This set of Life Sciences Multiple Choice Questions & Answers (MCQs) focuses on “Ribosome”.
1. Genetic information stored in mRNA is translated to polypeptide by ___________
a) Ribosome
b) Nucleus
c) Endoplasmic reticulum
d) Golgi apparatus
View Answer
Explanation: Ribosomes are ribonucleoproteins which are made up of RNAs and protein. These are used to translate genetic information stored in mRNA to polypeptides. These are globular in structure.
2. Eukaryotes have 80S ribosome.
a) True
b) False
View Answer
Explanation: Eukaryotes have 80S ribosome, each consisting of small subunit (40S) and large subunit (60S) while prokaryotes have 70S ribosome with small subunit (30S) and large subunit (50S).
3. Which of the following ribosomal RNA does not take part in rDNA organization of E.coli?
a) 5S RNA
b) 23S RNA
c) 16S RNA
d) 5.8S RNA
View Answer
Explanation: The transcription unit of prokaryotes is made up of three ribosomal RNAs i.e. 16S, 23S, and 5S. The organization of ribosomal RNAs is similar in eukaryotes also but the size of RNA varies.
4. What is the sedimentation coefficient of mitochondrial ribosome of humans?
a) 70S
b) 55S
c) 80S
d) 60S
View Answer
Explanation: Eukaryotes consists of two types of the ribosome, cytosolic and organellar. The cytosolic ribosome is of 80S while organellar ribosome of mitochondria and chloroplast is smaller in size than cytosolic ribosome and bear resemblance to bacterial ribosome.
5. Which of the following Scientist discovered ribosome for the first time?
a) George Emil Palade
b) Theodor Schwann
c) Antonie van Leeuwenhoek
d) Robert Hook
View Answer
Explanation: George Emil Palade, Romanian-American cell biologist has first observed ribosome as dense particles using an electron microscope.
6. Which of the following is not a sorting signal present of protein?
a) Signal patch
b) Signal peptide
c) Carbohydrate sequence
d) Amino acid sequence
View Answer
Explanation: Sorting signals present on proteins help them to transport and target to specific organelles such as ER, mitochondria, nucleus, plastids etc. Sorting signals present on protein can be a signal patch or signal peptide which is in the form of an amino acid sequence.
7. Which of the following statement is defines polysomes?
a) Lysosomal aggregation
b) Multiple units of ribosomes
c) Attachment of many ribosomes to common mRNA
d) Attachment of many mRNA to ribosomes
View Answer
Explanation: Polysome is also known as polyribosome, it is a structure where a single mRNA holds a number of ribosomes translocating in 5’ to 3’ direction.
8. Which of the following transport involves translocation of the protein from cytosol to the nucleus?
a) Transmembrane transport
b) Vesicular transport
c) Non-gated transport
d) Gated transport
View Answer
Explanation: Translocation of protein from cytosol to nucleus takes place by nuclear pore complex which is a gated channel. Nuclear pore complex works as a selective gate which allows transport of specific macromolecules.
9. Name the site where secreted protein synthesized?
a) ER membrane bound ribosomes
b) Mitochondrial ribosome
c) Membrane free ribosome
d) Chloroplast ribosome
View Answer
Explanation: Secreted proteins pass through ER-Golgi system, so, these are synthesized on ER membrane-bound ribosomes while proteins that are imported into organelles like mitochondria, nucleus, and chloroplast are synthesized on membrane free ribosomes.
10. Name the antibiotic which inhibits protein synthesis in eukaryotes?
a) Penicillin
b) Cycloheximide
c) Cinhonine
d) Chlorophenicol
View Answer
Explanation: Cyclohexamide produced by the Streptomyces griseus, and interfere with the translocation step of protein synthesis and block translational elongation in eukaryotes.
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