1 minute read
Nucleic Acids
Simple carbohydrates are called monosaccharides and include glucose, fructose, and galactose. Disaccharides include lactose and sucrose. Figure 81 shows the basic sugars seen as monosaccharides or disaccharides in nature:
NUCLEIC ACIDS
Advertisement
Figure 81.
Nucleic acids are the main genetic material molecules in living things. There are two types: DNA and RNA. DNA is a long chain of unique nucleotides, which are the subunits of DNA and RNA. Nucleotides can be broken down into a pentose (5-carbon) sugar, phosphoric acid, and a nitrogenous base. Figure 82 shows what the nucleotides look like:
Figure 82.
The DNA of a typical mammal cell has about 30 billion nucleotides (per cell). The main differences between DNA and RNA include two things: 1) the pentose sugar in RNA is ribose when the pentose sugar in DNA is deoxyribose; and 2) there are a couple of changes in the bases with the thymine base exchanged for uracil in RNA. The bases are collectively referred to as pyrimidines or purines. Figure 83 shows the purines and pyrimidines in DNA and RNA:
Figure 83.
There is a bond between the C1’ of the pentose sugar and the N1 of the pyrimidine base or the N9 of the purine base that connects the molecules together (with the loss of water in the equation). The bases have an ability to connect through hydrogen bonding with each other in the double helical shape that makes up DNA. In this structure Adenine always connects with Thymine in DNA, while Guanine always connects with Cytosine in DNA. Uracil would bind with Adenine in double-stranded RNA; however, RNA is not often seen double stranded except in viruses.
You should know that, aside from being the monomer units of RNA and DNA, nucleotides have other significant properties. Adenosine triphosphate and adenosine diphosphate are ATP and ADP, respectively, which are highly important energy molecules in physiology. Other important energy molecules and coenzymes include FAD (flavin adenine dinucleotide) and NAD+ (nicotinamide adenine dinucleotide). Figure 84 shows what ATP looks like:
