Type: Prelims Only

Why in the News?

Semaglutide, a drug originally developed for type 2 diabetes but also highly effective for weight reduction has been added to the WHO’s Model List of Essential Medicines (EML).

About WHO’s Model List of Essential Medicines (EML):

• What is it: A global reference by WHO listing the most effective, safe, and essential medicines for priority healthcare needs.
• History: First introduced in 1977 to improve access in developing countries; updated every 2 years by a WHO Expert Committee.
• Structure:
  • Core list: Basic medicines usable with limited infrastructure.
  • Complementary list:  Need specialised training, facilities, or are costlier.
• Global Impact: Over 150 countries use EML to build national lists for procurement, reimbursement, and universal health coverage (UHC).
• Selection Criteria:
  • Public health relevance.
  • Proven efficacy and safety.
  • Cost-effectiveness compared to alternatives.
  • Quality, stability, and reliable formulations.
  • Preference for single-compound formulations unless combinations are better.

Why in the News?

A recent study published in the Nature suggests that simple molecules called aminoacyl-thiols may have helped amino acids stick to RNA (ribonucleic acid) without enzymes, giving clues to how protein-making began on early Earth.

About the RNA–Amino Acid Link:

• Discovery: Study showed that aminoacyl-thiols (simple prebiotic molecules) can attach amino acids to RNA directly (aminoacylation) without enzymes.
• Modern Parallel: In cells today, this is done by aminoacyl-tRNA synthetases before ribosomes build proteins. This created the “chicken-and-egg problem”: proteins are needed to make proteins.
• Chemical Mechanism:
  • Thioesters: Enable amino acids to attach to RNA (“charging RNA”).
  • Thioacids: Enable amino acids to link into peptides.
• Robustness: Works at neutral pH, across many amino acids, with unexpected selectivity for RNA despite other molecules being more reactive.

Significance for Origin of Life:

• RNA World Hypothesis: Supports the idea that RNA and amino acids interacted directly before enzymes evolved.
• Chemical Advantage: Shows RNA had a natural edge in early Earth conditions, explaining its central role in life’s origin.
• Prebiotic Plausibility: Aminoacyl-thiols could form from simple nitriles and thiols, and reactions occurred even in cold/frozen pools resembling early Earth.
• Evolutionary Pathway: Suggests life began with short peptides, with RNA later evolving control, leading to coded protein synthesis and ribosomes.