Structure and Functions of RNA and MCQs for GPAT, NEET, GATE and CSIR NET Exams

Structure and Functions of RNA and MCQs for GPAT, NEET, GATE and CSIR NET Exams

RNA is similar to DNA. It is a long unbranched macromolecule which consists of nucleotides joined by phosphodiester bonds. The four bases of RNA include:

  • Purine base: adenine and guanine
  • Pyrimidine base: cytosine and uracil

Types of RNA:- cell contains majorly 3 types of RNA

  1. Messenger RNA(mRNA)
  2. Transfer RNA (t-RNA)
  3. Ribosomal RNA (r-RNA)

All the three types of RNA have its individual role in the biosynthesis of protein. Each type of RNA differs from another by its size and function.

Messenger RNA

The m-RNA is only 5-10% of total cellular RNA. It is synthesized in the nucleus as heterogenous RNA (hm-RNA) but then it is processed into its functional form m-RNA. The m-RNA carries genetic information in the form of codons. Some unique characteristics of m-RNA include:

  • 5’ end of m-RNA is covered or caped by 7-methylguanosine tri-phosphate. This cap helps to recognize m-RNA during protein synthesis and helps to stabilize the m-RNA.
  • The 3’ end of m-RNA is attached to pony A-tail. This tail consists of series of adenylate residues (20-250 nucleotides in length joined by phosphodiester bonds).

This picture is taken only for educational purpose from classconnection.s3.amazonaws.com

Align

 

Link To

 

Functions of m-RNA

  1. It serves as template for protein synthesis
  2. It transfers information from DNA to protein synthesizing machinery.
  3. If the m-RNA codes only for single one peptide, the m-RNA is called mono-cistronic. And if it codes for two or more different polypeptide then m-RNA is called polycistronic. In eukaryotes, mostly the m-RNA is mono-cistronic.

Transfer RNA

The transfer RNA forms a structure that appears like clover leaf. It consists of 74-95 nucleotides. There are at least 20 different t-RNA molecules, one for each amino acid for the synthesis of proteins. Many amino acid has more than one t-RNA.

The t-RNA consists of 4 arms:

  • The acceptor arm- it consist of base paired stem that terminates in the sequence CCA at the 3’ end. It is the attachment site for the amino acid which is carried by t-RNA.
  • The D-arm- it is named due to the presence of dihydrouridine (D)
  • The anti-codon arm- contains the anticodon that pairs with codon on m-RNA. Anti-codon has nucleotide sequence opposite to the codon of m-RNA.
  • The T psi C arm- it contains both ribothymidine (T) and pseudo-uridine (psi)

This picture is taken only for educational purpose from upload.wikimedia.org

Align

 

Link To

 

Function of t-RNA

T-RNA carries amino acid in the activated form to the ribosome for the biosynthesis of protein.

Ribosomal RNA

The RNA of the ribosome is called r-RNA. Ribosome is a nucleoprotein which acts as a machinery for the biosynthesis of protein. Ribosome is composed of small and large subunits. Ribosomes of both eukaryotes and prokaryotes have their sedimentation coefficients; which are 70S for prokaryotes and 80S for eukaryotes. These coefficients are then subdivided. Thus 70S yields 50S, 30S and 80S yields 60S, 40S. Each subdivided unit is composed of one or more strand of r-RNA and no. of protein molecules.

Prokaryotic ribosome contains 3 r-RNA molecules, and eukaryotic ribosome contains four r-RNA molecules.

Functions of r-RNA

  • It is important for maintaining the ribosomal structure and also participates in protein synthesis
  • It binds m-RNA to ribosome
  • It also performs some catalytic activity as an enzyme ribozyme.

Multiple Choice Questions (MCQs)

1. Which of the following is a long un-branched macromolecule?
A. Chromosomes

B. DNA

C. RNA

D. All of the above

2. Which of the following base is not present in RNA?
A. Cytosine

B. Thymine

C. Uracil

D. Guanine

3. Which type of sugar is present in RNA?
A. Pentose sugar

B. Ribose sugar

C. Deoxy-ribose sugar

D. Both B and c

4. What is the full form of m-RNA?
A. Magnetic RNA

B. Messenger RNA

C. Mitochondrial RNA

D. None of the above

5. Which of the following category differentiates the different types of RNA?
A. Size

B. Shape

C. Function

D. Both A and C

6. Which of the following arm of t-RNA serve as side of attachment for amino acid?
A. Acceptor arm

B. D- arm

C. Anticodon arm

D. t-psi arm

7. In RNA, nucleotides are joined by which type of bond?
A. Glycosidic bond

B. Phosphodiester bond

C. Both

D. None

8. The m-RNA is synthesized in the nucleus in which form?
A. Heterogenous RNA

B. Homogenous RNA

C. Homologous RNA

D. None of the above

9. Match the following-

A. m-RNA     1. Binds ribosomes to m-RNA

B. t-RNA       2. Carries active amino acid to ribosomes

C. r-RNA       3. Serves as template for protein synthesis

10. Which of the following binds the m-RNA to the ribosome?
A. t-RNA

B. Nucleus

C. m-RNA itself

D. None of the above

11. The eukaryotic ribosome contains how many r-RNA molecules?
A. 3

B. 2

C. 4

D. 6

12. Which of the following serves as template for protein synthesis?
A. t-RNA

B. r-RNA

C. m-RNA itself

D. None of the above

13. Which of the following statement is NOT true?

A. In prokaryotes, mostly the m-RNA is mono-cistronic

B. The acceptor arm consist of base paired stem

C. r-RNA perform some of the enzymatic activity

D. Prokaryotic ribosome contains 3 r-RNA

14. Which of the following is the function of r-RNA?
A. Maintains shape of ribosome

B. Protein synthesis

C. Binds m-RNA and ribosome

D. All of the above

15. How is the nucleotide sequence in the anti-codon arm of t-RNA?
A. Same as in codon

B. Opposite to the codon sequence

C. Not constant

D. None of the above

ANSWERS-

1. RNA
2. Thymine
3. Ribose sugar
4. Messenger RNA
5. Both A and c
6. Acceptor arm
7. Phosphodiester bond
8. Heterogenous RNA
9. A – 3 B – 2 C – 1
10. None of the above
11. 4
12. m-RNA
13. In prokaryotes, mostly the m-RNA is mono-cistronic
14. All of the above
15. Opposite to the codon sequence

For More Standard and Quality Question Bank you can Join Our Test Series Programme for GPAT, NIPER JEE, Pharmacist Recruitment Exam, Drug Inspector Recruitment Exams, PhD Entrance Exam for Pharmacy

Participate in Online FREE  GPAT  TEST: CLICK HERE

Participate in Online FREE  Pharmacist  TEST: CLICK HERE 

Participate in Online FREE  Drug Inspector  TEST: CLICK HERE 

Participate in CSIR NET JRF Mock Test

Participate GATE Mock Test

REFERENCE:- 1. Pankaja Naik- Biochemistry; 4th edition; page no:- 133-136

 

 

Leave a Reply

Your email address will not be published. Required fields are marked *

3 − 2 =

×
Free Video Lectures of Pharmacy Exams
Apply now

Developed By Connect Globes