What is significant about the core structure of a steroid molecule?

Submitted by AGrandmother t3_xxi7q2 in askscience

I understand that a molecule is classified as a steroid if it contains the four-ring core circled here. I'm wondering, why is this a common or significant property for an organic compound to have?

Does this core structure interact with other molecules in a specific way? Is the core structure common because of how it's synthesized?

Thanks in advance for any insight!

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[deleted] t1_irdvmzs wrote

[deleted]

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AGrandmother OP t1_ireb33x wrote

This helps a lot, thank you!

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heteromer t1_irekry8 wrote

The 4 ringed structure also helps improve lipophilicity of the molecule, which is especially important because steroids need to cross the membrane into the cytoplasm to bind to nuclear receptors. They also help stabilize the molecule into a planar structure to facilitate membrane penetration.

Other ligands of nuclear receptors are produced from Acetyl CoA, like cholecalciferol (vitamin D3) and retinoids. As with nuclear receptors, steroids have a long genetic history. It seems estrogen receptors were among the first steroid receptors to appear, and mutations brought about more diverse roles for steroids.

Here is a nice article I found

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slouchingtoepiphany t1_ire5rza wrote

Steroid molecules are derived from a common precursor, cholesterol, the base molecule in the illustration. They share similar chemical properties, notably their lipophilicity, which enables them to pass through cellular membranes without the need for a carrier molecule. Indeed, cholesterol is a normal constituent of cellular membranes. The conversion of cholesterol into the various steroids (e.g., cell-specific enzymes add molecules to the numbered sites on your example). The subsequent MOA of these steroids is similar. They circulate in the blood, pass through the membranes of target cells, bind (dimerize) to intracellular receptors, bind to DNA regulatory elements, and up- or down-regulate gene expression to yield proteins that influence the organism's physiology.

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