Question

Identify the base and sugar in each of the following nucleosides: a. deoxythymidine b. adenosine c. cytidine d. deoxyguanosine

Short answer

a. deoxyribose, thymine; b. ribose, adenine; c. ribose, cytosine; d. deoxyribose, guanine.

Step-by-step solution

- Understanding Nucleosides

Nucleosides consist of a nitrogenous base attached to a five-carbon sugar (ribose or deoxyribose) but without a phosphate group. Identify whether the sugar is ribose (for ribonucleosides) or deoxyribose (for deoxyribonucleosides).

- Analyzing deoxythymidine

Deoxythymidine is a deoxyribonucleoside, meaning it contains deoxyribose. The nitrogenous base in deoxythymidine is thymine. Thus, the base is thymine, and the sugar is deoxyribose.

- Analyzing adenosine

Adenosine is a ribonucleoside, meaning it contains ribose. The nitrogenous base in adenosine is adenine. Thus, the base is adenine, and the sugar is ribose.

- Analyzing cytidine

Cytidine is a ribonucleoside, meaning it contains ribose. The nitrogenous base in cytidine is cytosine. Thus, the base is cytosine, and the sugar is ribose.

- Analyzing deoxyguanosine

Deoxyguanosine is a deoxyribonucleoside, meaning it contains deoxyribose. The nitrogenous base in deoxyguanosine is guanine. Thus, the base is guanine, and the sugar is deoxyribose.

Key concepts

nitrogenous bases

In the world of biology, nitrogenous bases play a crucial role. These compounds contain nitrogen and act as the building blocks of nucleotides, which in turn, are the foundations of nucleic acids like DNA and RNA. The primary nitrogenous bases are adenine (A), thymine (T), cytosine (C), guanine (G), and uracil (U). Each base has specific pairing rules essential for the storage and transmission of genetic information. For example, in DNA, adenine pairs with thymine and cytosine pairs with guanine. In RNA, thymine is replaced by uracil.

five-carbon sugar

A key component of nucleosides is the five-carbon sugar. This sugar can be either ribose or deoxyribose, determining whether the nucleoside forms part of RNA or DNA, respectively. Ribose is found in ribonucleic acid (RNA), while deoxyribose is in deoxyribonucleic acid (DNA). The primary difference between the two sugars is that ribose has one more oxygen atom than deoxyribose. These sugars provide the backbone to which nitrogenous bases attach, forming the structure of nucleosides and nucleotides.

ribonucleosides

Ribonucleosides are molecules consisting of a nitrogenous base attached to a ribose sugar without any phosphate group present. Examples of ribonucleosides include adenosine, cytidine, guanosine, and uridine. Understanding ribonucleosides is crucial as they are the building blocks of RNA. For instance, adenosine pairs adenine with ribose, and cytidine pairs cytosine with ribose. Ribonucleosides are integral to processes like protein synthesis and regulation of gene expression.

deoxyribonucleosides

Deoxyribonucleosides are similar to ribonucleosides but have a deoxyribose sugar instead of a ribose. This makes them essential components of DNA. Examples include deoxyadenosine, deoxycytidine, deoxyguanosine, and deoxythymidine. The absence of an oxygen molecule in deoxyribose gives DNA its stability, which is crucial for storing genetic information over long periods. Each deoxyribonucleoside pairs a nitrogenous base with a deoxyribose sugar, forming the skeleton of DNA strands.