Unit One: Viruses

Question 1

What are Viruses?

Answer 1

• Non living
• Reproduce through host
• Obligate parasites(can’t function without a host)
• Smaller than most cells
• Around 10 to 400 nm
• Infectious particle consisting of a nucleic acid

Question 2

Examples of viruses are?

Answer 2

Covid-19, HIV, Herpes, Mono, Chickenpox

Question 3

Why are viruses considered non living?

Answer 3

• Unable to reproduce on their own
• Unable to move on their own
• Do not react to stimuli
• Don’t need energy and don’t metabolize

Question 4

Can any virus have any living thing as a host?

Answer 4

No. SOme viruses only infect one species where as others can infect a wide range.
The protine receptors on the virus must match the receptors on the host cell.

Question 5

What do all viruses consist of?

Answer 5

• Genetic info(DNA or RNA)
• Capsid(protine protective coat)

Question 6

How do we classify viruses?

Answer 6

• Size and shape of capsid
• Shape and structure of virus
• Genetic info(DNA OR RNA)
• Types of diseases they can cause

Question 7

What are the four shapes of viruses?

Answer 7

• Helical(Tobbaco Mosaic)
• Polyhedral(Adenovirus
• Spherical with envelopes(HIV)
• Head and tail(Bacteriophages)

Question 8

What are Bacteriophages?

Answer 8

• Known as phages
• Infect bacteria cells
• Do NOT enter the cell unlike most other viruses
• Inject DNA or RNA into host cell
• Capsid stays on the outside

Question 9

Differance between DNA viruses and RNA viruses?

Answer 9

DNA viruses have single or double strand DNA with capsid. i.e. herpes and mono
RNA viruses have single strand RNA with capsid. i.e HIV and ebola

Question 10

What are the two virus reproduction cycles?

Answer 10

Lysogenic cycle(asleep) and Lytic cycle(awake)

Question 11

What is the Lysogenic Cycle?

Answer 11

The Lysogenic cycle is when the virus inhabits a host cell and reproduces while staying dormant, meaning that the virus will no affect any normal functions. The virus first injects its genetic material into the host cells chromosomes. In this state it is refered to as a provirus. The provirus then replicates through the host cells reproduction. The virus can enter the lytic, or active, state through stress, infections or UV lights.

Question 12

What is the Lytic cycle and its steps?

Answer 12

Step one: Attatchment to receptor cite - Protines in virus tail specifically fit the structure of the cell walls/membrane.
Step two: Penetration - the virus injects genetic material and infects host cell, “hijaking” it.
Step three: Multiplication - the virus breaks up DNA of the host cell and produces copies of viral genetic material and protine capsids.
Step four: Assembly - viral genetic material and capsids are assembled into more viruses.
Step five: Lysis - the cell bursts and dies, realeasing viruses that infect neighboring cells.

Question 13

How are viruses transmitted?

Answer 13

Oral-transmission
Trans-placental(birth)
Sexual transmission
Animal or insect bites
Droplets(sneezing and coughing)
Direct inoculation(vaccines)

Question 14

Why are viruses bad?

Answer 14

• Infect animals, plants and humans
• Causes many diseases
• Can destroy cells and tissue
• Can hide in organisms, transmitting them unkowingly(lysogenic cycle)
• Can mutate and change appearance, making them harder to treat.

Question 15

Why are viruses good?

Answer 15

Genetic therapy - Viruses can be used to deliver drugs or genes to target cells. This can also be used to create genetically modified plants and organisms.
They can also be used to deliver chemotherapy drugs to cancerous cells.

Question 16

How are viruses “treated”?

Answer 16

Viruses cannot be killed as they are not alive and antibiotics don’t work on them. They can be avoided through vaccination.

Question 17

How do vaccines work?

Answer 17

Vaccines work by adapting our immune system and antibodies to certain viruses, using weak virus particles. This allows our white blood cells to recognize the virus faster and prevent it from harming the body.