Biology 107Biology 107

Macromolecules IIIMacromolecules III

September 11, 2002September 11, 2002

Protein “Partners” (Chaperones) Influence Folding

Functions of Functions of Nucleic AcidsNucleic Acids

Information coding, Information coding, storage, and transferstorage, and transfer

Synthesis of other nucleic Synthesis of other nucleic acids or proteinsacids or proteins

Central DogmaCentral Dogma

DNADNA

↓↓

RNARNA

↓↓

ProteinProtein

Structure of Nucleotides

Structure of Structure of NucleotidesNucleotides

Pentose sugarPentose sugar

Phosphate groupPhosphate group

Nitrogenous baseNitrogenous base

Nitrogenous BasesNitrogenous Bases

DNA Is Normally Double-Stranded

Each strand has polarity (5’ Each strand has polarity (5’ and 3’ ends).and 3’ ends).

In double-stranded DNA In double-stranded DNA each strand is oriented each strand is oriented “anti-parallel” to the other “anti-parallel” to the other strand.strand.

The strands are normally The strands are normally held together by hydrogen held together by hydrogen bonds.bonds.

The optimal hydrogen The optimal hydrogen bonding is when A bonds bonding is when A bonds with T and G bonds with C.with T and G bonds with C.

Base Pairing in DNABase Pairing in DNA

G/C pairs have G/C pairs have three hydrogen three hydrogen bondsbonds

A/T pairs have A/T pairs have two hydrogen two hydrogen bondsbonds

ATP Is a Nucleotide

ATP Structure and HydrolysisATP Structure and Hydrolysis

Macromolecules IIIMacromolecules III

Student Objectives:Student Objectives: As a result of this lecture and the assigned As a result of this lecture and the assigned reading, you should understand the following:reading, you should understand the following:

1.1. Nucleic Acids are polymers of nucleotides. There are two types of Nucleic Acids are polymers of nucleotides. There are two types of nucleic acids: deoxyribonucleic acid (DNA) and ribonucleic acid nucleic acids: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).(RNA).

2.2. Nucleic acids function in information coding, storage and transfer. Nucleic acids function in information coding, storage and transfer. DNA does not directly control protein synthesis, instead it works DNA does not directly control protein synthesis, instead it works through intermediates, RNA molecules.through intermediates, RNA molecules.

Macromolecules IIIMacromolecules III3.3. Each nucleotide monomer has three (3) parts: Each nucleotide monomer has three (3) parts:

five carbon sugarfive carbon sugar

phosphate groupphosphate group

nitrogenous basenitrogenous base

Nucleic acids contain one of two 5-carbon sugars, either Nucleic acids contain one of two 5-carbon sugars, either deoxyribose (in DNA) or ribose (in RNA). Linked to the one end deoxyribose (in DNA) or ribose (in RNA). Linked to the one end of the sugar is a phosphate group, and linked to the other end of of the sugar is a phosphate group, and linked to the other end of the pentose is one of the nitrogenous bases. DNA has the the pentose is one of the nitrogenous bases. DNA has the nitrogenous bases nitrogenous bases adenineadenine ( (AA), ), guanineguanine ( (GG),), thymine thymine ( (TT), and ), and cytosinecytosine ( (CC). RNA has A, G, C and ). RNA has A, G, C and uraciluracil ( (UU) (instead of thymine).) (instead of thymine).

Macromolecules IIIMacromolecules III4.4. A nucleic acid polymer, a polynucleotide, forms from monomers A nucleic acid polymer, a polynucleotide, forms from monomers

covalently linked by dehydration synthesis. The phosphate group covalently linked by dehydration synthesis. The phosphate group of one nucleotide bonds to the sugar of the next nucleotide, with of one nucleotide bonds to the sugar of the next nucleotide, with the result a repeating sugar-phosphate backbone. the result a repeating sugar-phosphate backbone.

5.5. RNA is normally a single polynucleotide strand, while DNA is a RNA is normally a single polynucleotide strand, while DNA is a double-stranded molecule. double-stranded molecule.

6.6. Nucleic acids form complementary base pairs stabilized by Nucleic acids form complementary base pairs stabilized by hydrogen bonds, with guanine pairing with cytosine and adenine hydrogen bonds, with guanine pairing with cytosine and adenine pairing with thymine or uracil.pairing with thymine or uracil.