Module 8 Flashcards
• A state where the amount of nitrogen ingested each day is balanced by the amount excreted, resulting in no net change in the amount of body nitrogen
Nitrogen Balance
Nitrogen intake should equal nitrogen excretion
Nitrogen Metabolism
- Intake > Excretion
* Net accumulation of proteins as in growth and pregnancy
Positive Nitrogen Balance
• Intake
Negative Nitrogen Balance
– refers to Protein synthesis and degradation
–300-400 g per day
– Amount of protein degraded and resynthesized from Amino Acid
Protein Turnover
–Sum of all free amino acids in cells and ECF
–Three possible sources:
•Degradation and turnover of body protein
•Dietary intake
•Synthesis of nonessential amino acids
Amino Acid Pool
Remember that proteins have __, so this is the logic behind high protein diets»_space; protein comprise the calories in the diet, but are degraded eventually
no storage form
MARKING: __ binds to endogenous protein (proteins that are created intracellularly) that needs to be degraded by proteosome pathway ( GRABAGE disposal) energy dependent manner) – alpha carboxyl of glycine of ubiquitin to lysine amino group of protein substrate
Ubiquitin-proteosome mechanism (energy dependent)
> > degraded in the lysosomes (non-energy dependent manner)
Exogenous (extracellular)
Digestion of protein begins in the stomach with __
HCl and Pepsin
Digestion by pancreatic enzymes that are initially secreted as zymogens. __ is the common activator.
Trypsin
__ in the brush border liberate amino acids and dipeptides
Aminopeptidase
Free amino acids are absorbed by __
secondary active transport
Can you name other substances absorbed by secondary active transport in the small intestine?
glucose and galactose
After absorbing the products of protein digestion, which of the following products can you see inside enterocytes?
Dipeptides and tripeptides are also absorbed into the GIT, not just amino acids.
- The presence of an alpha-amino group keeps amino acids safely locked away from oxidative breakdown
- Removing the alpha amino group»_space; OBLIGATORY step in the catabolism of all Amino Acid
Amino Acid Catabolism
Remember that the presence of an alpha amino group keeps the AA safe from breakdown»_space; therefore its removal is an OBLIGATORY step in the catabolism of AA
- 1st phase: throw away amino group sa urea cycle
* 2nd phase: recycle whats left of aa
First Phase of Amino Acid Catabolism
Removal of the α-amino group (a process called deamination) forming ammonia and a corresponding α-ketoacid
(First Phase of Amino Acid Catabolism)
What happens to ammonia?
- Maybe excreted as free ammonia in urine and stool
- Majority is converted to urea before being excreted in urine (urea is the major disposal form of nitrogen)
Second Phase of Amino Acid Catabolism
Carbon skeletons of α-ketoacids are converted to common intermediates of energy-producing metabolic pathways
- Glycolysis
- Krebs Cycle
(Excretion of Excess Nitrogen)
–seen in telostean fish, which excrete highly toxic ammonia
Ammonotelic
(Excretion of Excess Nitrogen)
–seen in land animals, including humans, who excrete non-toxic, water-soluble urea
Ureotelic
(Excretion of Excess Nitrogen)
–seen in birds, which excrete uric acid as semisolid guano
Uricotelic
__ is relatively move toxic than uric acid, that’s why is has to be diluted in urine in the body. Uric acid is not very toxic, and may be concentrated to a semi-solid paste without causing toxic effects.
Urea