Transcript lecture notes-biochemistry-4-Nucleic Acids

Nucleic Acids - RNA and DNA
is a complex, high-molecularweight biochemical macromolecule composed of
chains that convey genetic information.
The most common nucleic acids are
deoxyribonucleic acid (DNA) and ribonucleic
acid (RNA).
Nucleic acids are found in all living cells and
viruses.
Nucleotides
are the building blocks of DNA and
RNA.
• Serve as molecules to store energy and reducing power.
• The three major components in all nucleotides are
phosphoric acid, pentose (ribose and deoxyribose), and
a base (purine or purimidine).
• Two major purines present in nucleotides are adenine
(A) and guanine (G), and three major purimidines are
thymine (T), cytosine (C) and uracil (U).
Ribonucleotides
• Adenosine triphosphate (ATP) and guanosine
triphosphate (GTP), which are the major sources of
energy for cell work.
- The phosphate bonds in ATP and GTP are high-energy
bonds.
- The formation of phosphate bonds or their hydrolysis is
the primary means by which cellular energy is stored or
used.
• nicotinamide adenine dinucleotide (NAD) and
nicotinamide adenine dinucleotide phosphate (NADP).
The two most common carriers of reducing power
for biological oxidation-reduction reactions.
Deoxyribonucleic Acid (DNA)
Deoxyribonucleic acid (DNA) is formed by condensation
of
.
3
The nucleotides are linked together
between the 3’ and 5’ carbons’ successive
pentose rings by p
r
bonds
5
Deoxyribonucleic Acid (DNA)
- DNA is a very large threadlike macromolecule
(MW, 2X109 D in E. coli).
- DNA contains adenine (A) and guanine (G),
thymine (T) and cytosine (C).
- DNA molecules are two stranded and have a
double-helical three-dimensional structure.
DNA Double-helical Structure
Double Helical DNA Structure
The main features of double helical DNA structure are as
follows: .
- The phosphate and deoxyribose units are on the outer
surface, but the bases point toward the chain center. The
plane of the bases are perpendicular to the helix axis.
- The diameter of the helix is 2 nm, the helical structure
repeats after ten residues on each chain, at an interval of
3.4 nm.
- The two chains are held together by hydrogen bonding
between pairs of bases.
Adenine (A) , guanines (G) .
- The sequence of bases along a DNA strand is not
restricted in any way and carries genetic information,
and sugar and phosphate groups perform a structure
role.
DNA Replication
Regeneration of DNA from original DNA
segments.
http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter14/animations.html#
DNA Replication
- DNA helix unzips and forms two separate strands.
- Each strand will form a new double strands.
- The two resulting double strands are identical, and
each of them consists of one original and one
newly synthesized strand.
- This is called semiconservative replication.
- The base sequences of the new strand are
complementary to that of the parent strand.
Ribonucleic Acid (RNA)
• Ribonucleic acid (RNA) is formed by
condensation of
.
• RNA is a long, unbranched macromolecule and
may contain 70 to several thousand nucleotides.
RNA molecule is usually single stranded.
• RNA contains adenine (A), guanine (G), cytosine
(C) and uracial (U). A-U, G-C in some double
helical regions of t-RNA.
Classification of RNA
According to the function of RNA, it can be classified as:
•
RNA: (m-RNA) synthesized on chromosome
and carries genetic information to the ribosomes for
protein synthesis. It has short half-life.
•
RNA (t-RNA) is a relatively small and stable
molecule that carries a specific amino acid from the
cytoplasm to the site of protein synthesis on ribosomes.
•
RNA (r-RNA) is the major component of
ribosomes, constituting nearly 65%. r-RNA is responsible
for protein synthesis.
• Ribozymes are RNA molecules that have catalytic
properties.
Summary of Nucleic Acids
Nucleotides are basic units of nucleic acids DNA and RNA.
• Nucleotides include pentose, base and phosphoric acid.
• Bases include purine or pyrimidine.
• Two major purines present in nucleotides are adenine (A)
and guanine (G), and three major pyrimidines are thymine
(T), cytosine (C) and uracil (U).
• Ribonucleotides
- adenine triphosphate (ATP) stores energy.
- NAD and NADP are important carriers of reducing power.
Summary of Nucleic Acids
DNA
• DNA contains genetic information.
• DNA contains adenine (A) and guanine (G), and
thymine (T), and cytosine (C). A-T G-C
• DNA has a double helical structure.
• The bases in DNA carry the genetic information.
Summary of Nucleic Acids
RNA
• RNA functions as genetic information-carrying
intermediates in protein synthesis.
• It contains adenine (A) and guanine (G), and cytosine
(C) and uracil (U).
• m-RNA carries genetic information from DNA to the
ribosomes for protein synthesis.
• t-RNA transfers amino acid to the site of protein
synthesis
•
r-RNA is for protein synthesis.
Summary of Cell Construction
Biopolymers
subunit
bonds for
subunit
linkage
functions
Characteristic
three-D
structure
protein
Carbohydrates
(polysaccharides)
DNA
RNA
lipids