science

Parietin

Parietin is a science 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 Parietin rather than just read about it. In short: Parietin, or physcion, is the predominant cortical pigment of lichens in the genus Caloplaca, a secondary product of the lichen Xanthoria parietina, and a pigment found in the roots of curled dock (Rumex crispus). It has an orange-yellow color and absorbs blue light.

Key takeaways

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

Reference excerpt

Parietin, or physcion, is the predominant cortical pigment of lichens in the genus Caloplaca, a secondary product of the lichen Xanthoria parietina, and a pigment found in the roots of curled dock (Rumex crispus). It has an orange-yellow color and absorbs blue light. Parietin has also been shown to protect lichens against UV-B light, at high altitudes in alpine regions. The UV-B light stimulates production of parietin, protecting the lichens from damage. Lichens in arctic regions such as Svalbard retain this capability though they do not encounter damaging levels of UV-B, a capability that could help protect the lichens in case of ozone layer thinning. It has also shown antifungal activity against barley powdery mildew and cucumber powdery mildew, more efficiently in the latter case than treatments with fenarimol and polyoxin B. It reacts with KOH to form a deep, reddish-magenta compound.

Effect on human cancer cells Also found in rhubarb, the orange compound appears to have potential to suppress 6-phosphogluconate dehydrogenase, or 6PGD. 6PGD is the third enzyme of the pentose phosphate pathway, or PPP, an oxidative process fueling growth in a still-relatively-unknown way. But it appears that arresting the chemical machinery at its third step could be promising for oncology. The parietin, identified from an FDA database of 2,000 known suppressors of 6PGD, killed half the human leukemia cells over two days in the laboratory. The pigment also slowed the growth of other human cancer cells in mouse models, according to the study. A more-potent derivative of the parietin called S3 may even cut the growth of lung cancer cells implanted in mice by two-thirds, over the course of 11 days. The compound also appears to be non-toxic to healthy cells.

References

Further reading Caloplaca coralloides chemistry Edwards, Howell G. M.; Emma M. Newton; David D. Wynn-Williams; Steven R. Coombes (2003-03-12). "Molecular spectroscopic studies of lichen substances 1: parietin and emodin". Journal of Molecular Structure. 648 (1–2): 49–59. Bibcode:2003JMoSt.648...49E. doi:10.1016/S0022-2860(02)00384-8. Solhaug, Knut A.; Yngvar Gauslaa (November 1996). "Parietin, a photoprotective secondary product of the lichen Xanthoria parietina". Oecologia. 108 (3): 412–418. Bibcode:1996Oecol.108..412S. doi:10.1007/BF00333715. PMID 28307855. S2CID 34925113.

Illustrations

Worked examples

Example 1 — a first encounter with Parietin

Start with the simplest possible case. Write down what Parietin claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, 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 Parietin 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 Parietin 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 Parietin

In research: Parietin appears in science 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 Parietin 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: Parietin is common in secondary-school and first-year university syllabi. It links to neighbouring topics Anthraquinone dyes, Antifungals, Dihydroxyanthraquinones, so understanding it makes those chapters shorter.
In everyday life: Look for Parietin 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 Parietin in 20 minutes

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

Frequently asked questions

What is Parietin in simple terms?

Why does Parietin matter?

Because it connects several science 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 Parietin?

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 Parietin.