26 topics with concise breakdowns: definitions, key facts, and seminar questions.
The "Amino Acid Metabolism" section covers the entire pathway of protein nitrogen in the body: from protein digestion in the stomach and intestines to the maintenance of nitrogen balance. Here, we analyze in detail how amino acids lose their amino groups via transamination and deamination reactions, as well as the further fate of their carbon skeleton.
A separate module is dedicated to the specialized metabolism of amino acids (serine, glycine, methionine, histidine, phenylalanine, and tyrosine). You will learn how creatine is synthesized, what role folic acid plays, and how vital biogenic amines, including histamine and GABA, are formed.
What is most frequently asked on exams? A traditional leader in the number of errors is the urea cycle (ornithine cycle) and ammonia metabolism pathways. Be sure to pay attention to the clinical section: hyperammonemia, genetic disorders of phenylalanine and tyrosine metabolism, and the biochemical foundations of Parkinson's disease.
What happens if an essential amino acid is missing from the diet?
The limiting amino acid rule will apply. The absence of even a single essential component will completely disrupt the synthesis of the body's own proteins.
In what forms is nitrogen excreted from the body by the kidneys?
Nitrogen is excreted by the kidneys primarily as urea, as well as part of various nitrogenous salts.
How does rapid pepsinogen activation occur?
Initially, pepsinogen is slowly activated by hydrochloric acid, and then the generated pepsin very rapidly activates the remaining pepsinogen via an autocatalytic mechanism.
Why does the level of AST rise rather than ALT during a myocardial infarction?
AST is an organ-specific enzyme for the heart—its concentration in cardiomyocytes is significantly higher. In myocardial necrosis, this enzyme enters the systemic circulation in large quantities.
How does deamination differ from transamination?
During transamination, the amino group is transferred to a keto acid, so the total number of amino acids does not change. During deamination, the amino group is permanently cleaved as toxic ammonia, and the amino acid pool decreases.
What happens to alanine if dietary intake is low, but starch intake is high?
The level of alanine will be maintained through its endogenous synthesis. Pyruvate derived from carbohydrate breakdown combines with glutamate (the amino group donor) in a reaction catalyzed by the enzyme ALT to form alanine.
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