CELS 191 Lecture 32

Question 1

what are viruses

Answer 1

acellular microorganisms that cannot survive without a host - they have no metabolic activity of their own so they rely on the biosynthetic machinery of infected cells to multiply

Question 2

what are the most abundant biological entities on earth

Answer 2

viruses

Question 3

what are the components of viruses

Answer 3

genetic material - DNA or RNA
capsid - a protein coat the surrounds and protects the genetic material
sometimes…
envelope of lipids that surrounds the protein coat when they are outside a cell and facilitates entry into the cell

Question 4

what are viruses without an envelope called

Answer 4

naked (non-enveloped) viruses - viruses with envelopes are called enveloped viruses

Question 5

what are viral capsids composed of

Answer 5

multiple units of the same globular protein building block known as capsomeres - capsomeres are subunits of the capsid arranged in a precise and highly repetitive pattern around the nucleic acid

Question 6

what are the three types of symmetry that viral capsids can be arranged in

Answer 6

helical
icosahedral
complex

Question 7

what is an icosahedron

Answer 7

a 3D shape with 20 faces which are all equilateral triangles

Question 8

what is the structure of a complex virus

Answer 8

the head has icosahedral symmetry and the tail is helical

Question 9

how can viral genomes be arranged

Answer 9

linear
circular
segmented (like chromosomes)

Question 10

how big is a viral genome

Answer 10

sizes can vary from 4,000 to more than 1 million nucleotides - 3 genes to 100-1,000

Question 11

what do viruses infect

Answer 11

viruses infect all cell types as well as all forms of life

Question 12

what are bacteriophages

Answer 12

viruses that infect and replicate in bacteria

Question 13

what are the six stages of the lytic cycle

Answer 13

1. attach
2. penetrate
3. uncoat
4. genome replication and gene expression
5. assembly
6. release

Question 14

how do viruses attach to host cells

Answer 14

through receptors on the host cell

Question 15

how do genetic variants occur in viruses

Answer 15

viruses have limited proof reading mechanisms which leads to errors which generates variants and allows for tracking

Question 16

what is a spike on a virus

Answer 16

spikes are critical for attachment and cell entry - they are a major target for neutralising immunity

Question 17

was receptor does the SAR-CoV-2 virus attach to

Answer 17

ACE2