Nucleotides and Nucleic Acids DNA and RNA

Lesson Learning Outcomes Upon completion of this lecture, students should be able to: understand the properties of nucleotides and nucleic acids recognize DNA and RNA

Essential Question What are the structures of the nucleotides? How are nucleotides joined together to form nucleic acids? How is information stored in nucleic acids? What are the biological functions of nucleotides and nucleic acids?

Level of structure in nucleic acids In proteins – primary, secondary, tertiary and quaternary Nucleic acids are viewed is the same way Primary structure: order of bases in polynucleotide Secondary structure: 3D conformation of the backbone Tertiary structure: supercoiling of the molecule

What are nucleic acids? Nucleic acids are large biological molecules, essential for all known forms of life.  Nucleic acids, which include DNA (deoxyribonucleic acid) and RNA (ribonucleic acid), are made from monomers known as nucleotides linked in a chain through phosphodiester bonds. In biological systems, they serves as information-carrying molecules or, in the case of some RNA molecules are catalysts.

What are nucleotides? Nucleotides are organic molecules that serve as the monomers, or subunits, of nucleic acids like DNA and RNA. The building blocks of nucleic acids Nucleotides are composed of a nitrogenous base, a five-carbon sugar (ribose or deoxyribose), and at least one phosphate group.

What is the Structure and Chemistry of Nitrogenous Bases? Pyrimidines Cytosine (DNA, RNA) Uracil (RNA) Thymine (DNA) Purines Adenine (DNA, RNA) Guanine (DNA, RNA)

DNA and RNA

Why is DNA 2'-deoxy and RNA is not? DNA & RNA Differences? Why is DNA 2'-deoxy and RNA is not? Vicinal -OH groups (2' and 3') in RNA make it more susceptible to hydrolysis DNA, lacking 2'-OH is more stable This makes sense - the genetic material must be more stable RNA is designed to be used and then broken down

What Are the Different Classes of Nucleic Acids? DNA - one type, one purpose RNA - 3 (or 4) types, 3 (or 4) purposes ribosomal RNA - the basis of structure and function of ribosomes messenger RNA - carries the message transfer RNA - carries the amino acids

Hydrolysis of Nucleic Acids RNA is resistant to dilute acid RNA is hydrolyzed by dilute base DNA is depurinated by dilute acid DNA is not susceptible to base

Functions of Nucleotides Nucleoside 5'-triphosphates are carriers of energy Bases serve as recognition units Cyclic nucleotides are signal molecules and regulators of cellular metabolism and reproduction ATP is central to energy metabolism GTP drives protein synthesis CTP drives lipid synthesis UTP drives carbohydrate metabolism

How does nucleotide forms nucleic acids? Nucleotides join together through phosphodiester linkages between the 5' and 3' carbon atoms to form nucleic acids. The 3' -OH of the sugar group forms a bond with one of the negatively charged oxygen of the phosphate group attached to the 5' carbon of another sugar. When many of these nucleotide subunits combine, the result is the large single-stranded polynucleotide or nucleic acid, DNA 

Nucleic acid polymers Polymers linked 3' to 5' by phosphodiester bridges Ribonucleic acid and deoxyribonucleic acid Know the shorthand notations Sequence is always read 5' to 3' Eg: 5’-CTTAGATACGTTGCCAGG-3’ In terms of genetic information, this corresponds to "N to C" in proteins

The DNA Double Helix Stabilized by hydrogen bonds! "Base pairs" arise from hydrogen bonds Erwin Chargaff had the pairing data, but didn't understand its implications Rosalind Franklin's X-ray fiber diffraction data was crucial Francis Crick knew it was a helix James Watson figured out the H bonds

Structure of DNA Double helix – James Watson and Francis Crick (1953)

End of lecture today. Please read up Campbell pg. 215-231