1. Which of the following is the site of protein synthesis in a cell?
a) Nucleus
b) Cell membrane
c) Vacuole
d) Ribosomes
Explanation: Ribosome is the site of protein synthesis in a cell. They are small organelles present inside the cell in two forms, which are membrane-free ribosomes and ER membrane-bound ribosomes.
2. What does the ribosome consist of?
a) Two subunits of equal sizes
b) Two large and two small subunits
c) Two large and one small subunit
d) One large and one small subunit
Explanation: Ribosomes are small organelles that are known to synthesize protein. In all organisms, they are composed of two subunits, one large and one small subunit. In prokaryotes, the sizes of the small and large subunits are the 30S and 50S respectively. In eukaryotes, the sizes of the small and large subunits are the 40S and 60S respectively.
3. Which of the following was used by Carl Woese to build the prokaryotic phylogenetic tree?
a) 5.8S rRNA gene
b) 5S rRNA gene
c) 23S rRNA gene
d) 16S rRNA gene
Explanation: The 16S rRNA gene was used by Carl Woese to build the prokaryotic phylogenetic tree. This gene is present in all prokaryotic cells. Apart from this gene, there are few other genes like 5S rRNA, 23S rRNA gene which is present in prokaryotic cells.
4. There is no difference between prokaryotic and eukaryotic ribosomes.
a) True
b) False
Explanation: The above statement is false. There are differences in prokaryotic and eukaryoticribosomes in terms of size and composition. The eukaryotic ribosome is the 80S and the prokaryotic ribosome is 70S in size.
5. Which of the following represents the correct constituents of a prokaryotic ribosome?
a) 16S, 23S, and 5.8S rRNA
b) 23S, and 5.8S rRNA
c) 16S and 5S rRNA
d) 16S, 23S, and 5S rRNA
Explanation: The correct constituents of a prokaryotic ribosome are 16S, 23S, and 5S rRNA. A prokaryotic ribosome has a size of 70S. It is composed of a larger subunit (the 50S) and a smaller subunit (30S).
6. Which of the following represents the correct constituents of a eukaryotic ribosome?
a) 16S, 28S, and 5S rRNA
b) 16S, 28S, and 5.8S rRNA
c) 18S, 28S, and 5.8S rRNA
d) 18S, 28S, 5S, and 5.8S rRNA
Explanation: The correct composition of a eukaryotic ribosome is 18S, 28S, 5S, and 5.8S rRNA. The size of the eukaryotic ribosome is the 80S. 16S rRNA is not a constituent of the eukaryotic ribosome.
7. Find the odd one out.
a) 18S rRNA
b) 28S rRNA
c) 5.8S rRNA
d) 16S rRNA
Explanation: 18S, 28S, and 5.8S rRNA are part of a eukaryotic ribosome. 16S rRNA is a constituent of the prokaryotic ribosome. Hence, 16S rRNA is the odd one out.
8. Proteins that are to be incorporated into cytoplasmic organelles are synthesized on ER membrane-bound ribosomes. Whereas, proteins that are to be imported into the ER-Golgi system are synthesized on free ribosomes in the cytosol.
a) True
b) False
Explanation: The above statement is false. Proteins that are to be incorporated into cytoplasmic organelles are synthesized on free ribosomes in the cytosol. Whereas, proteins that are to be imported into the ER-Golgi system are synthesized on ER membrane-bound ribosomes.
9. Find the odd one out.
a) ER proteins
b) Lysosomal proteins
c) Golgi complex proteins
d) Soluble cytosolic proteins
Explanation: ER proteins, lysosomal proteins,and Golgi complex proteins are synthesized by ER bound ribosomes. Whereas, soluble cytosolic proteins are synthesized by free ribosomes in the cytosol.
10. Which of the following protein is not synthesized by membrane-free ribosomes?
a) Chloroplast proteins
b) Peroxisomal proteins
c) Extrinsic membrane proteins localized to the cytoplasmic surface
d) Extrinsic membrane proteins localized to the extra-cytoplasmic surface
Explanation: Extrinsic membrane proteins localized to the extra-cytoplasmic surface are not synthesized by membrane-free ribosomes. ER membrane-bound ribosomes synthesize the extrinsic membrane proteins that are localized to the extra-cytoplasmic surface. Chloroplast proteins, peroxisomal proteins, and extrinsic membrane proteins localized to the cytoplasmic surface are synthesized by membrane-free ribosomes.