Virus, Viroids and Prions: NCERT Notes, Differences and MCQs for NEET
By Pavan Chaturvedi
Welcome to Chaubey Biology Hub, your premier destination for high-quality, NCERT-aligned medical entrance preparation. We take pride in delivering content that doesn't just mirror textbooks but decodes them. This guide on Virus, Viroids and Prions: NCERT Notes, Differences and MCQs for NEET is meticulously crafted to meet the rigorous standards of the NTA NEET-UG syllabus, focusing exclusively on the core concepts that matter most.
Before exploring the structural and metabolic diversity of the Virus, Viroids and Prions: NCERT Notes, Differences and MCQs for NEETensure you have reviewed our previous post on Fungi: Notes, Classification & NEET Important MCQs, and Principles to understand the foundational criteria used to classify these prokaryotic organisms in your NEET journey.
Table of Contents
- Introduction to Acellular Organisms
- What are Viruses? (Structure and Discovery)
- Understanding Viroids (T.O. Diener's Discovery)
- Prions: The Infectious Proteins
- Comparison Table: Virus vs Viroids vs Prions
- Important NEET MCQs
Introduction
- There are so many structure which are non cellular or acellular.
- They exist their presence around the cellular organism. They have some significant impact on living organism.
 |
| Tobacco Mosaic virus and Bacteriophage |
Virus
- A Virus is non cellular organism that have a crystalline structure outside the living cell.
- Once it come with contact of living cell than it uses the system of host cell and start to replicate with in host cell.
📌 Virus Lecture: Important Timestamps
00:00 - Intro: Virus General Account
- 00:48 - Louis Pasteur: The term 'Virus'
- 01:38 - D.J. Ivanovsky: Discovery of TMD (1892)
- 02:48 - Virus size vs Bacteria
- 03:17 - M.W. Beijerinck: Contagium Vivum Fluidum
- 04:46 - W.M. Stanley: Crystallization (1935)
- 05:57 - General Properties of Virus
- 06:50 - Virus behavior: Outside vs Inside Cell
- 08:08 - Why Virus is an Obligate Parasite?
- 08:19 - Bacteriophage: Viruses that infect Bacteria
Remember : Acellular organism like virus, Viroids and Prions are not getting any place in any Classification.
- Term virus has been taken from the word "Venom" by the Louis Pasteur.
- Dmitri Ivanowsky in 1892 identified some disease causing particle from Tobacco mosaic disease. These particles are smaller than bacteria because they can pass bacteria proof filters.
💡 Read also to understand about the Kingdom Monera: General Characters, Classification & NEET MCQs
- M.W. Beijerineck in 1898 extracted the some fluid from plant affected by Tobacco Mosaic disease. This infected fluid was renamed by "Contagium Vivum Fluidum"
- W.M. Stanley in 1935 crystallized the virus particle and these Crystal are made up of protein.
- Virus is non living outside the living cell and behaves like obligate parasite.
- Virus has a protein coat and its infectious genetic material is enclosed inside the protein cost.
- The protein coat is called capsid which is made up of small subunit called capsomere.
- Capsomeres are arranged helically or polyhedral geometric form.
- The genetic material or nucleic acid inside the protein is either DNA or RNA which contain nucleoprotein.
- Since virus has no ribosome , mitochondria or other cell organs hence virus is fully depend on cellular machinery on host for replication or protein synthesis.
🧬 Structure of Virus - Lecture Guide
- 01:33 - DNA and RNA in Viruses
- 02:18 - Infection in Plants (ssRNA)
- 03:46 - Capsid and Nucleoprotein Details
- 04:44 - Helical and Polyhedral Shapes
- 06:44 - Human Viral Diseases
- 07:18 - Viral Symptoms in Plants
00:00 - Introduction to Virus Structure
00:30 - Genetic Material vs Protein Coat
- Virus with genetic material single stranded RNA infect the plants.
- Mosaic formation, leaf curling or rolling, yellowing and vein clearing, dwarfism stunted growth are symptoms of virus infection.
- Virus with genetic material single stranded or double stranded RNA and double stranded DNA infect the animals.
- Mumps, small pox, herpes influenza are vital disease.
Comparison table of Virus , Viroids and Prions
| Feature | Virus | Viroids | Prions |
|---|---|---|---|
| Genetic Material | DNA or RNA | RNA only (Low weight) | No Genetic Material |
| Protein Coat | Present (Capsid) | Absent | Abnormal folded Protein |
| Size | Small | Smaller than Virus | Similar to Virus |
| Discovery | Beijerinck / Stanley | T.O. Diener (1971) | Stanley Prusiner |
Viroids -
- T. O. Denier discovered a new infectious agent in spindle tuber disease of potato.
- This agents is smaller than virus. It is devoid of protein coat but has free infectious RNA. Its RNA has low molecular weight.
🔬 Viroids, Prions & Lichen - Lecture Notes
00:29 - Viroids & Potato Spindle Tuber Disease
Prions -
- It has been found that certain neurological infectious disease is transmitted by folded protein.
- These infectious protein is called Prions. The size of prions are similar to virus.
- Bovine Spongiform encephalopathy or mad cow disease in cattle is caused by Prions. Cr Jacob disease in human is also caused by the its variants.
💡Read also to understand about the Kingdom Protista: Classification, Characteristics & 25 Important NEET MCQs
Conclusion
- In summary, while viruses, viroids, and prions are all sub-viral infectious agents, they differ significantly in their composition.
- Viruses contain either DNA or RNA with a protein coat, viroids consist only of free low-molecular-weight RNA, and prions are infectious proteins without any genetic material.
- Understanding these microscopic entities is crucial for mastering the 'Biological Classification' chapter in NEET Biology."
💡To understand the detail information about the Kingdom Monera: General Characters, Classification & NEET MCQs read my next detailed guide
🎯 NEET MULTIPLE CHOICE QUESTIONS
🔥 100% CHALLENGE
"Questions yahi se aayega... taiyari jeet ki!"
1.Which of the following statement is not correct.
A. Virus is non cellular structure, may found In form of crystal out the living cell.
B.Term virus has been taken from the word venom by Jenner.
C. Virus uses the system of host cell and start to replicate with in host cell
D. Virus are smaller than bacteria because they can pass bacteria proof filters.
Answer : B
2. Dmitri Ivanowsky discovered virus which were causing
A. Spindle tuber disease
B. Late blight of Potato
C. Loose smut of wheat.
D. Tobacco Mosaic disease.
Answer: D
3. M.W. Beijerinck used term "Contagium vivum fluidium" for
A. Infected fluid of virus
B. Naked genetic material
C. Infected protein coat.
D. Infected fluid exist in various disease.
Answer: A
4.Who of the following crystallises virus particle out side the living cell.
A. Louis Pasteur
B. M.W. Beijerinck
C. W.M. stanley
D. Dmitri Ivanowsky
Answer: C
5. How many statement is /are correct .
1. Virus is obligate parasite.
2. Viral protein coat is called capsomere which is made up of small unit capsid.
3. Capsomere are helically or polyhedral geometrically arranged.
4. Virus has both DNA and RNA.
5. Virus containing double stranded RNA generally causes disease in plants.
A. Two B. Four
C. Three D. Five
Answer: A
6. Virus that causes disease in animal including human have
A. Single stranded RNA
B. Double stranded RNA
C. Double stranded DNA
D. All of the above.
Answer : D
7. Virus that causes disease in plants have
A. Single stranded RNA
B. Double stranded RNA
C. Double stranded DNA
D. All of the above.
Answer : A
8. Which of the following pair of disease is not caused by the virus.
A. Pneumonia and Typhoid
B. Small pox and Herpes
C. Mumps and influenza
D. All of the above.
Answer: A
9. Consider the following symptoms in plants of viral disease and select the correct code;
1. Leaf curling
2. Leaf rolling
3. Vein clearing
4. Yellowing of leaf
A. 1,2 and 3
B. 2, 3 and 4
C. 1,3 and 4
D. 1, 2,3 and 4
Answer: D
10. Consider the following statement and select the correct code:
1. T.O. Dienier discovered viroids.
2. He discovered this infectious agent from spindle tuber disease of potato.
A. Only 1 B. Only 2
C. Neither 1 nor 2
D. Both 1 and 2
Answer: D
11. Which of the following statement is not correct for the viroids.
A. Viroids is smaller than virus.
B. It has infectious genetic material only
C. It is devoid of protein coat.
D. Its RNA has high molecular weight.
Answer: D
12. Which of the following infectious agent causes neurological diseases.
A. Virus B. Viroids
C. Prions D. Bacteria
Answer : C
13. Bovine Spongiform encephalopathy or mad cow disease in cattle is caused by
A. Bacteria B. Virus
C. Viroids D. None of the above
Answer: D
14. How many statement is / are correct.
1. Prions are folded infectious protein.
2. The size of prions is small than virus.
3. Prions has RNA or DNA.
4. Cr Jacob disease in human is caused by variant of prions.
A. One B. Two
C. Three D. Zero
Answer: B
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