Protein Breakdown and Urea Formation
This lecture focuses on
- How AA are fed into TCA cycle and can be used for gluconeogenesis
- The formation of ammonia/ammonium ions
- How it disposes it, the urea cycle and its relationship to the TCA cycle
In the body, there is a very simple principle:
Growth = Synthesis – Breakdown
This equation applies for all aspects of the body, be it individual proteins, single cells,
whole tissues or the whole body.
Nitrogen Balance
We intake proteins through our diet, there are no specific protein stores in our body.
Proteins are either structural or functional, excess protein is broken down and
excreted.
So generally there should be a balance between input and output.
If we are in positive nitrogen balance, this means the amount of protein/AA we retain
exceeds the amount that is broken down and excreted. This is a normal process and
occurs in things like growth.
The opposite is negative nitrogen balance when input is superseded by breakdown.
, We ingest dietary protein which is broken down into AA, there are then a number of
fates of these AAs.
They can be used to make new protein e.g. muscle fibres, enzymes (structural or
functional).
At the same time there are also proteins being broken down and when in nitrogen
balance this breakdown matches the synthesis. Out input is about 100g a day and
output 100g a day.
The nitrogen is removed in the liver through formation of urea. All this can be seen
below.
In a normal, healthy individual the relationship should be balanced and look like
below:
This lecture focuses on
- How AA are fed into TCA cycle and can be used for gluconeogenesis
- The formation of ammonia/ammonium ions
- How it disposes it, the urea cycle and its relationship to the TCA cycle
In the body, there is a very simple principle:
Growth = Synthesis – Breakdown
This equation applies for all aspects of the body, be it individual proteins, single cells,
whole tissues or the whole body.
Nitrogen Balance
We intake proteins through our diet, there are no specific protein stores in our body.
Proteins are either structural or functional, excess protein is broken down and
excreted.
So generally there should be a balance between input and output.
If we are in positive nitrogen balance, this means the amount of protein/AA we retain
exceeds the amount that is broken down and excreted. This is a normal process and
occurs in things like growth.
The opposite is negative nitrogen balance when input is superseded by breakdown.
, We ingest dietary protein which is broken down into AA, there are then a number of
fates of these AAs.
They can be used to make new protein e.g. muscle fibres, enzymes (structural or
functional).
At the same time there are also proteins being broken down and when in nitrogen
balance this breakdown matches the synthesis. Out input is about 100g a day and
output 100g a day.
The nitrogen is removed in the liver through formation of urea. All this can be seen
below.
In a normal, healthy individual the relationship should be balanced and look like
below:
