science

Xylose

Xylose 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 Xylose rather than just read about it. In short: Xylose (cf. Ancient Greek: ξύλον, xylon, "wood") is a common monosaccharide, i.e. a simple sugar.

Key takeaways

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

Reference excerpt

Xylose (cf. Ancient Greek: ξύλον, xylon, "wood") is a common monosaccharide, i.e. a simple sugar. Xylose is classified as aldopentose type, which means that it contains five carbon atoms and includes an aldehyde functional group, at least in its open-chain form. It is abundant in biomass, and is one of the most abundant sugars in nature. It is a white, water-soluble solid.

Structure The acyclic form of xylose has chemical formula HOCH2(CH(OH))3CHO. Cyclic hemiacetal isomers are more prevalent in solution. These cyclic isomers include the pyranoses feature six-membered C5O rings, and the furanoses, which feature five-membered C4O rings (with a pendant CH2OH group). Each of these rings is subject to further isomerism, depending on the relative orientation of the anomeric hydroxy group. The dextrorotary form, d-xylose, is the one that usually occurs endogenously in living things. A levorotary form, l-xylose, can be synthesized.

Occurrence Xylose is the main building block for the hemicellulose xylan, which comprises about 30% of some plants (birch for example), far less in others (spruce and pine have about 9% xylan). Xylose is otherwise pervasive, being found in the embryos of most edible plants. It was first isolated from wood by Finnish scientist, Koch, in 1881, but first became commercially viable, with a price close to sucrose, in 1930. Xylose is also the first saccharide added to the serine or threonine in the proteoglycan type O-glycosylation, and, so, it is the first saccharide in biosynthetic pathways of most anionic polysaccharides such as heparan sulfate and chondroitin sulfate. Xylose is also found in some species of Chrysolinina beetles, including Chrysolina coerulans. They have cardiac glycosides (including xylose) in their defensive glands.

Applications

Chemicals The acid-catalysed degradation of hemicellulose gives furfural, a precursor to synthetic polymers and to tetrahydrofuran.

Human consumption Xylose is not a major human nutrient and is largely excreted by the kidneys. An oxidoreductase pathway is present in eukaryotic microorganisms. Humans have enzymes called protein xylosyltransferases (XYLT1, XYLT2) which transfer xylose from UDP to a serine in the core protein of proteoglycans.

Animal medicine In animal medicine, xylose is used to test for malabsorption by administration in water to the patient after fasting. If xylose is detected in blood and/or urine within the next few hours, it has been absorbed by the intestines. High xylose intake on the order of approximately 100 g/kg of animal body weight is relatively well tolerated in pigs, and in a similar manner to results from human studies, a portion of the xylose ingested is excreted in urine unmodified.

Derivatives Reduction of xylose by catalytic hydrogenation produces the sugar alcohol xylitol, which provides about 2.4 calories per gram, and is used as a sweetener.

See also Saccharophagus degradans Xylonic acid Xylose metabolism Xylitol

References

Illustrations

Worked examples

Example 1 — a first encounter with Xylose

Start with the simplest possible case. Write down what Xylose 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 Xylose 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 Xylose 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 Xylose

In research: Xylose 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 Xylose 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: Xylose is common in secondary-school and first-year university syllabi. It links to neighbouring topics Aldopentoses, Dietary fiber, Furanoses, so understanding it makes those chapters shorter.
In everyday life: Look for Xylose 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 Xylose in 20 minutes

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

Frequently asked questions

What is Xylose in simple terms?

Xylose (cf. Ancient Greek: ξύλον, xylon, "wood") is a common monosaccharide, i.e. a simple sugar.

Why does Xylose 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 Xylose?

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 Xylose.