science

Melatonin

Melatonin 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 Melatonin rather than just read about it. In short: Melatonin, an indoleamine, is a natural compound produced by various organisms, including bacteria and eukaryotes. Its discovery in 1958 by Aaron B.

Key takeaways

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

Reference excerpt

Melatonin, an indoleamine, is a natural compound produced by various organisms, including bacteria and eukaryotes. Its discovery in 1958 by Aaron B. Lerner and colleagues stemmed from the isolation of a substance from the pineal gland of cows that could induce skin lightening in common frogs. This compound was later identified as a hormone secreted in the brain during the night, playing a crucial role in regulating the sleep-wake cycle, also known as the circadian rhythm, in vertebrates. In vertebrates, melatonin's functions extend to synchronizing sleep-wake cycles, encompassing sleep-wake timing and blood pressure regulation, as well as controlling seasonal rhythmicity (circannual cycle), which includes reproduction, fattening, molting, and hibernation. Its effects are mediated through the activation of melatonin receptors and its role as an antioxidant. In plants and bacteria, it serves as a defense mechanism against oxidative stress, indicating its evolutionary significance. Mitochondria, key organelles, are the main producers of melatonin, underscoring its "ancient origins" and its fundamental role in protecting the earliest cells from reactive oxygen species. In addition to its endogenous functions as a hormone and antioxidant, melatonin is also administered exogenously as a dietary supplement and medication. Melatonin is used medically primarily for sleep-related problems: for example, prolonged-release melatonin (Circadin) is approved in several countries for short-term treatment of insomnia in people aged 55 years of age or older. It is used in the treatment of sleep disorders, including insomnia and various circadian rhythm sleep disorders.

Numerous studies suggest that disruption of melatonin production may underlie the association between light exposure before and during sleep and impaired sleep quality. It has also been suggested that light-induced disruption of melatonin production may potentially affect cognitive, emotional, cardiovascular, and metabolic functions.

Biological activity In humans, melatonin is presumed to act as a full agonist of two types of melatonin receptors: melatonin receptor 1, with picomolar binding affinity, and melatonin receptor 2, with nanomolar binding affinity. Both receptors are part of the G-protein coupled receptors (GPCRs) family, specifically the Gi/o alpha subunit GPCRs. In vitro, melatonin functions as a high-capacity antioxidant or free radical scavenger within mitochondria, playing a dual role in combating cellular oxidative stress. First, it directly neutralizes free radicals, and second, it promotes the gene expression of essential antioxidant enzymes, such as superoxide dismutase, glutathione peroxidase, glutathione reductase, and catalase. This increase in antioxidant enzyme expression is mediated through signal transduction pathways activated by the binding of melatonin to its receptors. Through these mechanisms, melatonin is presumed to protect cells against oxidative stress in ways beyond regulating the sleep-wake cycle.

Biological functions

Circadian rhythm

In mammals, melatonin is critical for the regulation of sleep–wake cycles, or circadian rhythms. The establishment of regular melatonin levels in human infants occurs around the third month after birth, with peak concentrations observed between midnight and 8:00 am. It has been documented that melatonin production diminishes as a person ages. Additionally, a shift in the timing of melatonin secretion is observed during adolescence, resulting in delayed sleep and wake times, increasing their risk for delayed sleep phase disorder during this period. In adults, approximately 30 μg of melatonin is synthesized per day, nearly 80% of which occurs at night. The antioxidant properties of melatonin were first recognized in 1993. In vitro studies reveal that melatonin directly neutralizes various reactive oxygen species, including hydroxyl (OH•), superoxide (O2−•), and reactive nitrogen species such as nitric oxide (NO•). In plants, melatonin works synergistically with other antioxidants, enhancing the overall effectiveness of each antioxidant. This compound has been found to be twice as efficacious as vitamin E, a known potent lipophilic antioxidant, at scavenging peroxyl radicals. The promotion of antioxidant enzyme expression, such as superoxide dismutase, glutathione peroxidase, glutathione reductase, and catalase, is mediated through melatonin receptor-triggered signal transduction pathways. Melatonin's concentration in the mitochondrial matrix is significantly higher than that found in the blood plasma, emphasizing its role not only in direct free radical scavenging but also in modulating the expression of antioxidant enzymes and maintaining mitochondrial integrity. This multifaceted role shows the physiological significance of melatonin as a mitochondrial antioxidant, a notion supported by numerous scholars. Furthermore, the interaction of melatonin with reactive oxygen and nitrogen species results in the formation of metabolites capable of reducing free radicals. These metabolites, including cyclic 3-hydroxymelatonin, N1-acetyl-N2-formyl-5-methoxykynuramine (AFMK), and N1-acetyl-5-methoxykynuramine (AMK), contribute to the broader antioxidative effects of melatonin through further redox reactions with free radicals.

Immune system Melatonin's interaction with the immune system is recognized, yet the specifics of these interactions remain inadequately defined. An anti-inflammatory effect appears to be the most significant. The efficacy of melatonin in disease treatment has been the subject of limited trials, with most available data deriving from small-scale, preliminary studies. It is posited that any beneficial immunological impact is attributable to melatonin's action on high-affinity receptors (MT1 and MT2), which are present on immunocompetent cells. Preclinical investigations suggest that melatonin may augment cytokine production and promote the expansion of T cells, thereby potentially mitigating acquired immunodeficiencies.

Weight regulation Melatonin's potential to regulate weight gain is posited to involve its inhibitory effect on leptin, a hormone that serves as a long-term indicator of the body's energy status.

Biochemistry

Biosynthesis

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Melatonin

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

In research: Melatonin 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 Melatonin 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: Melatonin is common in secondary-school and first-year university syllabi. It links to neighbouring topics 5-Methoxytryptamines, Melatonin, Melatonin receptor agonists, so understanding it makes those chapters shorter.
In everyday life: Look for Melatonin 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 Melatonin in 20 minutes

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

Frequently asked questions

What is Melatonin in simple terms?

Melatonin, an indoleamine, is a natural compound produced by various organisms, including bacteria and eukaryotes. Its discovery in 1958 by Aaron B.

Why does Melatonin 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 Melatonin?

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 Melatonin.