Question

The subunits of 80S ribosome will be
A. The 40S and 40S
B. The 60S and 40S
C. The 60S and 20S
D. 55S and 25S

Answer 1

Eukaryotic ribosome has two unequal subunits. Ribosomes are of two major groups prokaryotic and eukaryotic. Eukaryotic ribosomes, in turn, are of three types,cyto ribosomes, mitoribosomes, and chlor ribosomes.

Complete answer:
Cyto Ribosomes are seen in the cytoplasmic matrix, mitoribosomes in the mitochondrial matrix, and chlor ribosomes in the chloroplast matrix. The average sedimentation value of centrifugation of prokaryotic ribosome is the 70S, that of eukaryotic cyto ribosome is 80S, animal mitoribosome is 55S, and that of chlor ribosome is 78S. All classes of the ribosome have an almost similar structure. Each of them consists of two subunits, one larger subunit, and one smaller subunit. The larger subunit is almost dome- shaped, and the smaller one is placed above it just like a cap. The subunits of the 70S ribosome are 50S and 30S, that of 80S cyto ribosome and 78S chloro ribosome are 60S and 40S and the mitoribosome is 40S and 30S.
- Ribosomes are tiny particles of ribonucleoprotein, which serve as the factories of protein production. - Ribosomes are of two major groups prokaryotic and eukaryotic.
- Prokaryotic ribosomes are formed of 54 kinds of proteins and 3 kinds of rRNAs. The rRNAs are 5S,16S, and 23S rRNAs.
- Eukaryotic cyto ribosomes are of two kinds, freely dispersed and attached.
- The 80S eukaryotic cyto ribosome has two unequal subunits. Their larger subunit is formed of 40 kinds of proteins and 28S, 5S, and 5. 8S rRNAs. The Smaller subunit is formed of 30- 40 proteins and 18S rRNAs.
So, the correct answer is ‘60S and 40S’.

Note: 'S' values are not additive. 'S' represent the Svedberg unit- the unit of measurement of sedimentation coefficient in ultracentrifugation. Ribosomes are present in all prokaryotic and eukaryotic cells except in mature mammalian erythrocytes.