Nitrogen Flashcards
Does not cover inherited metabollic diseases
What is the process in which nitrogen is converted to Ammonium?
Fixation
What is nitrification?
NH4+ to nitrite and nitrate
We can get our Nitrogen from nitrate/nitrate
What amino acid is central to nitrogen entering our body?
Glutamate
What process is central to us conserving the nitrogen in our bodies?
Transamination
- transferring amino acids between molecules
Give a general equation for transamination.
Amino acid 1 + keto acid 2 —-> Keto acid 1 + amino acid 2
What is formed when glutamate undergoes transamination with a keto acid?
Alpha-Ketoglutarate
Transamination reactions are readily reversible.
Why is this useful, in terms of how our body processes amino acids.
Can take part in both synthesis and degradation of amino acids
Pyridoxal phosphate cofactor is needed by what type of enzyme?
Aminotransferases
transamination enzyme
Pyridoxal phosphate cofactor (PLP) is derived from what essential vitamin?
B6
Amino acids undergo oxidative catabolism under 3 conditions.
What are they?
Leftover amino acids from normal protein turnover
Excess from diet
Stored proteins are broken down when carbohydrates are in short supply
What is pepsin and where does it function?
Enzyme - hydrolyses protein chains
Stomach
Trypsin and chymotrypsin cut proteins and larger peptides into smaller peptides, but where do they do this?
Small intestine
What enzymes hydrolyse peptides into amino acids, and where do they do this?
Aminopeptidase
Carboxypeptidases A & B
Small intestine
True or false
Peptides/proteins must be degraded to amino acids before they can cross through the epithelial cells and into the blood.
False
Amino acids, dipeptides and tripeptides can cross into the epithelial cells
But only single amino acids can go into the blood
What is ubiquitin used for?
Marks proteins that need to be degraded
Why are excess proteins/amino acids degraded and not stored like fats/sugars?
No storage for excess protein
How do humans excrete nitrogen?
Urea + uric acid
Ammonia is kinda toxic n stuff
How is it safely transported in the blood?
As glutamine or alanine
Where is excess glutamine processed?
3
Intestines
Kidneys
Liver
Ammonia + pyruvate = ?
Alanine
Muscles exercising vigorously work anaerobically.
This would cause a problem in the muscles if it was not for glutamate. What is the problem, and how does glutamate solve it?
Anaerobic ∴ glycolysis
∴ pyruvate produced which cannot be broken down anaerobically
∴ lactate would build up
glutamate can donate ammonia, to make alanine from the pyruvate
alanine transported to liver ∴ no lactate build up
Proteins can be broken down in exercising muscles if needed.
What cycle is central to protein break down?
Glucose - alanine cycle
In the glucose - alanine cycle, why is glutamate converted to glutamine/alanine, only to be converted back to glutamate later on?
Glutamate is negatively charged
∴ can’t be transported to the liver
What happens to excess glutamate?
Metabolised in mitochondria of hepatocytes
When excess glutamate is metabolised, what happens to ammonia/nitrogen?
Re-captured via synthesis of carbamoyl phosphate
Carbamoyl phosphate then goes into the urea cycle
Through processes such as the glucose - alanine cycle, carbon skeletons are produced from amino acids.
How are these carbon skeletons used?
Converted to glucose
Oxidised in CAC
Converted to ketones/fats
Why are amino acids useful in terms of the citric acid cycle?
Enter as intermediates
Carbon skeletons
Describe what the terms glucogenic and ketogenic mean.
Some amino acids ‘feed’ into gluconeogenesis (glucogenic) and some ‘feed’ into the acetyl CoA (ketogenic)
Some amino acids are both glucogenic and ketogenic
Describe the fates of ketogenic amino acids.
CAC
Ketone bodies
What nitrogen containing molecule is used in the second nitrogen acquiring reaction of the urea cycle?
Aspartate
What are the possible fates of carbon skeletons produced from amino acid degradation?
Citric acid cycle - catabolism
Gluconeogenesis
Ketogenesis
What are the possible fates of ammonia produced by amino acid degradation?
Biosynthesis
Excretion via Urea cycle
Why are molecules like glutamate and aspartate not suitable for tranpsort in the blood?
They are charged
Glutamine and alanine are uncharged so are much more suitable
