0.4 Bis2a 03.4 nucleic acids v1.2  (Page 42/20)

Nucleic acids

Nucleic acids carry the genetic blueprint of a cell and carry instructions for the functioning of the cell. In some instances, nucleic acids, primarily RNA, are also involved in catalysis and enzymatic activity. In such cases RNA-protein enzymes are often referred to as ribozymes and include such enzymes as RNaseP, the Ribosome, and the splicesome.

Dna and rna

The two main types of nucleic acids are deoxyribonucleic acid (DNA)    and ribonucleic acid (RNA)    . 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 and in the "nucleoid" in prokaryotes, that is bacteria and archaea, which is NOT enclosed in a membranous envelope. For a quick video (2 minutes) that goes over the differences of DNA and RNA click here .

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. DNA controls all of the cellular activities by turning the genes “on” or “off.”

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. This intermediary is the messenger RNA (mRNA)    . Other types of RNA—like rRNA, tRNA, and microRNA—are involved in protein synthesis and its regulation.

DNA and RNA are made up of monomers known as nucleotides . The nucleotides combine with each other to form a polynucleotide    , DNA or RNA. Each nucleotide is made up of three components: a nitrogenous base, a pentose (five-carbon) sugar, and a phosphate group ( [link] ). Each nitrogenous base in a nucleotide is attached to a sugar molecule, which is attached to one or more phosphate groups.