chemistry

Homogentisic acid

Homogentisic acid 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 Homogentisic acid rather than just read about it. In short: Homogentisic acid (2,5-dihydroxyphenylacetic acid) is a phenolic acid usually found in Arbutus unedo (strawberry-tree) honey. It is also present in the bacterial plant pathogen Xanthomonas campestris pv. phaseoli as well as in the yeast Yarrowia lipolytica where it is associated with the production of brown pigments.

Key takeaways

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

Reference excerpt

Homogentisic acid (2,5-dihydroxyphenylacetic acid) is a phenolic acid usually found in Arbutus unedo (strawberry-tree) honey. It is also present in the bacterial plant pathogen Xanthomonas campestris pv. phaseoli as well as in the yeast Yarrowia lipolytica where it is associated with the production of brown pigments. It is oxidatively dimerised to form hipposudoric acid, one of the main constituents of the 'blood sweat' of hippopotamuses. It is less commonly known as melanic acid, the name chosen by William Prout.

Human pathology Accumulation of excess homogentisic acid and its oxide, named alkapton, is a result of the failure of the enzyme homogentisic acid 1,2-dioxygenase (typically due to a mutation) in the degradative pathway of tyrosine, consequently associated with alkaptonuria.

Intermediate It is an intermediate in the catabolism of aromatic amino acids such as phenylalanine and tyrosine. 4-Hydroxyphenylpyruvate (produced by transamination of tyrosine) is acted upon by the enzyme 4-hydroxyphenylpyruvate dioxygenase to yield homogentisate. If active and present, the enzyme homogentisate 1,2-dioxygenase further degrades homogentisic acid to yield 4-maleylacetoacetic acid.

References

Illustrations

Worked examples

Example 1 — a first encounter with Homogentisic acid

Start with the simplest possible case. Write down what Homogentisic acid 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 Homogentisic acid 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 Homogentisic acid 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 Homogentisic acid

In research: Homogentisic acid 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 Homogentisic acid 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: Homogentisic acid is common in secondary-school and first-year university syllabi. It links to neighbouring topics Biochemical reactions, Hydroquinones, Hydroxycarboxylic acids, so understanding it makes those chapters shorter.
In everyday life: Look for Homogentisic acid 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 Homogentisic acid in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Homogentisic acid 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 Homogentisic acid out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Homogentisic acid in simple terms?

Why does Homogentisic acid 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 Homogentisic acid?

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 Homogentisic acid.