They are compounds that have carbon, hydrogen and oxygen. There are 3 forms of carbohydrates. First are the monosaccharides which are simple sugars. They have simple structures in the ration of 1:2:1. They usually contain 5-6 atoms of carbon arranged in a 5-6 member ring. Oligosaccharides are monosaccharides which are combined in short strings that are linked together through dehydration synthesis. Sucrose is one of the oligosaccharides. It is a disaccharide since it consists of simply two monosaccharides. The last form are the polysaccharides which are straight or branched chains of monosaccharides joined together. Polysaccharides store energy. In animals, the storage polysaccharide is glycogen while in plants, it is starch Johnson 37-38() Lipids

Lipids are insoluble organic molecules. There are three subclasses. First are the triglycerides which are neutral fats synthesized from one glycerol molecule and three fatty acids. Fatty acids on the other hand are chains of hydrocarbons with about 16-18 carbons which end in a carboxyl group (COOH). Triglycerides are stored in adipose or fat tissue and in the body, they are an important source of energy for storage. The second group is the phospholipids which are the primary component in the structure of cell membranes. Phospholipids have one molecule of glycerol but only two fatty acids. Steroids are the last group. They are composed of four rings and a backbone of 3 six-membered rings of carbon and 1 five-membered carbon ring. A good example of steroids is cholesterol Johnson 39-40()

Proteins

Proteins are long strings of amino acids. All proteins in the human body consist of about 20 different amino acids. Each of these amino acids has an NH3 (amino) group on one of its ends and a carboxyl group on the other end. They also have a C-H group in the middle and a group that is represented by R. Johnson 40()

The function of each protein depends on its own structure. Proteins can be divided into four structure levels. Primary structure is represented by the sequence of amino acids. Secondary structure is described by the orientation in space of the chain of amino acids e.g. A helix or beta shape. Tertiary structure is how the...

Quaternary structure is the number of chains of polypeptides that make up the protein itself Johnson 42()
There are thousands of proteins in the human body. Some are for structural support, other are enzymes which regulate the rate of biochemical reactions in the body, and others are part of the cell membrane. Others are also involved in contraction of muscles. Proteins can easily be denatured by high temperatures or change in the level of pH Johnson 42()

Nucleic acids

Nucleic acids are stores of genetic information. They are two, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). DNA is the genetic material in all living things and it directs what the cell does. It also contains the instructions for the production of RNA. RNA on the other hand, contains the instructions for production of proteins. RNA also serves as the genetic material in some viruses Johnson 44()

Both DNA and RNA are composed of nucleotides which have a 5-carbon sugar, a double or single ringed structure with nitrogen and lastly, a phosphate groups. There are only four DNA and four RNA nucleotides that are present Johnson 44()

The structure of RNA is similar to that of DNA. However, there are some few exceptions. First is that the sugar in the nucleotides is ribose and not deoxyribose. Secondly, RNA is single-stranded and is shorter than DNA. RNA has only one of its four nitrogen-containing base molecules being different Johnson 45()

ATP

Adenosine triphosphate is the source of energy. It consists of a base of adenine, 4-carbon sugar ribose and 3 phosphate groups. When ATP is broken down, it produces adenosine diphosphate (ADP), an inorganic phosphate and releasing energy in the process. ATP is then replenished by energy that is in the food that is eaten or can also come from glycogen or fats stored in the body Johnson 46()

Works cited

Hunter, G.S. Let's Review: Biology, the Living Environment. Hauppauge, New York: Barron's Educational Series, 2008. Print.

Johnson, M.D. Human Biology: Concepts and Current Issues. San Francisco: Benjamin-Cummings Publishing Company, 2011. Print.