Proteins, Lipids, Carbohydrates, and Nucleic Acids Help

By — McGraw-Hill Professional
Updated on Aug 30, 2011

Introduction to Proteins, Lipids, Carbohydrates, and Nucleic Acids

The various groupings of covalently bonded carbon atoms form the skeleton or backbone of the four major types of chemical body-builders: proteins , lipids ( LIP -ids), carbohydrates ( kar -boh- HIGH-draytes ), and nucleic (new- KLEE -ik) acids .


A protein is a large organic molecule consisting of linked amino (ah- ME -noh) acids . An amino acid is characterized by the presence of a nitrogen-containing amino (NH 2 -) group of atoms. Structural proteins are the critical building-blocks found in most plant and animal tissues. Enzymes ( EN -zihms) are proteins that speed up various chemical reactions, without themselves being changed in the process. Every living cell contains thousands of structural proteins and enzymes.


A lipid is a group of “fats” ( lip ) and fat-like hydrocarbons that are not dissolvable in water. The main reason fats cannot dissolve in water is because they contain large numbers of uncharged C–C and C–H bonds, while water does not have bonds of this type. Many lipid molecules are created when too many calories are consumed. Various lipids also occur within the membranes of cells. Other members of the lipid family are really not fats, at all. This group includes the hormones , which act as chemical messengers.


Carbohydrates are literally “carbon–water” molecules, that is, their molecules can be considered to consist of equal numbers of carbon atoms and H 2 O molecules. Glucose, a very important carbohydrate, for instance, can have its molecular formula written as C 6 H 12 O 6 , or as C 6 (H 2 O) 6 – six carbon atoms with six water molecules. In actual fact, however, glucose has a closed ring structure, with no water molecules included.

Some of the carbohydrates, such as glucose, serve as the major sugars used for energy by many cells. In certain plants, carbohydrates can help build cell walls.

Nucleic Acids

The nucleic acids get their name from their occurrence within the “nucleus” of eukaryote cells. The nucleic acids include nitrogen-containing bases as their chief components. All of the living organisms contain two major types of nucleic acids – DNA and RNA. DNA is an abbreviation for deoxyribonucleic (de- ahk -see-righ-boh-noo- KLEE -ik) acid. RNA, on the other hand, is an abbreviation for ribonucleic ( righ -boh-noo- KLEE -ik) acid . DNA occurs as a twisted ladder or double helix, and it includes genes along its length. These genes serve as codes for the production of body proteins and other chemicals. Several types of RNA make copies of the code, so it can be translated into the actual production of body proteins.


Practice problems for these concepts can be found at:  Chemical Building Blocks Test

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