Transcript 02 DNA and RNA and protein synthesis

Introduction
 Nucleic acids are
macromolecules made up
of smaller nucleotide
subunits.
 They carry genetic
information, form specific
structures in a cell or carry
out specific roles in a cell.
 Found in all living things
and viruses.*
 The two most common are
deoxyribonucleic acid
(DNA) and ribonucleic
acid (RNA).
Structure
 Nucleotides consist of
 A nitrogenous base
 A pentose sugar
 A phosphate group*
DNA
 Used primarily for the
carrying of hereditary
information and the recipe
for making proteins.
 DNA contains four
different types of
nucleotides that differ in
their nitrogenous base
only.
 The four bases are:
Adenine, Guanine,
Cytosine and Thymine.
DNA
 The shape of DNA is a
double helix, where two
nucleotide strands run
anti-parallel to each
other.
 It looks like a twisted
ladder where the sugar
and phosphate groups
make up the sides and
the nitrogenous bases
make up the rungs.
DNA
 The nucleotides are held
together by two types of
bonds.
 Phosphodiester bonds link
the phosphate group of
one nucleotide to the sugar
of an adjacent nucleotide
along the side of the
double helix.
 The nitrogenous bases are
held together by hydrogen
bonds across a rung.
DNA
 In DNA, Adenine will
only bind with Thymine
and Guanine will only
bond with Cytosine
based on the number of
hydrogen bonds each
can form.
 A and T each form 2
while C and G each form
3.
RNA
 Unlike DNA, RNA is single
stranded and generally
much shorter in length.
 RNA uses nucleotides
Adenine, Cytosine and
Guanine, but instead of
Thymine, it uses another
pyrimidine, Uracil.
 There are three different
types of RNA. They all
play important roles in
protein synthesis.
mRNA
1) Messenger RNA decodes the DNA code (“protein
recipe”) and takes it from the nucleus to the ribosome.
tRNA
2) Transfer RNA brings
amino acids to the
ribosome to be
incorporated into the
newly forming
polypeptide chain.
rRNA
3) Ribosomal RNA is what makes up the ribosomes, where
proteins are made in the cell.
Other Important Nucleic Acids
1) Adenosine Triphosphate (ATP) which is the energy currency of
the cell.
2) NAD, FAD, GDP and NADP, which are high energy electron
carrying molecules used in cellular respiration or
photosynthesis.
Introduction
 Protein production relies on
complex interactions among
organelles.
 Protein synthesis is important
because nearly all cell processes
require proteins.
Ex: A spider produces proteins in
order to spin a web and humans
produce hemoglobin in order to
transport oxygen to all the cells
and take carbon dioxide away.
Protein Synthesis
 Protein synthesis refers to
making proteins. It occurs
in a 6 step process in all
cells:
1.
The DNA that codes for a
protein is copied onto a
similar molecule called
messenger RNA
(mRNA). This happens
in the nucleus and is
called transcription.
Protein Synthesis

Remember RNA uses
Uracil instead of
Thymine, so when
DNA has an Adenine
molecule, the RNA
molecule will have a
Uracil bound to it.
Protein Synthesis
2. The messenger RNA
carries the coded
message from the
nucleus to ribosomes
in the cytoplasm. It
exits the nucleus
through the nuclear
pore.
Protein Synthesis
3. A ribosome clamps onto the mRNA and the code for
protein (codons) begins to get translated into amino
acids, the building blocks of protein.
Protein Synthesis
4. Special molecules
called transfer RNA
(tRNA) bring the
amino acids the recipe
calls for to the
ribosome in the correct
sequence specified by
mRNA.
Protein Synthesis
5. Two tRNAs can be at the ribosome at one time.
When two are there, one will attach its amino acid
to the amino acid of the other one, creating a chain
of amino acids. Once this happens, that tRNA
leaves and the one with the chain moves to its place.
Protein Synthesis
6. Once the entire mRNA is read by the ribosome all the
parts will separate. The amino acid chain will then
fold into a functional protein. The others will wait for
another chance at translation.