A Level Biology Practice Exam

Disable ads (and more) with a membership for a one time $2.99 payment

Prepare effectively for your A Level Biology Exam with our engaging quizzes and comprehensive resources. Test your knowledge and gain confidence with every practice question and detailed explanation. Get ready to excel in your exam!

Start Multiple Choice Practice Test
Start Flash Cards

Each practice test/flash card set has 50 randomly selected questions from a bank of over 500. You'll get a new set of questions each time!

Practice this question and more.

Purines are characterized as what kind of nitrogenous bases?

  1. Single-ringed

  2. Double-ringed

  3. Triple-ringed

  4. Quadruple-ringed

The correct answer is: Double-ringed

Purines are characterized as double-ringed nitrogenous bases. This structural feature is important because it distinguishes purines from pyrimidines, which have a single-ring structure. In the context of nucleic acids, purines include adenine (A) and guanine (G), both of which play critical roles in the formation of DNA and RNA. Their double-ring structure allows them to pair effectively with the single-ringed pyrimidines (cytosine, thymine, and uracil) during the processes of DNA replication and transcription, contributing to the stability and functionality of nucleic acid structures.

More Questions Like This