Chapter 6, Problem 2STP

Summary Introduction

Introduction:

Carbon atoms can be joined to form carbon molecules. Similarly, most cells store small carbon compounds that serve as building blocks for large molecules. Macromolecules are large molecules that are formed by joining smaller organic molecules together. These large molecules are also called polymers. Polymers are molecules made from repeating units of identical or nearly identical compounds called monomers that are linked together by a series of covalent bonds. Biological macromolecules are organized into four major categories: carbohydrates, lipids, nucleic acids, and proteins.

Answer to Problem 2STP

Correct answer :

The correct answer is option (D) a protein.

Explanation of Solution

Explanation/justification for the correct answer :

Option (D) a protein. A protein is a compound made of small carbon compounds called amino acids. Proteins have four levels of structure. The number of amino acids chain and the order in which the amino acids are joined is the primary structure, after forming primary structure, it folds into a three-dimensional shape and forms the secondary structure which contain two basic structures, the helix and the pleat, many proteins form globular and forms the tertiary structure. Some proteins form a fourth level of structure by combining with other proteins. Therefore, the given structure is the protein which is the folded structure. So, the correct answer is option (D).

Explanation for incorrect answer :

Option (A) a carbohydrate. Compounds composed of carbon, hydrogen, and oxygen in a ratio of one oxygen and two hydrogen atoms for each carbon atom are called carbohydrate. Monosaccharides joined together to form a disaccharide which serve as an energy source. Longer carbohydrate molecules are called polysaccharides. Therefore, the given image cannot be a carbohydrate. So, this is an incorrect option.

Option (B) a lipid. Lipids are molecules made mostly of carbon and hydrogen that make up the fats, oils, and waxes. Based on the presence of bonds, lipids can be classified as saturated and unsaturated fats. Therefore, the given image cannot be a lipid. So, this is an incorrect answer.

Option (C) a nucleotide. Nucleic acids are made of smaller repeating subunits called nucleotides. In DNA and RNA, the sugar of one nucleotide bonds to the phosphate of another nucleotide. A nucleotide contains phosphate group. Therefore, the given image cannot be nucleotide. So, this is an incorrect answer.