Shri Shivaji Science College,
Amravati
Department of botany
Presentation Topic- Ribosomes
Presented by : Shruti Ramesh Mahulkar
Class :BSC 3rd year
Ribosome
01 Definition
02 Discovery
03 Occurance
04 Structure
05 Type
06 Function
Defination
Ribosomes are cellular organelles
responsible for protein synthesis in all
living cells. They are composed of RNA and
protein molecules and exist in both
prokaryotic and eukaryotic cells.
Ribosomes function by translating genetic
information encoded in messenger RNA
(mRNA) into specific sequences of amino
acids, which then fold into functional
proteins.
Discovery
Albert Claude ( 1941)
01
02
First observed ribosomes and called them as "microsomes "
01 which were actually the fragments of rough endoplasmic
reticulum.
03
Robinson & Brown (1953)
First observed ribosomes in plant cells (bean
02
roots).
03
George Emil Palade (1955)
Isolated ribosomes from animal cells. 04
Richard.B.Roberts (1958)
Coined the term ribosomes.
04
Occurence
OF RIBOSOMES
Occurs in both prokaryotic cells and eukaryotic
cells.
In Prokaryotic cells, ribosomes often occurs free in
the cytoplasm. (called free ribosomes)
In Eukaryotic cells, ribosomes occurs freely in the
cytoplasm or remain attached to the outer
surface of the membrane of endoplasmic
reticulum. (called bounded ribosomes)
Absent in mature mammalian RBCs and sperms.
Structure Of Ribosomes
01 02 03
Ribosome is composed of Ribosomes are different Each Ribosome consists of
specialized RNA called from other organelles two subunits, a larger one
ribosomal RNA (rRNA) and because they have no called large subunit and a
essential protiens. membrane around them. smaller one called small
[ rRNA (60%) + Protiens i.e., ribosomes are subunit.
(40%) = Ribosome ] membraneless.
Types Of Ribosomes
Found in Prokaryotic cells as well as Chloroplast and
Mitochondria.
Large Subunit - 50S
Small Subunit - 30S
Lighter in weight (approx 2.7-3.0 million Daltins )
Three molecules of rRNA.
Two molecules in Large Subunit (235 + 5S)
One molecule in Small Subunit ( 165 )
55 protein molecules, 34 in larger and 21 in smaller
subunit.
70's
Types Of Ribosomes
Found in Eukaryotic cells.
Large Subunit - 60S
Small Subunit - 40S
Heavier in weight ( approx 4.0-4.5 million Daltons)
Four molecules of rRNA.
Three molecules in Large Subunit (28S+ 5.8S+ 5S).
One molecule in Small Subunit (18S).
73 protein molecules, 40 in larger and 33 in smaller
subunit.
80's
Functions Of
Ribosomes
Perform protein synthesis
along with the help of mRNA
and tRNA.
The process is called
Translation.
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