Viral structure and functions

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Viral structure and functions

411-W6/7 - antibiotics + respiratory physiology/pathologies

411-W6/7 - antibiotics + respiratory physiology/pathologies

Bacterial structure and functions
Pneumonia: Clinical
Cell wall synthesis inhibitors: Penicillins
Cell wall synthesis inhibitors: Cephalosporins
DNA synthesis inhibitors: Fluoroquinolones
Protein synthesis inhibitors: Tetracyclines
Miscellaneous protein synthesis inhibitors
Mycobacterium tuberculosis (Tuberculosis)
Tuberculosis: Pathology review
Influenza virus
Adenovirus
Anatomy of the lungs and tracheobronchial tree
Anatomy of the diaphragm
Anatomy clinical correlates: Thoracic wall
Anatomy clinical correlates: Pleura and lungs
Trachea and bronchi histology
Bronchioles and alveoli histology
Lung volumes and capacities
Anatomic and physiologic dead space
Alveolar surface tension and surfactant
Compliance of lungs and chest wall
Combined pressure-volume curves for the lung and chest wall
Ventilation
Zones of pulmonary blood flow
Regulation of pulmonary blood flow
Pulmonary shunts
Ventilation-perfusion ratios and V/Q mismatch
Diffusion-limited and perfusion-limited gas exchange
Alveolar gas equation
Oxygen binding capacity and oxygen content
Oxygen-hemoglobin dissociation curve
Carbon dioxide transport in blood
Pneumonia: Pathology review
Pneumonia
Pleural effusion
Mechanisms of antibiotic resistance
Antituberculosis medications
Pneumothorax
Pneumothorax: Clinical
Pleural effusion, pneumothorax, hemothorax and atelectasis: Pathology review
Mycobacterium leprae
Viral structure and functions
Mycoplasma pneumoniae
Pneumocystis jirovecii (Pneumocystis pneumonia)
Protein synthesis inhibitors: Aminoglycosides
Airflow, pressure, and resistance
Reading a chest X-ray
Respiratory system anatomy and physiology
Emphysema
Asthma
Chronic bronchitis
Bronchiectasis
Lung cancer
Pulmonary embolism
Lung cancer: Clinical
Lung cancer and mesothelioma: Pathology review
Bronchodilators: Beta 2-agonists and muscarinic antagonists
Bronchodilators: Leukotriene antagonists and methylxanthines
Obstructive lung diseases: Pathology review
Cystic fibrosis
Alpha 1-antitrypsin deficiency
Law of Laplace

Assessments

USMLE® Step 1 questions

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Questions

USMLE® Step 1 style questions USMLE

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A group of researchers are studying the infectivity of certain viruses. In one part of the study, a purified viral genome is taken from a virus and injected into a host cell. It is noted that the purified viral genome induces replication of the genome and production of viral proteins in the host cell. This viral genome most likely belongs to which of the following viruses?  

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Viruses are a unique group of pathogens with a simple acellular organization and a distinct pattern of multiplication.

Despite their simple structure they are a major cause of disease.

They have no cytoplasmic membrane, cytosol, or functional organelles, but they can infect all types of cells, and numerous viruses can also infect bacteria, which are called bacteriophages.

Viruses and bacteriophages are not capable of metabolic activity on their own, so instead, they invade other cells and use their metabolic machinery to produce more viral molecules, nucleic acid and proteins which then assemble into new viruses.

Viruses can exist either extracellularly or intracellularly.

In the extracellular state, the virus is called a virion and isn’t capable of reproducing.

A virion consists of a protein coat, called a capsid, surrounding a nucleic acid core which contains the genetic material or the viral genome.

The nucleic acid and the capsid are collectively called a nucleocapsid.

Some virions have a phospholipid membrane derived from the host cell, called an envelope which surrounds the nucleocapsid.

The viruses that have an envelope are called enveloped viruses and these include the herpesviruses and HIV, while the ones that lack the envelope, such as poliovirus, are called non enveloped or naked viruses.

Once inside the cell, the virus enters the intracellular state, where the capsid is removed and the virus becomes active.

In this state the virus exists solely as nucleic acids that induce the host to synthesize viral components from which virions are assembled and eventually released.

Now, the viruses are surrounded by an outer protein coating called the capsid, which protects the viral genome and aids in its transfer between host cells.

Also, according to their capsid symmetry the viruses can come in many shapes and sizes.

There are three types of shapes: helical, icosahedral, and complex.

First, the helical viruses have a capsid with a central cavity or a hollow tube which is made by proteins arranged in a circular fashion, creating a disc like shape.

The disc shapes are attached helically, creating a tube with room for the nucleic acid in the middle.

An example of a virus with helical symmetry is the tobacco mosaic virus which is the most studied example.

Moving on to the icosahedral viruses which are made up of equilateral triangles fused together in a spherical shape that fully encloses the genetic material.

These viruses are released into the environment when the cell dies, breaks down and lyses, thus releasing the virions.

Summary

Viruses are a unique type of pathogen that lack cytoplasmic membrane, cytosol, or functional organelles and use the metabolic machinery of host cells to produce more viral molecules. They can exist extracellularly as a virion or intracellularly as nucleic acids that induce the host to synthesize viral components. Viruses come in many shapes and sizes, including helical, icosahedral, and complex. The viral genome can be DNA or RNA, single-stranded or double-stranded, and mutations in RNA viruses occur more frequently than in DNA viruses due to the likelihood of transcription errors by RNA polymerases.