Cells: HIV and viruses Flashcards
What does HIV stand for
Human immunodeficiency virus
What does HIV progress to
AIDS
What does AIDS stand for
Acquired immune deficiency syndrome
What is AIDS
It is the late stage of HIV infection that occurs when the body’s immune system is badly damaged because of the virus
Outline the features of HIV
- 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
What cells do HIV infect and replicate in (and what does it act as)
- It infects and eventually kills helper T-cells, which acts as host cells for the virus
HIV infects helper T-cells, why is this a problem
- 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
When does HIV develop into AIDS
- When the helper-T cell numbers in their body reaches a critically low level
- When symptoms of their failing immune system starts to appear
What is the latency period
Period between initial invasion and replication of virus, virus is dormant, patient doesn’t show any symptoms (which could last for years)
What are the initial symptoms of AIDS
- Minor infections of mucous membranes
- Recurring respiratory infections
As AIDS progresses what are the symptoms
- Patients become more susceptible to more serious infections e.g chronic diarrhoea, severe bacterial infections and tuberculosis
What are the symptoms of late stages of AIDS
- Serious infections can be developed e.g toxoplasmosis of the brain (a parasite infection) and a fungal infection of the respiratory system
Is it the HIV virus that kills aids patients, explain why
- No, its the serious infections that kill AIDS patients
Why do serious infections kill AIDS patients
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
List the factors that affect the progression of HIV to AIDS and survival time with aids
- Existing infections
- The strain of HIV that hey are infected with
- Age
- Access to healthcare
Outline the stages of HIV repilcation
- 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
How do antibiotics work
- 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
Why is a HIV virus so hard to treat
- 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)
What are most antiviral drugs designed to target
The few enzyme-specific enzymes (enzymes that inly the virus uses) that exist
What treatments could be used for HIV (antiviral drugs)
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
Outline the best ways to control HIV infections within a population
- ## Reducing the spread
How can HIV be spread
- Unprotected sexual intercourse
- Through infected bodily fluids (e.g. blood from sharing contaminated needles)
Why may a person who has AIDS not die directly of AIDS
Immune system is so weak it cannot fight of other infections