Tag: Structure

Ribosome


Ribosome


Structure & functions:

→ Are small granules of RNA’s usually occurring in clusters called Polyribosomes.

→ Polyribosomes are attached to one mRNA molecule increasing its rate of polypeptide synthesis.

→ Hence, Ribosomes are “Actual site of Protein Synthesis”.

→ Types: Free Ribosomes (Present in Cytosol); Bound Polyribosome (Present embedded on Rough ER)

Peroxisome


Peroxisome


Structure & function:

→ Cellular storehouses of metabolic enzymes.

→ Matrix = Nearly 50 enzymes catalyzing various metabolic reactions.

→ Enzymes: Catalase & urate oxidase (Uric acid oxidase).

→ Function: Alcohol detoxification, H2O2 degradation (catalase) & other harmful compounds in Liver

→ Oxidation of long & very long chain fatty acids.

Mitochondria


Mitochondria


Structure & function:

→ Are spherical or cylindrical bodies with 2 lipid bilayer-protein membranes (Outer & Inner membrane)

→ Described as “Powerhouse of cell” – Presence of Enzymes for Energy metabolism & ATP synthesis.

→ Contains independent DNA apart from Nucleus.

→ Functions: Importing & self-synthesizing of Protein.

Metabolic pathways:

→ Fatty Acid Oxidation, Electron Transport Chain (ETC) & Krebs (TCA / Citric acid) cycle & Oxidative Phosphorylation.

→ Urea Cycle & Gluconeogenesis – Initial steps in Mitochondria  Later steps in Cytosol.

Mitochondrial enzymes:

Location Enzyme
Intra-crystal / Intra-membrane space
  • Creatine Kinase & Adenyl Kinase
Inner Membrane
  • Succinate Dehydrogenase & ATP synthase
Mitochondrial Matrix
  • Pyruvate & Glutamate Dehydrogenase.
  • For Citric Acid Cycle, β-Oxidation of Fatty acid, Urea Cycle

“MARKER ENZYMES” – Enzymes in Matrix, Inner Membrane & Inter-membrane space

Rotavirus : Classification, Structure, composition and properties

Rotavirus : Classification, Structure, composition and properties


Rotavirus

  • Family: Reoviridae
  • Genus: Rotavirus

Classification of Rotavirus:

  • Classified into seven distinct groups (A to G) based on structural antigen VP6.
  • Group A, B, and C Rotaviruses are found in Human infection as well as animal infection
  • Group A Rotaviruses are most frequent Human pathogen

Structure, composition and properties of Rotavirus

1. Structure:

  • Characteristics ”wheel” like appearance (Rota-means wheel)
  • Size: 65nm-100nm in diameter
  • Shape: Spherical shape
  • Symmetry: Icosahedral

2. Genome composition:

  • Genome: 11 segments of double-stranded RNA (ds RNA )
  • Can undergo genetic reassortment.
  • Protein: 6 structural protein (VP) and 6 Non-structural protein (NSP)
  • Envelope: Absent
  • Nucleic acid is surrounded by two layer of capsid- inner capsid (VP6) and outer capsid (VP7)
  • VP4 is the spike protein, it is a cell surface receptor

3. Other properties

  • Replication: Occurs in cytoplasm of infected cell.
  • Rotavirus contain an RNA-dependent RNA polymerase and other enzymes capable of producing capped RNA transcripts

Rotaviruses are inactivated by-

  • Heating to 100°C
  • Treatment with acid (pH<3),
  • Glutaraldehyde (3%),
  • Phenol,
  • Formalin,
  • Chlorine
  • Alcohol (70%) 

Replication of Rotavirus:

  1. Attachment: by VP4 on cell surface receptor
  2. Penetration: receptor-mediated endocytosis
  3. Un-coating in lysosome
  4. Transcription is mediated by endogenous virus dependent RNA polymerase (transcriptase)
  5. Translation to produce viral structural protein
  6. Synthesis of full-length transcript
  7. Some of the full-length transcript are encapsidate
  8. Synthesis of –ve sense RNA strand with capsid to form ds RNA
  9. Formation of inner capsid
  10. Morphogenesis: budding of single shelled virus into RER acquiring pseudo envelope
  11. Removal of pseudo envelope and replaced by outer capsid in RER
  12. Maturation
  13. Cell lysis and Release
Exam Question
 
  • Rotavirus is a double-stranded RNA virus belonging to the family Reoviridae.
  • Under electron microscope, Rotavirus looks like a wheel.
  • The RNA is enclosed in a triple layered, non enveloped icosahedral capsid.
  • It is one of the commonest cause of watery diarrhoea in children.
  • Oral rehydration therapy is the most appropriate treatment of choice.
  • Segmented genome is found in Rotavirus
  • One unique feature of rotaviruses is the ease with which the 11 RNA segments can undergo reassortment.
Don’t Forget to Solve all the previous Year Question asked on Rotavirus : Classification, Structure, composition and properties

Rotavirus : Classification, Structure, composition and properties

Rotavirus: Classification, Structure, composition and properties

Q. 1

Which of the following statement regarding Rota virus is false?

 A

Most commonly affects children

 B

Double stranded RNA virus

 C

It is a non enveloped virus

 D

None of the above

Q. 1

Which of the following statement regarding Rota virus is false?

 A

Most commonly affects children

 B

Double stranded RNA virus

 C

It is a non enveloped virus

 D

None of the above

Ans. D

Explanation:

Rota virus is a double stranded RNA virus belonging to the family Reoviridae.

The RNA is enclosed in a triple layered, non enveloped icosahedral capsid.

It is one of the commonest cause for watery diarrhoea in children.

Oral rehydration therapy is the most appropriate treatment of choice.


Q. 2

Reassortment has enabled the development of live vaccines, which is a feature of the following virus?

 A

Hepadna virus

 B

Herpes virus

 C

Astrovirus

 D

Rotavirus

Q. 2

Reassortment has enabled the development of live vaccines, which is a feature of the following virus?

 A

Hepadna virus

 B

Herpes virus

 C

Astrovirus

 D

Rotavirus

Ans. D

Explanation:

One unique feature of rotaviruses is the ease with which the 11 RNA segments can undergo reassortment.

Reassortment has enabled the development of live vaccines that combine genes from readily cultivated animal rotaviruses with human rotavirus genes that encode serotype-specific capsid proteins.

Ref: Ray C.G., Ryan K.J. (2010). Chapter 15. Viruses of Diarrhea. In C.G. Ray, K.J. Ryan (Eds), Sherris Medical Microbiology, 5e.


Q. 3

Segmented genome is found in – 

 A

Retrovirus

 B

Rotavirus

 C

Poliovirus

 D

Rhabdovirus

Q. 3

Segmented genome is found in – 

 A

Retrovirus

 B

Rotavirus

 C

Poliovirus

 D

Rhabdovirus

Ans. B

Explanation:

Ans. is b-  Rotavirus


Q. 4

Which of the following is true about Rotavirus ‑

 A

Commonly affects children

 B

Double Stranded DNA

 C

Can be grown easily on cell culture

 D

Egg shell appearance under electron microscope

Q. 4

Which of the following is true about Rotavirus ‑

 A

Commonly affects children

 B

Double Stranded DNA

 C

Can be grown easily on cell culture

 D

Egg shell appearance under electron microscope

Ans. A

Explanation:

Ans. is ‘a’ i.e., Commonly affects children 

.   Rotavirus are now recognized as the most common cause of diarrhea! disease in infants and children.

.  Rotavirus has double stranded RNA

.  Under electron microscope, Rotavirus looks like a wheel.


Q. 5

Genetic reassortment is seen with

 A

Astrovirus

 B

Herpes virus

 C

Rotavirus

 D

Hepadena virus

Q. 5

Genetic reassortment is seen with

 A

Astrovirus

 B

Herpes virus

 C

Rotavirus

 D

Hepadena virus

Ans. C

Explanation:

Ans. is ‘c’ i.e., Rotavirus 

  • The segmented genome of rotavirus allows genetic reassortment during coinfection – a property that may play a role in viral evolution and has been utilized in the development of reassortment animal – human rotavirus – based vaccines.

Q. 6

Double stranded RNA virus with segmented genome‑

 A

Influenza

 B

Rotavirus

 C

Arenavirus

 D

Bunyavirus

Q. 6

Double stranded RNA virus with segmented genome‑

 A

Influenza

 B

Rotavirus

 C

Arenavirus

 D

Bunyavirus

Ans. B

Explanation:

Ans. is ‘b’ i.e., Rotavirus


Q. 7

Double stranded RNA virus ‑

 A

Rotavirus

 B

Measles virus

 C

Mumps virus

 D

Influenza virus

Q. 7

Double stranded RNA virus ‑

 A

Rotavirus

 B

Measles virus

 C

Mumps virus

 D

Influenza virus

Ans. A

Explanation:

Ans. is ‘a’ i.e., Rotavirus



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