chemistry

Organic acidemia

Organic acidemia is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Organic acidemia rather than just read about it. In short: Organic acidemia is a term used to classify a group of metabolic disorders which disrupt normal amino acid metabolism, particularly branched-chain amino acids, causing a buildup of acids which are usually not present. The branched-chain amino acids include isoleucine, leucine and valine.

Key takeaways

Organic acidemia belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Organic acidemia to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Organic acidemia from memory before moving on to harder problems.

Reference excerpt

Organic acidemia is a term used to classify a group of metabolic disorders which disrupt normal amino acid metabolism, particularly branched-chain amino acids, causing a buildup of acids which are usually not present. The branched-chain amino acids include isoleucine, leucine and valine. Organic acids refer to the amino acids and certain odd-chained fatty acids which are affected by these disorders. The four main types of organic acidemia are: methylmalonic acidemia, propionic acidemia, isovaleric acidemia, and maple syrup urine disease.

Cause Most of the organic acidemias result from defective autosomal genes for various enzymes important to amino acid metabolism. Neurological and physiological harm is caused by this impaired ability to synthesize a key enzyme required to break down a specific amino acid, or group of amino acids, resulting in acidemia and toxicity to specific organ systems. Most are inherited as autosomal recessive diseases.

Diagnosis Organic acidemias are usually diagnosed in infancy, characterized by urinary excretion of abnormal amounts or types of organic acids. The diagnosis is usually made by detecting an abnormal pattern of organic acids in a urine sample by gas chromatography-mass spectrometry. In some conditions, the urine is always abnormal, in others, the characteristic substances are only present intermittently. Many of the organic acidemias are detectable by newborn screening with tandem mass spectrometry. These disorders vary in their prognosis, from manageable to fatal, and usually affect more than one organ system, especially the central nervous system. Neurological damage and developmental delay are common factors in diagnosis, with associated symptoms ranging from poor feeding to slow growth, lethargy, vomiting, dehydration, malnutrition, hypoglycemia, hypotonia, metabolic acidosis, ketoacidosis, hyperammonemia, and if left untreated, death.

Treatment Treatment or management of organic acidemias vary; e.g. see methylmalonic acidemia, propionic acidemia, isovaleric acidemia, and maple syrup urine disease. As of 1984 there were no effective treatments for all of the conditions, though treatment for some included a limited protein/high carbohydrate diet, intravenous fluids, amino acid substitution, vitamin supplementation, carnitine, induced anabolism, and in some cases, tube-feeding. As of 1993 beta-ketothiolase deficiency and other OAs were managed by trying to restore biochemical and physiologic homeostasis; common therapies included restricting diet to avoid the precursor amino acids and use of compounds to either dispose of toxic metabolites or increase enzyme activity.

See also ACAT1 § Ketothiolase deficiency, another type of OA

References

External links

GeneReviews/UW/NIH entry on Organic acidemias

Worked examples

Example 1 — a first encounter with Organic acidemia

Start with the simplest possible case. Write down what Organic acidemia claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Organic acidemia before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Organic acidemia ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Organic acidemia

In research: Organic acidemia appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Organic acidemia in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Organic acidemia is common in secondary-school and first-year university syllabi. It links to neighbouring topics Amino acid metabolism disorders, Rare diseases, so understanding it makes those chapters shorter.
In everyday life: Look for Organic acidemia outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Organic acidemia in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Organic acidemia means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Organic acidemia out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Organic acidemia in simple terms?

Why does Organic acidemia matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Organic acidemia?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Organic acidemia.