there are double rings in the purine bases and there is only a single ring in the pyrimidine base.
Purines because purines have two rings where as pyrimidines have only one ring.
It really depends on what you require from it.
Glucose has 6 carbons in its ring structure, so it forms a 6-membered ring. This means glucose has 6 sides in its ring structure.
Monosaccharides primarily exist in cyclic forms, which are known as ring conformations. The two most common forms are the pyranose (six-membered ring) and furanose (five-membered ring) structures. In pyranose forms, the anomeric carbon can adopt either the alpha or beta configuration, depending on the orientation of the hydroxyl group relative to the CH2OH group. These ring forms can also exhibit different chair or boat conformations, influencing their stability and reactivity.
No. It contains naphazoline, which is kinda sorta but not very much like a steroid. It has a five membered ring and two six membered rings it it (steroids have three six membered rings and one five membered rings). However, the five membered ring in naphazoline contains nitrogen (that in steroids does not) and the six membered rings are aromatic (those in steroids or not). So it's not a steroid, but if you were to glance at a spacefilling model and weren't a chemist I can see how you might mistake it for one.
pyranose is a collective noun of carbohydrates that have a six membered ring system which is 5 carbons and one oxygen. example: glucose Furanose is a collective noun of carbohydrates that have a five membered ring system which is 4 carbons and one oxygen. example: fructose
For the molecular formula C7H14O with a five-membered ring and a tertiary alcohol group, there are a limited number of isomers. A tertiary alcohol requires the hydroxyl (-OH) group to be attached to a carbon that is itself bonded to three other carbons. Given the constraints of forming a five-membered ring and maintaining a tertiary alcohol, there are 3 distinct isomers that fit these criteria.
A beta-lactam is a lactam with a four-membered ring structure - a structural element of many antibiotics, including penicillin.
sedoheptulose-diphosphate
Nicotine contains a pyridine ring, which is a nitrogen-containing aromatic ring, and a pyrrolidine ring, which is a five-membered nitrogen heterocycle. These functional groups contribute to the biological activity of nicotine in the central nervous system.
Ribose is a five-carbon sugar with a five-carbon ring structure found in RNA molecules. Sugars with six carbon atoms, like glucose and fructose, typically form six-membered rings in their structures.