Nucleic Acids

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Chapter: Anatomy and Physiology for Health Professionals: Levels of Organization : Chemical Basics of Life

Nucleic acids are large organic molecules (macro-molecules) that carry genetic information or form ­structures within cells.

Nucleic Acids

Nucleic acids are large organic molecules (macro-molecules) that carry genetic information or form ­structures within cells. They are composed of car-bon, hydrogen, oxygen, nitrogen, and phosphorus. Nucleic acids are actually the largest molecules in the body. Nucleic acids store and process information at the molecular level inside the cells. The two classes of nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Nucleic acids are found in allliving things, cells, and viruses. Individual strands of DNA and RNA have a similar structure (FIGURE 2-14).

Nucleotides are the structural units of nucleicacids. These complex units consist of a nitrogen-­ containing base, a pentose sugar, and a phosphate group. The nucleotide structure is based on five major types of nitrogen-containing bases:

Adenine (A): A large, two-ring base (purine)

Guanine (G): Also a purine

Cytosine(C): A smaller, single-ring base (pyrimidine)

Thymine (T): Also a pyrimidine

Uracil (U): Also a pyrimidine

The DNA in our cells determines our inherited characteristics, including hair color, eye color, and blood type. DNA affects all aspects of body structure and function. DNA molecules encode the information needed to build proteins. By directing structural pro-tein synthesis, DNA controls the shape and physical characteristics of the human body.

Several forms of RNA cooperate to manufacture specific proteins by using the information provided by DNA. Important structural differences distin-guish RNA from DNA. An RNA molecule consists of a single­ chain of nucleotides. Human cells have three types of RNA:

1.Messenger RNA (mRNA)

2.Transfer RNA (tRNA)

3.Ribosomal RNA (rRNA)

A DNA molecule consists of a pair of nucleotide chains (FIGURE 2-15A ). The two DNA strands twist around each other in a double helix that resembles a spiral staircase. TABLE 2-3 compares the characteristics of DNA and RNA.

1. List three types of RNA.

2. Distinguish between DNA and RNA.

3. What is the structure of nucleotides?

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