Nucleotide

Definition

A nucleotide is the basic building block of nucleic acids, such as DNA and RNA, consisting of three components: a phosphate group, a five-carbon sugar, and a nitrogenous base. These components play a crucial role in the structure and function of nucleic acids, allowing them to store genetic information and participate in protein synthesis. Nucleotides link together through phosphodiester bonds to form long chains, which are essential for the overall structure of DNA and RNA.

5 Must Know Facts For Your Next Test

1. Nucleotides can be classified into two categories: purines (adenine and guanine) and pyrimidines (cytosine, thymine, and uracil).
2. The sequence of nucleotides in DNA determines the genetic code and instructions for building proteins.
3. ATP (adenosine triphosphate), a special nucleotide, serves as the primary energy currency of the cell.
4. Nucleotides are linked by phosphodiester bonds between the phosphate group of one nucleotide and the sugar of another, forming the backbone of nucleic acid strands.
5. In addition to forming DNA and RNA, nucleotides are involved in cellular signaling and metabolism through molecules like cyclic AMP.

Review Questions

• How do nucleotides contribute to the overall structure of DNA?
  • Nucleotides contribute to the structure of DNA by linking together through phosphodiester bonds to form long chains. Each nucleotide consists of a phosphate group, a sugar molecule, and a nitrogenous base. The sequence of these bases along the DNA strand encodes genetic information, while the sugar-phosphate backbone provides structural integrity. The complementary pairing of nitrogenous bases between two DNA strands also creates the characteristic double helix structure.
• In what ways do purines and pyrimidines differ in their roles as nucleotides in nucleic acids?
  • Purines, which include adenine and guanine, have a double-ring structure and are larger than pyrimidines. Pyrimidines include cytosine, thymine (in DNA), and uracil (in RNA), featuring a single-ring structure. The difference in structure influences their pairing during DNA replication and transcription. Purines always pair with pyrimidines; specifically, adenine pairs with thymine (or uracil) and guanine pairs with cytosine. This complementary base pairing is crucial for maintaining the stability and integrity of the genetic code.
• Evaluate the significance of ATP as a nucleotide beyond its role in forming nucleic acids.
  • ATP is significant beyond being just a nucleotide that forms RNA because it serves as the primary energy currency in all living cells. It consists of adenine (a purine), ribose sugar, and three phosphate groups. The high-energy bonds between these phosphate groups allow ATP to release energy when hydrolyzed into ADP (adenosine diphosphate) and inorganic phosphate. This energy is utilized for various cellular processes such as muscle contraction, active transport across cell membranes, and biochemical synthesis reactions, making ATP vital for cellular function.

Related terms

DNA: Deoxyribonucleic acid, the molecule that carries genetic information in living organisms, composed of two strands that form a double helix.

RNA: Ribonucleic acid, a nucleic acid that plays a role in coding, decoding, regulation, and expression of genes, usually single-stranded.

base pairing: The specific hydrogen bonding between nitrogenous bases in nucleic acids; adenine pairs with thymine (or uracil in RNA) and cytosine pairs with guanine.