What is the primary role of amino acids in human metabolism?
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Examines amino acid pathways, nitrogen balance, and clinical conditions like urea cycle defects.
Mastering this deck enables a thorough understanding of amino acid processing, nitrogen excretion, and the clinical implications of urea cycle disorders, facilitating accurate diagnosis and effective management of metabolic conditions.
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| # | Front | Back | Hint |
|---|---|---|---|
| 1 | What is the primary role of amino acids in human metabolism? | Amino acids serve as building blocks for proteins, precursors for neurotransmitters and hormones, and can be used as energy sources when necessary. | Think of amino acids as the body's versatile building blocks and precursors. |
| 2 | Which amino acid is exclusively ketogenic and cannot be glucogenic? | Lysine and leucine are exclusively ketogenic amino acids; they are only converted into ketone bodies, not glucose. | Remember 'Lysine and Leucine' both start with 'L' and are ketogenic only. |
| 3 | What is transamination and why is it important in amino acid metabolism? | Transamination is the transfer of an amino group from an amino acid to a keto acid, facilitating amino acid breakdown and synthesis; it is essential for nitrogen disposal and amino acid interconversion. | Think of transamination as the amino group's 'transfer' or 'swap' process. |
| 4 | Which enzyme catalyzes the first step in amino acid transamination? | Aminotransferases, such as alanine aminotransferase (ALT) and aspartate aminotransferase (AST), catalyze transamination reactions. | Remember ALT and AST are common clinical enzymes involved in amino acid metabolism. |
| 5 | What is the primary nitrogen excretion product in humans? | Urea, which is synthesized in the liver and excreted by the kidneys. | Think of the urea cycle as the body's nitrogen 'detox' pathway. |
| 6 | Where does the urea cycle primarily occur? | In the mitochondria and cytosol of hepatocytes (liver cells). | Remember 'liver' is the site, with mitochondrial involvement at the start. |
| 7 | Which amino acids are directly involved in the urea cycle as nitrogen donors? | Aspartate and ammonia (NH₃) are directly incorporated into the urea cycle. | Aspartate provides nitrogen directly; ammonia is the primary nitrogen waste. |
| 8 | What is the clinical significance of elevated plasma ammonia levels? | Hyperammonemia can cause neurological symptoms, coma, and is often due to urea cycle disorders or liver failure. | High ammonia is neurotoxic—think of 'ammonia as a brain poison' in excess. |
| 9 | Name a common inherited urea cycle disorder and the enzyme affected. | Ornithine transcarbamoylase (OTC) deficiency is the most common inherited urea cycle disorder. | OTC deficiency is X-linked—remember 'OTC' as the key enzyme. |
| 10 | What are typical clinical features of a urea cycle disorder in neonates? | Poor feeding, vomiting, lethargy, seizures, and early death if untreated due to hyperammonemia. | Early signs include neurological deterioration caused by ammonia toxicity. |
| 11 | How does a deficiency of carbamoyl phosphate synthetase I (CPSI) affect the urea cycle? | It impairs the initial step of the cycle, leading to hyperammonemia and orotic aciduria due to pyrimidine pathway shunting. | CPSI deficiency affects the first step—think of it as the cycle's 'gatekeeper'. |
| 12 | What is the significance of orotic aciduria in urea cycle disorders? | Orotic aciduria indicates a block at the CPSI step, causing excess carbamoyl phosphate to be diverted to pyrimidine synthesis. | Orotic acid levels help differentiate between CPSI deficiency and OTC deficiency. |
| 13 | Which amino acids are glucogenic and can contribute to glucose synthesis? | Alanine, glutamine, glutamate, serine, and others are glucogenic amino acids. | Think of 'G' for glucogenic—Alanine and Glutamine are prime examples. |
| 14 | What is the role of glutamine in nitrogen transport? | Glutamine acts as a nitrogen carrier from peripheral tissues to the liver for urea synthesis. | Glutamine is the body's 'nitrogen shuttle'. |
| 15 | How does a deficiency in argininosuccinate synthetase manifest clinically? | It causes citrullinemia, characterized by elevated citrulline levels, hyperammonemia, and neurological symptoms. | Citrullinemia is associated with increased citrulline in blood. |
| 16 | What is the primary treatment strategy for urea cycle disorders? | Reducing protein intake, supplementing with arginine or citrulline, and using ammonia scavengers to facilitate nitrogen excretion. | Aim to lower nitrogen load and enhance alternative excretion pathways. |
| 17 | Name an ammonia scavenger drug used in urea cycle disorders. | Sodium phenylbutyrate or sodium benzoate are commonly used ammonia scavengers. | These drugs help remove excess nitrogen via alternative pathways. |
| 18 | Why is arginine supplementation beneficial in certain urea cycle disorders? | Arginine provides substrate for residual enzyme activity and promotes excretion of nitrogenous waste as argininosuccinate. | Think of arginine as a 'helper' molecule in nitrogen disposal. |
| 19 | What is a typical biochemical finding in orotic aciduria? | Elevated urinary orotic acid levels. | Orotic aciduria points to a block early in the urea cycle or pyrimidine pathway. |
| 20 | Explain the concept of nitrogen balance in amino acid metabolism. | Nitrogen balance refers to the equilibrium between nitrogen intake (via dietary proteins) and nitrogen excretion (mainly as urea); positive balance occurs during growth, negative during starvation. | Balance = intake minus excretion. |
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