1.10.4.3. Nucleic Acids-DNA and RNA: 5% of the Total Components in Mammalian Cell

• "Blueprints" of life
• Store information that the body needs to build proteins
• DNA (deoxyribonucleic acid)
• Stores information; delivers. 
• DNA & RNA (like proteins, carbohydrates, and lipids) are polymers--- long chains of smaller repeating units.  The repeating unit in nucleic acids is called a Nucleotide.
• Every nucleotide has the same basic structure as below:

• Comparison of DNA and RNA:

• So, DNA & RNA are alike in that they are both nucleic acids composed of nucleotides.
• Their differences lie in their functions and structure.
• The main structural differences are the number of strands in the molecule, the sugar structure, and one of the N-bases (thymine in DNA, uracil in RNA).

1.10.5. Chemical Reaction in Living Cell
Therefore, these four major types of macromolecules found in living cells—carbohydrates, lipids, proteins, and nucleic acids--are made of small, repeating subunits called monomers. The monomers are not always identical but they always have similar chemical structures. They are joined together by a series of chemical bond formed via the reactions called polymerisation to form large, complex molecules called polymers.

Macromolecular functions are directly related to their structures, shapes and to the chemical properties which is similar to their monomers. The way the monomers are arranged in the macromolecule determines its shape and function in the similar way that the arrangement of the letters in a word determine its sound and meaning.
Much of a cell's activities involve the proper organization and bonding of macromolecules and their inter/intra-molecular interactions with other macromolecules.  It is the job of DNA both directly and indirectly to coordinate and direct these activities. An understanding of the structure and functions of carbohydrates and lipids is not particularly key to the understanding of molecular family; however, they play a crucial role in maintaining the cell structure and functions.

1.10.5.1 Chemical Reaction in Living Cell: Dehydration Synthesis vs. Hydrolysis

The chemical process that connects the smaller subunits to form large organic macromolecules is called dehydration synthesis.  Hydrolysis is the process that breaks large organic macromolecules into their smaller subunits. It is the opposite of dehydration synthesis. In hydrolysis, water is added and the large compounds are split into small fragments. In living system, the process of hydrolysis is involved in digestion --- when food is broken down into nutrients.