Cells: HIV and viruses

Question 1

What does HIV stand for

Answer 1

Human immunodeficiency virus

Question 2

What does HIV progress to

Answer 2

AIDS

Question 3

What does AIDS stand for

Answer 3

Acquired immune deficiency syndrome

Question 4

What is AIDS

Answer 4

It is the late stage of HIV infection that occurs when the body’s immune system is badly damaged because of the virus

Question 5

Outline the features of HIV

Answer 5

• Core - contains genetic material (RNA) and some proteins (including enzyme reverse transcriptase)
• Capsid - protein shell of the virus protecting the RNA w/in it
• Reverse transcriptase - produces a DNA copy of the viral RNA, which is inserted into the chromosomes of the cell - allowing it to copy the viral DNA
• Envelope - made from the membrane stolen from the previous host cell
• Attachment proteins (glycoproteins) - allow the HIV to attach to the host helper T-cell

Question 6

What cells do HIV infect and replicate in (and what does it act as)

Answer 6

• It infects and eventually kills helper T-cells, which acts as host cells for the virus

Question 7

HIV infects helper T-cells, why is this a problem

Answer 7

• Helper T-cells send chemical signals that activate phagocytes, cytotoxic T-cells and B-cells
• When a person is infected with HIV, the virus enters is RNA into helper T-cells to make copies of itself causing the helper T-cells to die
• W/o enough helper T-cells, the immune system is disrupted and unable to effectively respond to infections because other immune system cells receive as much chemical signals from the T-cells

Question 8

When does HIV develop into AIDS

Answer 8

• When the helper-T cell numbers in their body reaches a critically low level
• When symptoms of their failing immune system starts to appear

Question 9

What is the latency period

Answer 9

Period between initial invasion and replication of virus, virus is dormant, patient doesn’t show any symptoms (which could last for years)

Question 10

What are the initial symptoms of AIDS

Answer 10

• Minor infections of mucous membranes
• Recurring respiratory infections

Question 11

As AIDS progresses what are the symptoms

Answer 11

• Patients become more susceptible to more serious infections e.g chronic diarrhoea, severe bacterial infections and tuberculosis

Question 12

What are the symptoms of late stages of AIDS

Answer 12

• Serious infections can be developed e.g toxoplasmosis of the brain (a parasite infection) and a fungal infection of the respiratory system

Question 13

Is it the HIV virus that kills aids patients, explain why

Answer 13

• No, its the serious infections that kill AIDS patients

Question 14

Why do serious infections kill AIDS patients

Answer 14

As aids progresses the patients get a very low number of immune system cells during the late stages of aids, which make them more susceptible to serious infections

Question 15

List the factors that affect the progression of HIV to AIDS and survival time with aids

Answer 15

• Existing infections
• The strain of HIV that hey are infected with
• Age
• Access to healthcare

Question 16

Outline the stages of HIV repilcation

Answer 16

• Attachment proteins on HIV attaches to a receptor molecule of the host helper T-cell
• The capsid of the HIV is released into the cell, where it uncoats and releases the RNA into the cells cytoplasm
• Inside the helper T-cell reverse transcriptase is used to make a complementary strand of DNA from the viral RNA AND from this a double-stranded DNA is made and inserted into the human DNA
• Host cell enzymes are then used to make viral proteins from the viral DNA found within the human DNA
• The viral proteins are the assembles into new viruses, which go on to infect other cells

Question 17

How do antibiotics work

Answer 17

• They kill bacteria by interfering with their metabolic reactions and target the bacterial enzymes and ribosomes used in these reactions
• They only target human enzymes and ribosomes so they don’t damage human cells

Question 18

Why is a HIV virus so hard to treat

Answer 18

• Viruses don’t have their own enzymes and ribosomes as they use the ones in the host’s cells to replicate AND antibiotics cant inhibit them because they don’t target human processes
• HIV has a high mutation rate, difficult to create treatment that’ll work as become resistant so quickly (can’t use vaccine)

Question 19

What are most antiviral drugs designed to target

Answer 19

The few enzyme-specific enzymes (enzymes that inly the virus uses) that exist

Question 20

What treatments could be used for HIV (antiviral drugs)

Answer 20

Drugs that target viral enzymes e.g. reverse transcriptase which the HIV makes (human cells do not make this enzyme), so no side effects on the body

Question 20

Outline the best ways to control HIV infections within a population

Answer 20

• ## Reducing the spread

Question 21

How can HIV be spread

Answer 21

• Unprotected sexual intercourse
• Through infected bodily fluids (e.g. blood from sharing contaminated needles)

Question 22

Why may a person who has AIDS not die directly of AIDS

Answer 22

Immune system is so weak it cannot fight of other infections