OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What components make up a nucleotide?

1. Base, enzyme, and amino acid

2. Five-sided sugar, phosphate group, and nitrogenous base

3. DNA, RNA, and protein

4. Carbon, hydrogen, and oxygen

The correct answer is: Five-sided sugar, phosphate group, and nitrogenous base

A nucleotide is a fundamental building block of nucleic acids, such as DNA and RNA. Each nucleotide is composed of three primary components: a five-sided sugar (specifically ribose in RNA and deoxyribose in DNA), a phosphate group, and a nitrogenous base. The five-sided sugar provides the structural framework of the nucleotide, allowing the attachment of the phosphate group and the nitrogenous base. The phosphate group links nucleotides together into long chains, forming the backbone of DNA or RNA, while the nitrogenous base encodes genetic information by pairing with complementary bases in the double helix structure of DNA. This structure is crucial for the functions of nucleic acids, including the storage and transmission of genetic information, as well as the synthesis of proteins through processes like transcription and translation.