6.2.1 - Structure Of Bacteria & Viruses Flashcards
What Are Bacteria?
Small, single-celled prokaryotes.
What Features Do Bacterial Cells Have?
(9 Points)
~ Flagellum.
~ Ribosomes.
~ Cell wall.
~ Plasma / Cell membrane.
~ Capsule.
~ Plasmids.
~ Bacterial chromosome.
~ Pili.
~ Cytoplasm.
What Are Viruses?
(2 Points)
~ Microorganisms, made of nucleic acids (DNA and RNA) surrounded by a protein.
~ Non-cellular infectious particles.
What Is The Relative Size And Complexity Of Viruses Compared To Prokaryotic Cells?
Smaller and structurally simpler than prokaryotic cells.
What Cellular Structures Do Viruses Lack?
(3 Points)
~ Plasma membrane.
~ Cytoplasm.
~ Ribosomes.
What Components Make Up A Virus?
(5 Points)
~ Nucleic acid core.
~ Capsid.
~ Envelope.
~ Attachment proteins.
~ Proteins inside the capsid.
Viruses Have A ‘Nucleic Acid Core’, What Is Meant By This?
(2 Points)
~ Contains either DNA or RNA.
~ Can be single or double stranded.
Viruses Have A ‘Capsid’, What Is Meant By This?
Protein coat, protecting the genetic information of the virus.
Viruses Have An ‘Envelope’, What Is Meant By This?
(2 Points)
~ Extra outer layer.
~ Made from membrane-phospholipids of the host cell.
Viruses Have ‘Attachment Proteins’, What Is Meant By This?
(3 Points)
~ GP120.
~ Stick out from the edge of the capsid or envelope.
~ Allows the virus to attach to a host cells CD4 receptors.
Viruses Have A ‘Proteins Inside The Capsid’, What Is An Examples Of This?
E.g. HIV has an enzyme called reverse transcriptase, that converts RNA -> DNA once it has infected a cell.
What Can’t Viruses Survive Without?
Host cell.
How Do Viruses Reproduce?
Infect living cells and use their components responsible for synthesising proteins to create new viral particles.
What Is A Pathogen?
Any organism that causes disease.
What Are Infectious Diseases?
Ones which are caused by pathogens.
What Are Examples Of Pathogenic Microorganisms?
(3 Points)
~ Bacteria.
~ Fungi.
~ All viruses.
What Does ‘HIV’ Stand For?
Human immunodeficiency virus.
What Does HIV Do?
Infects and destroys T helper cells, which then acts as a host cell for the virus.
What Type Of Virus Is HIV?
Retrovirus.
How Is HIV Spread?
Through bodily fluids.
Where Does HIV Replicate?
Inside the T helper cells.
Describe The Process Of HIV Replication
(6 Points)
~ Attachment proteins (GP120) attaches to a receptor molecule (CD4) on the cell membrane of the host T helper cell.
~ Capsid is released into the cell, where it uncoats and releases RNA into the cells cytoplasm.
~ Inside the cell, reverse transcriptase is used to make a complementary strand of DNA from the viral RNA template.
~ From this a double-stranded DNA molecule is made and inserted into the hosts DNA.
~ The hosts cell enzymes are used to make viral proteins from the viral DNA found within the human DNA
~ The viral proteins are assembled into new viruses, which bud from the cell and go on to infect T helper cells.
What Will The Person With HIV Feel DURING The Initial Infection Period Of HIV?
Experience flu-like symptoms.
What Happens AFTER The Initial Infection Period Of HIV?
(2 Points)
~ Replication drops.
~ Latency period occurs.
What Happens During The Latency Period Of HIV?
The infected person won’t experience any symptoms, often for years.
What Does HIV Gradually Reduce?
The number of T helper cells in the immune system.
If There Is A Low Number Of T Helper Cells In The Immune System What Is No Longer Activated Or Produced?
(2 Points)
~ B cells are no longer activated.
~ No antibodies are therefore produced.
What Does HIV Lead To?
AIDS.
What Does ‘AIDS’ Stand For?
Acquired immune deficiency syndrome.
What Is AIDS?
A condition where the immune system deteriorates and eventually fails.
What Does AIDS Lead To?
Opportunistic infections.
What Are Opportunistic Infections?
(2 Points)
~ Diseases and infections that wouldn’t cause serious problems in people with a healthy immune system.
~ E.g. TB.
When Will A HIV Infection Progress To AIDS?
(2 Points)
~ When an individual starts to suffer from constant opportunistic infections.
~ When the T helper cell count drops below a critical level.
Describe How AIDS Progresses Through A Sequence Of Symptoms
(4 Points)
~ The initial symptoms of AIDS include minor infections of mucous membranes and reoccurring respiratory infections, which is caused by a lower than normal number of T helper cells.
~ As AIDS progresses the number of T helper cells decreases further, patients become more susceptible to more serious infections.
~ During the final stages of AIDS a person will suffer from a range of more serious opportunistic infections, due to a very low number of T helper cells.
~ It is these opportunistic infections that kill AIDS patients.
What Factors Affect How Quickly HIV Will Progress Into AIDS And How Long A Person With AIDS Will Survive?
(4 Points)
~ Number of existing infections.
~ The strain of HIV the person is infected with.
~ Age.
~ Access to healthcare.
What Causes Tuberculosis (TB)?
Mycobacterium tuberculosis.
How Does A Person Become Infected With TB?
(6 Points)
~ When tiny droplets containing the bacteria are inhaled into the lungs, inhaled from an infected persons cough or sneeze.
~ TB bacteria once in the lungs is engulfed by phagocytes, where it survives and reproduces.
~ Overtime the infected phagocytes become encased in tubercles in the lungs, where the bacteria will remain dormant.
~ The infected person shows no obvious symptoms at this point.
~ Later the dormant bacteria may become reactivated and overcome the immune system, usually done when the immune system is compromised and weakened.
~ The person will then develop TB, which varies between individuals.
