3.3 Nucleic Acids: Information Molecules

Are polymers called polynucleotides Composed of monomers called nucleotides Each nucleotide consists of a nitrogenous base,

a pentose sugar, and a phosphate group

The portion of a nucleotide without the phosphate group is called a nucleoside

They perform specific functions within cells Store & transfer genetic information

There are 2 types of polynucleotides:

DNA (deoxyribonucleic acid) - Stores information for the synthesis of specific proteins - directs protein sysnthesis through RNA - stores hereditary information

RNA (Ribonucleic acid) - transcribes hereditary information to direct protein synthesis through mRNA. - mRNA carries the information needed for protein syntheis (intermediary between DNA and machinery for protein synthesis)

5' end

5'C

3'C

5'C

3'C

3' end

(a) Polynucleotide, or nucleic acid

(b) Nucleotide

Nucleoside

Nitrogenous base

3'C

5'C

Phosphate group Sugar

(pentose)

5′ end

Nucleoside

Nitrogenous base

Phosphate group Sugar

(pentose)

(b) Nucleotide

(a) Polynucleotide, or nucleic acid

3′ end

3′C

3′C

5′C

5′C

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

Nucleotide = nucleoside + phosphate group

Nucleoside = nitrogenous base + sugar There are two families of nitrogenous bases: ◦ Pyrimidines (cytosine, thymine, and uracil) have a single

six-membered ring (6C) ◦ Purines (adenine and guanine) have a six-membered

ring fused to a five-membered ring (9C)

• In DNA, the sugar is deoxyribose; in RNA, the sugar is ribose

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Structure of nucleotides • Each nucleotide consists of 3 components: a) Five carbon sugar (ribose (RNA) & deoxyribose (DNA) ) b) A phosphate group (-PO4) c) Organic nitrogenous base (nitrogen-containing base)

Ribose (in RNA) Deoxyribose (in DNA)

Sugars

(c) Nucleoside components: sugars

Structure of nucleotides

Two types/varieties of organic bases:

a)Purines: large double-ring molecules (9C) -Adenine (A) & guanine ( G) -Found in both DNA & RNA b) Pyrimidines: smaller single ring molecules (6C) -Cytosine (C) (DNA & RNA), thymine (T)

(DNA only) & uracil (U) (RNA only)

(c) Nucleoside components: nitrogenous bases

Purines

Guanine (G) Adenine (A)

Cytosine (C) Thymine (T, in DNA) Uracil (U, in RNA)

Nitrogenous bases Pyrimidines

- 4 types each in DNA and RNA

Polymerization of nucleotides

Condensation reaction

Phosphate group of one nucleotide binds to the hydroxyl group of adjacent nucleotide

Water is released

Phosphodiester bond Polynucleotide is a linear molecule called a strand.

Sugar-phosphate backbone – five-carbon sugars linked by

phosphodiester bonds –with organic bases protruding to one side of the backbone

Sequence of bases along a DNA or mRNA polymer is unique for each gene

Deoxyribonucleic acid (DNA)

Encoded genetic information - specifying the AAs sequence of proteins

One DNA molecule includes many genes

Double helix – twisted chains - antiparallel Each step - complementary base pairing – consisting of a base from one nucleotide joined by hydrogen bond to the base of the opposite nucleotide Base-pairing rules are rigid: Thymine (T)-Adenine (A) Cytosine (C) –Guanine (G)

Sugar-phosphate backbones

3' end

3' end

3' end

3' end

5' end

5' end

5' end

5' end

Base pair (joined by hydrogen bonding)

Old strands

New strands

Nucleotide about to be added to a new strand

Double-helix –two twisted chains - antiparallel

The DNA double helix and its replication

Base-pairing rules are rigid: Thymine (T)–Adenine (A) Cytosine (C)–Guanine (G) complementary to each other

Example of complementary base-pairing

Complementary base pairing during replication

DNA and Proteins as Tape Measures of Evolution

Evolution is the study of the biology of all species on the planet Earth and how the species have developed through time.

The linear sequences of nucleotides in DNA molecules are passed from parents to offspring

Two closely related species are more similar in DNA than are more distantly related species

Molecular biology can be used to assess evolutionary kinship Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

• The genetic information stored in DNA must be translated from the language of nucleic acids to the protein language.

• Translation is a term used to describe protein

biosynthesis. • RNA synthesis is the process of copying DNA

nucleotide sequence information into RNA sequence information.

• Allows genetic information to be translated through

the entire organism.

Ribonucleic acid (RNA) Polymer of nucleotides Contain ribose sugar Single-stranded molecules Encode protein-building

instructions from DNA Act as a messenger to translate the code into

proteins Three types a) messenger RNA (mRNA) b) transfer RNA (tRNA) c) ribosomal RNA (rRNA)

Comparison between DNA & RNA

DNA RNA

Sugar deoxyribose ribose

Nitrogenous bases adenine, guanine, thymine & cytosine

adenine, guanine, uracil & cytosine

Strands double-stranded with base pairing

single-stranded

Helix yes no

Location nucleus nucleus & cytoplasm

Adenosine Triphosphate (ATP) Energy currency of the cell Adenine – key component of ATP Also occur in the molecules of nicotinamide adenine

dinucleotide (NAD+) & flavin adenine dinucleotide (FAD)

NAD+ & FAD carry electrons used to make ATP

Last 2 phosphates are unstable

Energy functions of ATP

Synthesis of macromolecules

Muscle contraction

Metabolic and cellular driver

Nervous system functioning

Monomers or Components

Polymer or Larger molecules

Types of Linkage

Sugars Monosaccharides Polysaccharides Glycosidic linkages

Nucleic Acids Nucleotides Polynucleotides Phosphodiester linkages

Proteins Amino acids Polypeptides Peptide bonds

Lipids Fatty acids Triacylglycerols Ester Linkages

Characteristics of the different polymers