lecture 12 - nucleosides, nucleotides, DNA, RNA

what are nucleic acids

• large biomolecules that are essential in our bodies

• building blocks of DNA and RNA

• store, carry, translate genetic information

what do nucleic acids function as

• energy storage molecules (atp)

• signaling molecules

• redox coenzymes (NAD+/NADH)

structure of nucleic acids

• nitrogenous bases

• pentose sugars (5 carbon sugars)

• phosphate groups

nucleotides

base + sugar + phosphate

nucleosides

base + sugar (no phosphate)

nitrogenous bases

• purines (2 rings) - adenine (A), guanine (G)

• pyrimidines (1 ring) - cytosine (C), thymine (T), uracil (U)

  • DNA: AGCT

  • RNA: AGCU

  • ribonucleotides & RNA do NOT contain thymidine

• pyrimidines are NOT components of ATP or GTP

sugars in nucleic acids

• DNA sugar - deoxyribose (missing one hydroxyl group on 2’ carbon)

• RNA sugar - ribose (has hydroxyl group o0n 2’ carbon)

• in deoxynucleotides - phosphate groups attach to 3’ and 5’ hydroxyls

• DNA contains both deoxyribose and thymine

phosphate bonds & energy

• phosphate link sugars and bases n together

• phosphoanhydride bonds store and transfer energy

• energy released drives many cellular reactions

example of phosphate bonds & energy

ATP

what does ATP contain

• two phosphoanhydride and one phosphoester linkage

• hydrolysis of ATP → ADP + Pi releases 7.3 kcal/mol

what are the functions of nucleotides

• building blocks for DNA & RNA synthesis

• acts as energy carriers (ATP, GTP)

• function in cell signaling (cAMP, cGMP)

• serve as coenzymes in metabolism (NAD+, FAD, CoA)

• do NOT serve as membrane

what is the structure of DNA

• AT, CG base pairings

• stabilized by aromatic stacking between bases

• phosphate groups form phosphodiester bonds linking 3’ and 5’ carbons of sugars

• each base is NOT covalently linked to just one phosphate

• contains deoxyribose, cytosine, phosphate

what is the structure of RNA

• ribonucleic acid

• single stranded

• converts DNA information into proteins

• less stable than DNA

• base pairings - AU & CG

• contains ribose sugar

what is DNA replication

• semi conservative

• meselson stahl experiment

• each new DNA molecule has one parental strand and one new strand

• for two strands to hybridize, they must have complementary base pairs

what are the bonds in nucleic acid

phosphodiester bonds connect nucleotides between the 3’ and 5’ carbons

• two mono saccharides are linked by phosphodiester bonds

• backbone - sugar phosphate sugar phosphate

• bases project inward for pairing

what does FMN not contain

adenine

what are nucleotides composed of

organic bases, pentose sugars, phosphate

what are the main elements in the double helix

deoxyribose, cytosine, phosphate

when NAD+ turns into NADH, what does it gain

2 electrons