They carry the genetic blueprint of a cell and carry instructions for the functioning of the cell. DNA is the genetic material found in all living organisms, ranging from single-celled bacteria to multicellular mammals. It is found in the nucleus of eukaryotes and in the organelles, chloroplasts, and mitochondria. In prokaryotes, the DNA is not enclosed in a membranous envelope. The entire genetic content of a cell is known as its genome, and the study of genomes is genomics.
In eukaryotic cells but not in prokaryotes, DNA forms a complex with histone proteins to form chromatin, the substance of eukaryotic chromosomes. A chromosome may contain tens of thousands of genes. Many genes contain the information to make protein products; other genes code for RNA products. The other type of nucleic acid, RNA, is mostly involved in protein synthesis. The DNA molecules never leave the nucleus but instead use an intermediary to communicate with the rest of the cell.
Each nucleotide is made up of three components: a nitrogenous base, a pentose five-carbon sugar, and a phosphate group Figure 1. Each nitrogenous base in a nucleotide is attached to a sugar molecule, which is attached to one or more phosphate groups.
Figure 1. A nucleotide is made up of three components: a nitrogenous base, a pentose sugar, and one or more phosphate groups. Bases can be divided into two categories: purines and pyrimidines. Purines have a double ring structure, and pyrimidines have a single ring. The nitrogenous bases, important components of nucleotides, are organic molecules and are so named because they contain carbon and nitrogen.
This article has been posted to your Facebook page via Scitable LearnCast. Change LearnCast Settings. Scitable Chat. Register Sign In. Deoxyribonucleic acid DNA encodes the information the cell needs to make proteins. A related type of nucleic acid, called ribonucleic acid RNA , comes in different molecular forms that participate in protein synthesis. So they're actually made of polymers of strings of repeating units, and the two most famous of the nucleic acids, that you've heard about, are DNA and RNA.
And nucleic acids in the cell act to actually store information. The monomers combine with each other using covalent bonds to form larger molecules known as polymers.
In doing so, monomers release water molecules as byproducts. Figure 1. In the dehydration synthesis reaction depicted above, two molecules of glucose are linked together to form the disaccharide maltose. In the process, a water molecule is formed. In a dehydration synthesis reaction Figure 1 , the hydrogen of one monomer combines with the hydroxyl group of another monomer, releasing a molecule of water. At the same time, the monomers share electrons and form covalent bonds.
As additional monomers join, this chain of repeating monomers forms a polymer. Different types of monomers can combine in many configurations, giving rise to a diverse group of macromolecules. Even one kind of monomer can combine in a variety of ways to form several different polymers: for example, glucose monomers are the constituents of starch, glycogen, and cellulose.
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