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7/25/2019 Nu Cleo Proteins
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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