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Protein synthesis animation

here is a cell the basic unit of all

living tissue in most human cells there

is a structure called the nucleus the

nucleus contains the genome in humans

the genome is split between 23 pairs of

chromosomes each chromosome contains a

long strand of DNA tightly packaged

around proteins called histones within

the DNA are sections called genes these

genes contain the instructions for

making proteins when a gene is switched

on an enzyme called RNA polymerase

attaches to the start of the gene it

moves along the DNA making a strand of

messenger RNA out of free bases in the

nucleus the DNA code determines the

order in which the free bases are added

to the messenger RNA this process is

called transcription

before the messenger RNA can be used as

a template for the production of

proteins it needs to be processed this

involves removing and adding sections of

RNA the messenger RNA then moves out of

the nucleus into the cytoplasm protein

factories in the cytoplasm called

ribosomes bind to the messenger RNA the

ribosome reads the code in the messenger

RNA to produce a chain made up of amino

acids there are 20 different types of

amino acid transfer RNA molecules carry

the amino acids to the ribosome the

messenger RNA is read 3 bases at a time

as each triplet is read a transfer RNA

delivers the corresponding amino acid

this is added to a growing chain of

amino acids once the last amino acid has

been added the chain folds into a

complex 3d shape to form the protein

you

protein synthesis translation inside the

body the process of translation occurs

within every single cell each cell has a

nucleus after transcription mRNAs move

out of the nucleus and enter the

cytoplasm this mRNA strand acts as a

template for protein synthesis present

in the cytoplasm is an enzyme amino acyl

tRNA synthetase the enzyme macro

molecule has two binding sites one site

recognizes the amino acid methionine

this is followed by the binding of the

ATP molecule and release of

pyrophosphate resulting in activation of

amino acid finally the tRNA and the

activated amino acid bind together this

amino acyl ated tRNA is known as met

tRNA and is released from the enzyme

this marks the commencement of first

stage of protein synthesis the

initiation stage during the eighth

initiation stage a small subunit of a

ribosome binds to the mRNA strand the

mRNA strand is made up of codons which

are sequences of 3 bases then the

ribosome subunit moves along the mRNA in

five prime to three prime direction

until it recognizes the Aug codon or the

initiation codon

at this point net tRNA possessing the

anticodon UAC pairs up with the Aug

codon of the M RNA then a large subunit

of ribosome combines with a small

ribosomal subunits the lab subunit shows

three sides the acceptor site or the a

site v dial site or the P site the exit

site or the e site this whole unit forms

the initiation complex this is followed

by the elongation stage during this

stage another tRNA carrying molecule of

an amino acid approaches the M RNA

ribosome complex and fits in the a site

then a bond is formed between methionine

and the amino acid molecule on the tRNA

as a result met tRNA becomes d isolated

the ribosome then advances a distance of

one codon and the D isolated tRNA shifts

to the east side from where it

dissociates meanwhile another tRNA

carrying an amino acid molecule attaches

to the a site this is followed by the

binding of the amino acid molecules

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repetition of this process leads to the

formation of an amino acid chain

this event is called elongation finally

when the UAG codon or the stop codon

reaches the a site elongation is

terminated termination is the last stage

of protein synthesis the chain of amino

acid molecules is released from the

ribosome this released amino acid chain

is the protein and this part of protein

synthesis is known as translation then

the tRNA detaches from the mRNA ribosome

detaches and dissociates into its small

and large subunits

summary protein synthesis shows that the

first stage involves the binding of met

tRNA to M RNA and the small subunit of

the ribosome the larger subunit of

ribosome then combines with a small

subunit second stage is the elongation

stage in this stage the incoming amino

acyl tRNA fits in the a site then a bond

is formed between methionine and the

amino acid molecule on the tRNA the

process is repeated until a chain of

amino acid molecules is formed the last

stage of protein synthesis is the

termination stage when the ribosome

reaches the stop codon you AG elongation

stops and the newly formed a minor acid

chain which is the protein macro

molecule detaches from the ribosome

subsequently ribosomal subunits along

with the tRNA dissociate from the M RNA

in order for our bodies to function we

need to supply them with a variety of

nutrients we get from our diet

our bodies cannot use the food as it is

when it enters our digestive system the

process of chemical digestion uses

different proteins and enzymes to break

down the food particles into usable

nutrients our cells can absorb

and where are the instructions to

manufacture these and all the different

types of proteins we need to stay alive

the instructions to make proteins are

contained in our DNA DNA contains genes

a gene is a continuous string of

nucleotides containing a region that

codes for an RNA molecule this region

begins with a promoter and ends in a

terminator genes also contain regulatory

sequences that can be found near the

promoter or at a more distant location

for some genes the encoded RNA is used

to synthesize a protein in a process

called gene expression for these genes

expression can be divided into two

processes transcription and translation

in eukaryotic cells transcription occurs

in the nucleus where DNA is used as a

template to make messenger RNA then in

translation which occurs in the

cytoplasm of the cell

the information contained in the

messenger RNA is used to make a

polypeptide

during transcription the DNA in the gene

is used as a template to make a

messenger RNA strand with the help of

the enzyme RNA polymerase this process

occurs in three stages initiation

elongation and termination during

initiation the promoter region of the

gene functions as a recognition site for

RNA polymerase to bind this is where the

majority of gene expression is

controlled by either permitting or

blocking access to this site by the RNA

polymerase binding causes the DNA double

helix to unwind and open then during

elongation the RNA polymerase slides

along the template DNA strand

as the complementary bases pair up the

RNA polymerase links nucleotides to the

3 prime end of the growing RNA molecule

once the RNA polymerase reaches the

terminator portion of the gene the

messenger RNA transcript is complete and

the RNA polymerase the DNA strand and

the messenger RNA transcript dissociate

from each other

the strand of messenger RNA that is made

during transcription includes regions

called

exons that code for a protein and

non-coding sections called introns in

order for the messenger RNA to be used

in translation the non-coding introns

need to be removed and modifications

such as a five prime cap and a 3 prime

poly a tail are added this process is

called introns splicing and is performed

by a complex made up of proteins and RNA

called a spliceosome

this complex removes the intron segments

and joins the adjacent exons to produce

a mature messenger RNA strand that can

leave the nucleus through a nuclear pore

and enter the cytoplasm to begin

translation

how is the information in the mature

messenger RNA strand translated into a

protein the nitrogenous bases are

grouped into three letter codes called

codons

the genetic code includes 64 codons most

codons code for specific amino acids

there are four special codons one that

codes for start and three that code for

stop

translation begins with the messenger

RNA strand binding to the small

ribosomal subunit upstream of the start

codon each amino acid is brought to the

ribosome by a specific transfer RNA

molecule the type of amino acid is

determined by the anticodon sequence of

the transfer RNA

complementary base pairing occurs

between the codon of the messenger RNA

and the anticodon of the transfer RNA

after the initiator transfer RNA

molecule binds to the start codon the

large ribosomal subunit binds to form

the translation complex and initiation

is complete

in the large ribosomal subunit there are

three distinct regions called the e P

and a sites

during elongation individual amino acids

are brought to the messenger RNA strand

by a transfer RNA molecule through

complementary base pairing of the codons

and anticodons each Eddie codon of a

transfer RNA molecule corresponds to a

particular amino acid

a charged transfer RNA molecule binds to

the a site and a peptide bond forms

between its amino acid and the one

attached to the transfer RNA molecule at

the P site

the complex slides down one codon to the

right where the now uncharged transfer

RNA molecule exits from the e site and

the a site is open to accept the next

transfer RNA molecule

elongation will continue until a stop

codon is reached

a release factor binds to the a site at

a stop codon and the polypeptide is

released from the transfer RNA in the P

site the entire complex dissociates and

can reassemble to begin the process

again at initiation the purpose of

translation is to produce polypeptides

quickly and accurately

after dissociation the polypeptide may

need to be modified before it is ready

to function

modifications take place in different

organelles for different proteins

in order for a digestive enzyme to be

secreted into the stomach or intestines

the polypeptide is translated into the

endoplasmic reticulum

modified as it passes through the Golgi

then secreted using a vesicle through

the plasma membrane of the cell into the

lumen of the digestive tract

proteins are needed for most

physiological functions of the body to

occur properly such as breaking down

food particles in digestion and the

processes of transcription and

translation make the production of

proteins possible

the job of this mRNA is to carry the

genes message from the DNA out of the

nucleus to a ribosome for production of

the particular protein that this gene

codes for there can be several million

ribosomes in a typical eukaryotic cell

these complex catalytic machines use the

mRNA copy of the genetic information to

assemble amino acid building blocks into

the three-dimensional proteins that are

essential for life let's see how it

works the ribosome is composed of one

large and one small subunit that

assemble around the messenger RNA which

then passes through the ribosome like a

computer tape

the amino acid building blocks that's

the small glowing red molecules are

carried into the ribosome attached to

specific transfer RNAs that's the larger

green molecules also referred to as tRNA

the small subunit of the ribosome

positions the mRNA so that it can be

read in groups of three letters known as

a codon each codon on the MRNA matches a

corresponding anticodon on the base of a

transfer RNA molecule the larger subunit

of the ribosome removes each amino acid

and joins it onto the growing protein

chain as the mRNA is ratcheted through

the ribosome the mRNA sequence is

translated into an amino acid sequence

there are three locations inside the

ribosome designated the a site the P

site and the e site the addition of each

amino acid is a three step cycle first

the tRNA enters the ribosome at the a

site and is tested for a codon anticodon

match with the mRNA next provided there

is a correct match the tRNA is shifted

to the P site and the amino acid it

carries is added to the end of the amino

acid chain the mRNA is also ratcheted on

three nucleotides or one codon thirdly

the spent tRNA is moved to the east side

and then ejected from the ribosome to be

recycled as the protein synthesis

proceeds the finished chain emerges from

the ribosome it folds up into a precise

shape determined by the exact order of

amino acids thus the central dogma

explains how the four-letter DNA code is

quite literally turned into flesh and

blood

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