Chapter 6, Problem 44A

Summary Introduction

Introduction :

Carbon atoms join to form carbon molecules. Similarly, most cells have small carbon compounds that act as the building blocks for large molecules. Smaller organic molecules join together to form macromolecules or polymers. Polymers are formed by repeating units of nearly identical or identical compounds known as monomers joined by a series of covalent bonds. The biological macromolecules are divided into four major classes - carbohydrates, proteins, lipids and nucleic acids.

Answer to Problem 44A

Correct answer :

The correct answer is option (D) water.

Explanation of Solution

Explanation/justification for the correct answer :

Option (D) water. Nucleic acids are complex macromolecules that store and transmit genetic information. They are made of smaller repeating subunits called nucleotides. Nucleotides are composed of carbon, oxygen, nitrogen, phosphorus and hydrogen atoms. There are six major nucleotides, all having three units- a phosphate, a ribose sugar and nitrogenous base. Water is not a unit of a nucleotide. So, the correct answer is option (D).

Explanation for incorrect answer :

Option (A) a phosphate. Nucleotides are small units that join together to form nucleic acids. They are composed of carbon, oxygen, nitrogen, phosphorus and hydrogen atoms. There are six major nucleotides, all having three units- a phosphate, a ribose sugar and nitrogenous base. Thus, phosphate group is part of a nucleotide. So, this is an incorrect option.

Option (B) a base. Nucleotides are small units that join together to form nucleic acids. They are composed of carbon, oxygen, nitrogen, phosphorus and hydrogen atoms. There are six major nucleotides, all having three units- a phosphate, a ribose sugar and nitrogenous base. A nitrogen containing base is part of a nucleotide. So, this is an incorrect answer.

Option (C) a sugar. Nucleotides are composed of carbon, oxygen, nitrogen, phosphorus and hydrogen atoms. There are six major nucleotides, all having three units- a phosphate, a ribose sugar and nitrogenous base. Hence, this is an incorrect answer.