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L5 Structure and Function of viruses

Description

Objectives: describe the basic structural characteristics of viruses, compare the lytic and lysogenic replication cycles of bacteriophages, outline the replication cycles of mammalian cell viruses(naked and enveloped), describe the term viral latency in relation to the replication of bacterial and mammalian viruses.
Mer Scott
Quiz by Mer Scott, updated more than 1 year ago
Mer Scott
Created by Mer Scott about 7 years ago
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Resource summary

Question 1

Question
Which statement about viruses is NOT correct?
Answer
  • Viruses can multiply only by using a dividing host cell's machinery.
  • Viruses are ubiquitous.
  • Virus particles are called virions.
  • There is estimated to be around 2000 viruses which affect humans.

Question 2

Question
Which statements BEST describes viruses?
Answer
  • Viruses are a diverse group of acellular or 'sub-cellular' particles with no metabolic activity of their own, which rely on the biomachinery of their hosts to reproduce.
  • Viruses are very small non-living cells which hijack living cells in order to reproduce copies of themselves.
  • Viruses are ubiquitous 'sub-cellular' particles which rely on their hosts to reproduce.

Question 3

Question
The independent particles of viruses are called [blank_start]virions[blank_end], whose genetic material can be [blank_start]single[blank_end] or double stranded DNA or [blank_start]RNA[blank_end]. This is protected by a protein coat known as a [blank_start]capsid[blank_end]. Viruses with only a capsid are 'naked'. Viruses with an [blank_start]envelope of lipids[blank_end] around this protein coat are 'enveloped'. This envelope of lipids can sometimes have [blank_start]glycoprotein spikes[blank_end].
Answer
  • virions
  • single
  • RNA
  • capsid
  • envelope of lipids
  • glycoprotein spikes

Question 4

Question
Select the statements about viral capsids which are CORRECT.
Answer
  • Viral capsids are always symmetrical and made of repetitive structures.
  • Capsomers and protomers are the sub-units of capsids.
  • Protomers are made up of capsomers.
  • Capsids can be helical, icosahedral, or complex in shape.

Question 5

Question
Which order of the steps of the viral life cycle is CORRECT?
Answer
  • entry, attachment, synthesis, assembly, release
  • attachment, entry, assembly, synthesis, release
  • attachment, entry, synthesis, assembly, release

Question 6

Question
Lytic=virulent and lysogenic=latent.
Answer
  • True
  • False

Question 7

Question
Bacteriophages are the virions which have a capsid specialised to infect bacterial cells.
Answer
  • True
  • False

Question 8

Question
Which statement about bacteriophage replication types is INCORRECT?
Answer
  • Lysogenic cycles are temperate e.g. can kill the cell or live within it.
  • The lytic cycle ends in cell lysing.
  • The lytic cycle releases 10-20 virions.
  • Lytic and lysogenic cells both inject their DNA into the host cell in order to reproduce.

Question 9

Question
Which statement BEST describes a prophage?
Answer
  • A prophage is the phage genome of the bacteriophage, either integrated with the DNA of the Lysogen (bacterium) or floating free in its cytoplasm, able to produce a lytic phage.
  • A prophage is the inserted DNA from the bacteriophage which lives inside the host cell, known as the Lysogen.
  • The prophage lives in the Lysogen and can become a lytic phage.

Question 10

Question
Which statement is true?
Answer
  • Lytic insertion is followed by immediate degradation of host DNA while the lysogenic genome only becomes virulent when induction (environmental stress, UV irradiation) occurs.
  • Lytic insertion does not harm the host DNA until the final stage of the lytic cycle.

Question 11

Question
Retroviruses must use the host cell's machinery, and their own enzyme Reverse Transcriptase, to make DNA from their RNA. An example is HIV.
Answer
  • True
  • False

Question 12

Question
Naked viruses enter the cell via receptors (endocytosis). Enveloped viruses fuse their viral envelope with the host's membrane.
Answer
  • True
  • False

Question 13

Question
The provirus (DNA of enveloped virus in host genome) is virulent.
Answer
  • True
  • False
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