The structure,Function and Biosynthesis of the Ribosome
Compare two classes of ribosomes(80S, 70S):
* Both classes of ribosomes have almost the same structures and functions. * Their sizes are different from each other.
What is nucleolus?
* The nucleolus contains large loops of DNA emanating from several chromosomes (Chromosomes 13, 14, 15, 21 and 22)
What does initiate translation in Prokaryotes? What does initiate translation in Eukaryotes?
-It's binding of the 16S ribosomal RNA to the shine-dalgarno sequence. -Is binding of the complete small40S subunit to the cap on the messenger RNA
Where are free ribosomes found?
-oocytes -Embryonic cells -keratinocytes -prokaryotes
• (The gene for 5S r-RNA is located on chromosome 1, and it is transcribed separately in the nucleus) • 55 rRNA then pass to the nucleolus and 5S, 1..... and 2.... rRNA molecules incorporate into the large subunits with the 3 ......... • 4....... rRNA binds some structural ribosomal-proteins and assembles the small subunits.
1.5.8S 2.28S r-RNA 3.ribosomal proteins 4.18S
The precursor RNA is cleaved to give one copy each of .............rRNA, .......rRNA and the ........rRNA of the ribosome.
28S-18-5.8
The 80 S ribosomes are composed of ....% RNA and.........%proteins.
40%-60%
Precursor RNA molecule or............
45S r-RNA
• (The gene for ....... r-RNA is located on chromosome 1, and it is transcribed separately in the nucleus)
5S
The 70 S ribosomes are composed of .....% RNA and ........% protein.
60%-40%(if you were taking exam of uni choose this one,if he didn't mention 70S or80 S)
.......ribosomes present in Prokaryotes, mitochondrain and chloroplast., called as............
70 S-prokaryotic ribosomes(free ribosomes)
........ribosomes present in all Eukaryotic cells, also called as eukaryotic ribosomes.
80 S ribosomes(membrane-bound ribosomes:bound to the nucleus membrane and ER membrane)
Name and explain the functional sites on the ribosome:
> Aminoacyl-site (A site) accepts the new coming t-RNA molecule charged with an amino acid > Peptidyl-site (P site) holds the t-RNA molecule that is linked to the extending end of the polypeptide chain > Exit site (E site) releases the deacylated tRNA from the ribosomes > m-RNA-binding site is the point where mRNA to be translated into protein will bind
What happens to ribosomal subunits at the end of each round of protein synthesis?
At the end of each round of protein synthesis, the ribosomal subunits are released and rejoin the common pool in the cvtosol
What does Tetracycline do?
Blocks binding of aminoacyl-tRNA to A-site of ribosome.
What does chloramphenicol do to the protein synthesis in prokaryotes?
Blocks the peptidyl transferase reaction on ribosome
What does Cyclohgeximide do to the protein synthesis in prokaryotes?
Blocks the translocation reactions on ribosome
What does Erythromycin do to protein synthesis in prokaryotes?
Blocks the translocation reactions on ribosome
The ribosomes bound to RER are versatile and can synthesize proteins that................
Can be used inside or outside of the cell
What is the structure of 70 S ribosome?
Consists of 2 subunits, 50S larger smaller subunit subunit and 30S smaller subunit.
Ribosomal proteins are synthesized in the........
Cytoplasm
Ribosomes can be found ............
In all kinds of cells
What is Svedberg(S)?
Is the measurement unit of the rate of sedimentation in centrifugation.
What does the rate of sedimentation depend on?
It depends upon the size and shape of the molecule rather than its molecular weight.
What is 5S r-RNA?
It is a structural and functional component of the large subunit of the ribosome.
What is the structure of 80 S ribosome?
It is consisted of 2 subunits, 60 S larger subunit and 40 S smaller subunit.
80 S ribosomes occur as ...................., bound to.........and .............
Membrane -rough endoplasmic reticulum(RER) -outer nuclear membrane
r-RNA genes are present on the .......on the .......of the .....................
NOR-satellite-acrocentric chromosomes13.14,15,21 and 22
Do the two subunits of ribosome unite each other in the nucleus?
No 🔹The two subunits are transferred to cytoplasm as two separate subunits 🔹In the presence of an mRNA to be translated into protein,they unite each other to form mature ribosome
> In prokaryotes, ......m-RNA usually runs successively through the several ........ in a cluster producing......................
One-ribosomes-multiple copies of a protein
5S rRNA is synthesized .............(where?)
Outside of the nucleolus.
70 S ribosomes and present in .........., .........and ..........
Prokaryotes, mitochondrion and chloroplast.
Are these ribosomal RNA (18S, 28S, 5.8S)are made by.............except for 5SrRNA which is made by...........
RNA polymerase1-RNA polymerase3
r-RNA genes are transcribed by........
RNA polymerases
..............provide the structural core of each ribosomal subunits.
Ribosomal RNAs
What is Ribosomal Biogenesis?
Ribosome biogenesis is the process of ribosome synthesis.
A common pool of ribosomes is used to synthesize the proteins that ..............and those that are...............
Stay in the cytosol-those that are transported into the ER.
In 70S , S refers to?
Svedberg unit sedimentation coefficient
Free ribosomes synthesize proteins ..........
That will function in the cytosol Structural proteins of the cell which may remain in the cytoplasm or be targeted to particular organelles (the enzymes of glycolysis, tubulins, actin, histones, transcription factors, mitochondrial or nuclear structural proteins etc.)
In eukaryotes, typically many ribosomes translate the mRNA simultaneously. TRUE OR FALSE?
True each ribosome begin at the 5prime end of the mRNA and progresses steadily towards the 3prime end. These multiple initiations allow the cell to make much more protein from a single message.
Polysomes consist of :
a group of ribosomes connected by a strand of m-RNA molecule during the translation
versatile:
able to adapt or be adapted to many different functions or activities.
What is peptidyl transferase?
an enzyme that catalyzes the addition of an amino acid residue in order to grow the polypeptide
r-RNA genes are present on the NOR on the satellites of the acrocentric chromosomes 13, 14, 15, 21 and 22 first of all,they are transcribed altogether forming...........................
an r-RNA complex of 45S
What kind of protein do the RER attached ribosomes produce?
b) Attached ribosomes are united the membranes of the rough endoplasmic reticulum ( RER) and synthesize 🔹proteins that are exported to the part of the cell's membranes. 🔹Secretory proteins(collagen, peptide hormones) 🔹lysosomal enzymes 🔹glycoproteins of plasma membrane
How do different antibiotics have influence on bacterial ribosomes?
different antibiotics bind to different regions of bacterial ribosomes, they often inhibit different steps in the synthetic process.
70 S ribosomes occur as ............., also present in ....................and................of eukaryotic cells.
free ribosomes in cytoplasm of PROKARYOTES -mitochondrion-chloroplast
Ribosome is a ................organelle.
non-membranous
In the cytoplasm free ribosomes are found as individual granules or in clusters called.... or ..........
polysomes-polyribosome
.........and ......... catalyze many of the reactions on the ribosomes during the proteins synthesis.
r-RNA, proteins
Ribosomes are made up of................+ .............+............
rRNA-ribosomal protein-divalent ions manily Mg++
Each chromosomal part [..............]contains a cluster of........
• Each chromosomal parts [nucleolar organizer region (NOR)] contains a cluster of r-RNA genes • r-RNA genes transcribed by RNA polymerases
Where does the Ribosome Biogenesis take place in Prokaryotes and Eukaryotes?
• In prokaryotic cells, it takes place in the cytoplasm with the transcription of many ribosomal genes. -In eukaryotes, it takes place both in the cell cytoplasm and in the nucleolus of eukaryotic cells.
Recent......................... and.................. of eukaryotic ribosomes and ribosomal subunits now provide an unprecedented opportunity to explore mechanisms of eukaryotic translation and its regulation in atomic perspective.
🔹cryo-electron microscopy reconstructions , 🔹X-ray crystal structures
