The nucleic acids include the amazing DNA molecule. It is the source of constancy and variation among species, and is the foundation for the unity and diversity of all life on Earth.

Nucleic Acids Nucleic acids store and transmit hereditary information The amino acid sequence of a polypeptide is programmed by a unit of inheritance called a gene Genes are made of DNA, a nucleic acid Genes Are the units of inheritance Program the amino acid sequence of polypeptides Are made of specific nucleotide sequences on DNA

The Roles of Nucleic Acids There are two types of nucleic acids involved in inheritance and protein synthesis Deoxyribonucleic acid (DNA) Ribonucleic acid (RNA) DNA DNA –Stores information for the synthesis of specific proteins –Found in the nucleus of cells –Directs RNA synthesis (transcription) –Directs protein synthesis through RNA (translation) RNA RNA –Single stranded nucleic acid which carries the code for protein synthesis –Found in nucleus, and outside of nucleus in association with ribosomes

The Structure of Nucleic Acids Nucleic acids Exist as polymers called polynucleotides Each polynucleotide Each polynucleotide –Consists of monomers called nucleotides –Sugar + phosphate + nitrogen base 3’C 5’ end 5’C 3’C 5’C 3’ end OH O O O O Nucleotide monomers Nucleotide monomers –Are made up of nucleosides (sugar + base) and phosphate groups –The portion of a nucleotide without the phosphate group is called a nucleoside Nitrogenous bases Pyrimidines Cytosine (C) Thymine (T, in DNA)Uracil (U, in RNA) Purines Adenine (A)Guanine (G) Sugars Deoxyribose (in DNA) Ribose (in RNA) (c) Nucleoside components: sugars

Nucleotide Monomers Nucleoside = nitrogenous base + sugar There are two families of nitrogenous bases: Pyrimidines (cytosine, thymine, and uracil) have a single six-membered ring Purines (adenine and guanine) have a six-membered ring fused to a five-membered ring In DNA, the sugar is deoxyribose; in RNA, the sugar is ribose Cytosine Thymine Uracil Adenine Guanine DeoxyriboseRibose

Nucleotide Polymers Nucleotide polymers are linked together to build a polynucleotide Adjacent nucleotides are joined by covalent bonds that form between the –OH group on the 3 carbon of one nucleotide and the phosphate on the 5 carbon on the next These links create a backbone of sugar-phosphate units with nitrogenous bases as appendages The sequence of bases along a DNA or mRNA polymer is unique for each gene

DNA Double Helix P P P O O O P P P O O O TA G C When guanine and cytosine bond, they form triple hydrogen bonds H-bonds When thymine and adenine bond, a double hydrogen bond is formed

Antiparallel nature: Sometimes called complementary” sugar/phosphate backbone runs in opposite directions one strand runs 5’ to 3’, while the other runs 3’ to 5’; One DNA molecule includes many genes Remember, the nucleotides connect together at the hydroxyl group of the 5’ carbon sugar (at the 3’ end)

Scientists can use DNA and Proteins as Tape Measures of Evolution Molecular comparisons Help biologists sort out the evolutionary connections among species How similar are the sequences of nucleotides? The closer the sequence, the closer the relationship Remember, all life, from the simplest prokaryote to the most complex eukaryote, contains the same four nitrogenous bases. It is simply the sequence of base-pairs, and amount of DNA that differs from organism to organism!

Adenosine triphosphate is a common source of activation energy for metabolic reactions. ATP is essentially an RNA adenine (adenosine) nucleotide with two additional phosphate groups. The wavy lines between these two phosphate groups indicate high energy bonds. When that last bond is broken, and the ATP is converted to ADP (adenosine diphosphate), energy is released, and can be used to spur a reaction. Conversely, a new ATP molecule can be built by combining ADP and a phosphate through a process known as phosphorylation using energy obtained from glucose.