be used to make oxaloacetate
- glutamine and glutamate can be used to make alpha ketoglutarate
16
Q
what are ketogenic amino acids
A
- these are amino acids that can be used to make ketone bodies
17
Q
describe how ketone amino acids are made
A
- 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
18
Q
what are the soles ketogenic amino acids
A
leucine
lysine
19
Q
what ketogenic amino acids can make acetoacetyl-CoA
A
- leucine
- lysine
- phenylalanine
- tyrosine
- tryptophan
20
Q
what keotgneic amino acids can be used to make acetyl-CoA
A
- isoleucine
- leucine
- tryptophan
21
Q
describe how phenylalanine can be converted to glucose
A
- 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
22
Q
what can phenylalanine compensate for
A
- Phenylalaine can compensate for low levels of tyrosine
23
Q
what are the branched chain amino acids
A
leucine isoleucine and valaine
24
Q
how are branch amino acids broken down
A
- 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
25
what is isoleucine broken down into
- Isoleucine to proionylCoA and acetyl CoA
26
what is leucine broken down into
leucine to B-hydroxy-Bmethyl glutaryl CoA and then acetoacetate and acetyl-CoA
27
what is valaine broken down into
- Valine is broken down to succinylCoA
28
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
29
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
30
what happens to excess amino acids in skeletal muscles
- There is excess amino acids being converted into glutamate
31
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
32
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
33
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
34
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
35
what is nitrogen balance
Nitrogen balance is a measure of nitrogen input minus nitrogen output.
Nitrogen Balance = Nitrogen intake - Nitrogen loss
36
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
37
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
38
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
