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NUCLEIC ACIDS

Are the largest and the most

complex organic molecules.

Friedrich Miescher who discovered

nucleic acids in !"

• NUCLIEC ACIDS are

macromolecules, found in all

cells, which precipitate in the

storage, transmission and

translation of genetic

information.

•  There are two tpes of nucleic

acids, the ri!ose nucleic acid

"#NA$ and the deo%ri!osenucleic acid "DNA$, which on

hdrolsis ield the sugar

ri!ose and deo%ri!ose

respecti&el.

Nucleic acids were #rst

isolated $rom the cellular

nucleus% hence the name&

Nucleic acids are

macromolecules% huge

pol'mers with molecularmasses o$ over (( million&

FUNC)I*N *F NUCLEIC ACIDS+

Functions o$ DNA

,deox'ri-onucleic acid.+

'DNA is a permanent storage

place for genetic information.

'DNA controls the snthesis of

#NA "ri!onucleic acid$.

'The se(uence of nitrogenous!ases in DNA determines the

protein de&elopment in new

cells.

 The function of the dou!le heli%

formation of DNA is to ensure

that no disorders occur. This is

!ecause the second identical

strand of DNA that runs anti'

parallel to the )rst is a !ac* up

in case of lost or destroed

genetic information. Ex . Down+s

Sndrome or Sic*le Cell Anemia.

Functions o$ /NA

,ri-onucleic acid.+

'#NA is snthesied ! DNA for

the transportation of genetic

information to the protein

!uilding apparatus in the cell.

'#NA also directs the snthesis

of new proteins using the

genetic information it has

transported.

'm#NA "messenger ri!onucleic

acid$ is used to transfer genetic

information through plasma

mem!ranes

• Nucleic acids "speci)call

DNA$ carr out a &ital role in the

human !od. In particular,

nucleic acids pla an essential

role in-Mitosis

,Meiosis

 

• 0roviding Energ' 1 Cellular

/espiration 

• Mitosis  During cell di&ision,

the chromosomes "or genetic

information$ contained inside

the nucleus of the parent cell is

duplicated. The two resulting

daughter cells ha&e identical

genetic information to the

parent cell. This is possi!le onl

through nucleic acid+s

remar*a!le a!ilit to create

identical copies of itself. It is

the onl molecule *nown to

ha&e this a!ilit. /itosis is

essential to life !ecause it

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0rimidine !aseCtosine, uracil or 

thmine

replaces damaged or dead cells,

repairs tissues, and allows the

!od to grow "in mass and sie$.

• Meiosis  Another use for

nucleic acid+s duplication a!ilitis meiosis. /eiosis is the

process in which se% cells are

created. 1ithout nucleic acids,

meiosis would !e impossi!le,

and so would reproduction.

•

• 0roviding Energ'  Nucleic

acids can !e used to create

energ in the form of AT0"adenosine triphosphate '

C23425N672808$. AT0 is

formed with the nitrogenous

!ases adenosine and ri!ose.

Composition o$ Nucleic Acids+

• Nucleic acids are su!stances

with high molecular weight

ranging from 2,9:5 to

8,333,333. The are made up of 

car!on, hdrogen, o%gen,

nitrogen and phosphorus.

• Nitrogen is from 26 to 25;

while phosphorus is from < to

23;. 7n hdrolsis with either

an enme or ! heating with

dilute acids or al*alies, nucleic

acids ields a group of

compound *nown as

nucleotides.

2inds o$ Nucleic Acids

DNA, deox'ri-onucleic acid.

found onl inside the nucleus

of the cell. Contains the

organism+s genetic information,

including instructions for how to

ma*e proteins. 

/NA, ri-onucleic acid.

found !oth inside and outside

of the nucleus. Directs the

!uilding of proteins.

3primaril' concerned with the

s'nthesis o$ protein&

  POLYPEPTIDES are the

!uilding !loc*s of nucleic acids.

DNA

• Deo%ri!onucleic acid is a

nucleic acid that contains the

genetic instructions used in the

de&elopment and functioning of

all *nown li&ing organisms. Themain role of DNA molecules is

the long'term storage of

information and DNA is often

compared to a set of !lueprints,

since it contains the instructions

needed to construct other

components of cells, such as

proteins and #NA molecules.

•  The DNA segments that carr

this genetic information are

called genes, !ut other DNA

se(uences ha&e structural

purposes, or are in&ol&ed in

regulating the use of this

genetic information.

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• Deo%ri!ose is present in the

nucleic acid found in the east

cell nuclei, while ri!ose is

contained in the nucleic acid

o!tained from pancreas.

 –  There are cases also were

!oth of nucleic acids are

found together. So that it

is now de)nitel

accepted that !oth the

ri!ose and deo%ri!ose

nucleic acids are found in

plants and animals= and

that while the

deo%ri!ose tpe is found

in the nucleic of the cells

"white$ the ri!ose tpe

predominate in the

ctoplasm

Some amount of DNA are also

housed in the cell+s

mitochondria, whose main

function is to generate the

energ needed for the cell

functioning, it couldn+t !e in the

cell wall, !ecause human cells

are !ound ! mem!rane and

lac* the cell walls that plants

ha&e.

 There are DNA &iruses, li*e

herpes !ut some of the most

pre&alent, li*e the common cold

or in>uena, as well as other

well'*nown &iruses li*e hepatitis

C and are #NA &iruses.

/NA

• #i!onucleic acid "#NA$ functions

in con&erting genetic

information from genes into the

amino acid se(uences of

proteins. The three uni&ersal

tpes of #NA include transfer

#NA "t#NA$, messenger #NA

"m#NA$, and ri!osomal #NA

"r#NA$. Messenger RNA acts to

carr genetic se(uenceinformation !etween DNA and

ri!osomes, directing protein

snthesis. Ribosomal RNA is a

ma?or component of the

ri!osome, and catales peptide

!ond formation.

•  Transfer #NA ser&es as the

carrier molecule for amino acids

to !e used in protein snthesis,

and is responsi!le for decoding

the m#NA. In addition, man

other classes of #NA are now

*nown.

• #i!onucleic acid is found onl in

plants while the

deo%ri!onucleic acid is

e%clusi&e of animal products

2inds o$ /NA

. Transfer #NA 23 t7 26;

  'small, a!out :3 nucleotides long.

  'transport amino acids to site of

protein snthesis.

 'e%hi!its e%tensi&e inter chain of

!onding represent ! clo&er leaf

structure.

9$ #i!osomal #NA @6 to :3;

  'se&eral *inds &aria!le in sie 'com!ines with proteins to form

ri!osomes, the site oh C47N

snthesis.

 ' molecules to !e (uite large.

8$ /essenger #NA '&aria!le sie"its

sie &aries with the sie of C47N$

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  'directs amino acids se(uence of

proteins

  ' e%tent of it !onding is &er little

' in most cells it constitutes not more

than 6; to 23; of the total cellular

#NA.

0roperties o$ Nucleic Acids+

• Nucleic acids are insolu!le in

alcohol, slightl solu!le in cold

water, !ut readil dissol&ed in

hot water and dilute al*alies,

forming al*ali salts. The are

precipitated ! 4CL and !

e%cess of acetic acid.

• Beulgen Test dierentiates the

DNA from #NA, if the

deo%ri!ose sugar is present, a

rd color is produced with the

de. #i!ose sugar do not e%hi!it

this reaction.

4'drol'sis o$ nucleic acids

gives nucleotide% which can -e

considered the units that ma5e

up the pol'mer& A nucleotideconsists o$ three parts+

& 4eteroc'clic -ase

  6& sugar

  7& phosphoric acids

Sugar

 The sugar in nucleotide, and so in

nucleic acids , is a 0ENT7SE. In #NA

and its nucleotide the sugar is #I7SE,

whereas in DNA and its nucleotide it is

DE7F#I7SE. The pre)% deo% '

means Gwithout o%genH .

Nucleotides can !e hdroled to ield

nucleosides and phosphoric acid.

4E)E/*C8CLIC 9ASES

0resent in nucleic acids are

di&ided into two tpes' 0U#INES

and 0F#I/IDINES. The two

0urines present !oth DNA and

#NA are adenine and guanine.

 The 0rimidines ctosine is

present in !oth DNA and #NA,

whereas thmine is found in

DNA onl and Uracil is presentin #NA onl.

)4E 08/IMIDINES

0rimidines is a si%'mem!ered

heterocclic ring containing two

nitrogen atom. Three important

deri&ati&es of 0rimidine found

in nucleic acids are

thmine"9,'dio%'6'

methlprimidine$, ctosine"9'o%''aminoprimidine$, and

Uracil"9,'dio%primidines$.

7ther important compound

containing 0rimidines are

thiamin "&itamin one$.

)4E 0U/INES

'The 0urines found in nucleic acids are

deri&ati&es of a su!stances, 0urine,

that does not occur naturall. As

indicated ! their structures, adenine

is 5'amino'purine and guanine is 9'

amino'5'o%purine.

7ther 0urine include caeine and

theophlline. Caeine is a stimulant

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for the central ner&ous sstem and

also a diuretic, and found in coee and

tea. Its chemical name is 2,8,@'

trimethl'9,5'dio%purine.

 Theophlline, 2,8'dimethl'9,5'

dio%purine, is found in tea and isused medicall as a diuretic and for

!ronchial asthma.Uric acid is the end

product of purine meta!olism.

DNA are &er long molecules

with speci)c se(uence of the for

principal !ases

Adenine,Thmine,Juanine,Cto

sine' A,T,J,C.

 The two chains of the heli% arecoiled to allow the proper

hdrogen !onding. The are

complementar in terms of

appropriate pairing, A to T and

C to J.

Nucleic acids and their derivatives

Are not dietar essentials.

 The can !e snthesie in &i&ofrom amino acids and other

su!stances.

 The in>uence the general

pattern of meta!olism "in

chromosomes, &iruses and

other cells$ and act as

ctoplasmic regulations of

protein snthesis.

Levels o$ structure in Nucleicacids

2. 0rimar structure of nucleic

acids is the order of !ases in the

polnucleotide se(uence.

9. Secondar structure is the 8'

dimensional conformation of the

!ac*!one.

8. Tertiar structure is speci)call

the super coiling of themolecule.

In the earl 2<63s, four

scientists, Kames

1atson andBrancis Cric* at

Cam!ridge Uni&ersit

and /aurice

1il*insand #osalind Bran*lin at

ings College, determined the

true structure

of DNA from data and 'rapictures of the molecule that

Bran*lin had ta*en. In 2<68,

1atson and Cric* pu!lished a

paper in the scienti)c

 ?ournalNature descri!ing this

research. 1atson, Cric*, 1il*ins

and Bran*lin had shown that not

onl is the DNA molecule

dou!le'stranded, !ut the two

strands wrap around each other

forming a coil, or heli%. The true

structure of the DNA molecule is

a dou!le heli%, as shown at

right.

 The dou!le'

stranded DNA molecule has the

uni(ue a!ilit that it can ma*e

e%act copies of itself, or self'

replicate. 1hen more DNA is

re(uired ! an organism "suchas during reproduction or cell

growth$ the hdrogen

!onds !etween

thenucleotide !ases !rea* and

the two single strands of DNA

separate. New complementar

!ases are !rought in ! the cell

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and paired up with each of the

two separate strands, thus

forming two new, identical,

dou!le'stranded DNA

molecules. This concept is

illustrated in the animation!elow.

Secondar' structure o$ DNA

' dou!le heli%

  'DNA consists of 9 polnucleotide

chains wrapped around each other to

form a heli%.

  'the sugar 07 !ac*!ones, run in

antiparallel directions on the 9

strands , lie on the outside of the

heli%.

  3pairs of !ases, one on each strands,

are held in alignment hdrogen !onds.

 The !ases pairs lie in a plane

perpendicular to the heli% a%is.

  3no twists in it other than the helica

twists.

)ertiar' structure o$ DNA +

3 super coiling

  ' further twisting M coiling of dou!le

heli%.

E%- pro*arotes and eu*arotes

/NA

/i-onucleic acid% or /NA% gets its

name $rom the sugar group in the

molecule:s -ac5-one 3 ri-ose&

Several important similarities and

di;erences exist -etween /NA

and DNA& Li5e DNA% /NA has a

sugar3phosphate -ac5-one

with nucleotide -ases attached toit& Li5e DNA% /NA contains the

-ases adenine ,A.% c'tosine ,C.%

and guanine ,<.= however% /NA

does not contain th'mine%

instead% /NA:s $ourth nucleotide

is the -ase uracil ,U.

Unli5e the dou-le3stranded

DNA molecule% /NA is a

single3stranded molecule&

/NA is the main genetic

material used in

the organisms called

viruses% and /NA is also

important in the production

o$ proteins in other living

organisms& /NA can move

around the cells o$ living

organisms and thus serves

as a sort o$ genetic

messenger% rela'ing thein$ormation stored in the

cell:s DNA out $rom

the nucleus to other parts o$ 

the cell where it is used to

help ma5e proteins&

DNA 9ASES

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DNA S)/UC)U/E

/NA S)UC)U/E

NUCLE*0/*)IENS

0roperties o$ Nucleoprotein+ 

• Nucleoproteins are fran*l

acidic and are solu!le in al*alies

with which the form salt. The

precipitated from their solutions

! acetic acid '' are redissol&ed

! dilute 4CL. The are not

coagulated ! '' !ut e%hi!it theprecipitation and color reactions

characteristic of protein

su!stances.

Importance o$ nucleoproteins+ 

•  Their importance lies in the

increasing e&idence that the

are closel associated with the

chromosomes of the cells.

•

In the !acteria cells, su!stancesha&e !een demonstrated, which

can transform one genetic tpe

of !acteria into another genetic

strain. The ha&e !een pro&en

to !e deo%ri!onucleic acid

MU)A)I*N

• /utations can in&ol&e large

sections of DNA

!ecoming duplicated, usuallthrough genetic

recom!ination. These

duplications are a ma?or source

of raw material for e&ol&ing new

genes, with tens to hundreds of

genes duplicated in animal

genomes e&er million

ears. /ost genes !elong to

larger families of

genes of shared ancestr. No&el

genes are produced ! se&eralmethods, commonl through

the duplication and mutation of

an ancestral gene, or !

recom!ining parts of dierent

genes to form new

com!inations with new

functions.

• nucleoprotein%  con>ugated

protein consisting of

a protein lin*ed to a nucleic

acid, either

DNA "deox'ri-onucleic acid$

or /NA "ri-onucleic acid$.

 The protein com!ined with DNA

is commonl either histone or

protamine= the resulting

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nucleoproteins are found in

chromosomes. /an &iruses are

little more

than organied collections of

deo%ri!onucleo proteins. Little

is *nown a!out the proteinslin*ed with #NA= unli*e

protamine and histone, the

appear to contain the amino

acid trptophan.

•  The term nucleo is deri&ed from

the earl erroneous !elief that

nucleoproteins occurs onl in

the nucleic cells.

Nucleotides and Nucleosides

• Nucleotides are the -uilding

-loc5s o$ all nucleic

acids& Nucleotides ha&e a

distincti&e structure composed

of three components co&alentl

!ound together-

• a nitrogen3containing

?-ase? ' either a primidine

"one ring$ or purine "two rings$

• a @3car-on sugar ' ri!ose or

deo%ri!ose

• a phosphate group

• )he com-ination o$ a -ase

and sugar is called

a nucleoside& Nucleotides also

e%ist in acti&ated formscontaining two or three

phosphates, called nucleotide

diphosphates or triphosphates.

If the sugar in a nucleotide is

deo%ri!ose, the nucleotide is

called a deo%nucleotide= if the

sugar is ri!ose, the term

ri!onucleotide is used. 

• )he structure o$ a

nucleotide is depicted-elow& The structure on the left

' deo%guanosine ' depicts the

!ase, sugar and phosphate

moieties. In comparison, the

structure on the right has an

e%tra hdro%l group on the 9

car!on of ri!ose, ma*ing it a

ri!onucleotide ' ri!oguanosine

or ?ust guanosine