Immunity, forensics and infection Flashcards
what is a pathogen?
a microorganism that can cause disease
name 3 ways to determine how old a corpse is?
- rigamortis stage
- presence of species
- body temperature
what is in the core of a virus?
nucleic acid
what is a virion?
virus before it enters the host cell
what is a capsid?
protien coat of a virus
what surrounds a capsid on a large virus?
an envelope
which type of nucleic acid in a virus is more dangerous and why?
RNA, as it mutates much more
what do spike protiens do?
help the virus to attach to specific receptors on the host cell
how many ways of viral entry are there?
2
describe both methods of viral entry?
- virus injects nucleic acid into cell
- plasma membrane of host cell surrounds virus and produces a virus filled vacuole in cytoplasm, the virus bursts out, releasing nucleic acid
what are introns?
non-coding regions of DNA, used in DNA profiling
what is satellite DNA?
large arrays of repeating, non-coding DNA
what does PCR do?
amplifies DNA sample
what 5 things does PCR require?
- target DNA
- primers
- DNA polymerase
- free nucleotides
- buffer solution
what are the 3 stages of PCR?
- denaturation
- annealing
- elongation/extension
describe the PCR stage denaturation?
DNA is heated to 95C to break hydrogen bonds
describe the PCR stage annealing?
temperature decreased to 50-60C so primers can anneal to the ends of single stranded DNA
describe the PCR stage elongation/extension?
temperature increased to 72C for 1 minute, this is the optimum temperature for taq polymerase to build complementary DNA strands
name 4 features of bacteria?
- no membrane bound organelles
- no nucleus
- genetic material in cytoplasm
- cell wall + membrane
- ribosomes
what do primary defences do?
stop pathogens entering the body
are primary defences specific?
no
name 4 primary defences?
- stomach acid
- gut flora
- inflamation
- mucus
how does inflamation stop pathogens?
vasodilation increases permeability of blood vessels, so more white blood cells can enter
name 3 ways the skin is adapted as a primary defence?
- strengthened by keratin
- covered by flora
- antimicrobial secretions
where can tuberculosis affect?
mainly lungs, can be kidney spine and brain
what type of phagocyte engulf tuberculosis bacteria?
macrophage
how can tuberculosis bacteria survive macrophages?
- overpower and encase macrophage in tubercles
- stops formation of lysosomes
what are the 3 stages of tuberculosis infection?
- primary infection
- latent infection
- active disease
is HIV RNA or DNA?
RNA
describe the 4 stages of HIV replication?
- Virus enters T helper cells by attaching to a CD4 receptor
- reverse transcriptase enzyme produces a complementary RNA strand
- virus uses host cells enzymes to make new viral components
- Host cell lyses, viruses enter the blood, cycle repeats
name the 3 stages of HIV infection?
1 - accute HIV syndrome
2 - Chronic or asymptomatic stage
3 - advanced AIDS
how does HIV avoid antibodies?
- frequently mutates, to change antibodies
- uses host cell plasma membranes to hide antigens
what is the lymphatic system responsible for?
complex transport of immune cells
name the 2 types of phagocyte?
- neutrophyls
- macrophages
name 3 features of neutrophylls?
- most common phagocyte
- made in bone marrow
- short acting, for immediate response
name 3 features of macrophages?
- biggest phagocyte
- made in bone marrow
- adaptive, specific immune response
name the 5 stages of phagocytosis?
1 - detects pathogen by unique antigen and recognises by its pathogen recognition receptors on cell membrane
2 - phagocyte activates, pathogen is covered in opsinins, helps to bind
3 - engulfs, encases in phagosome
4 - phagosome fuses with lysosome, lysozyme breaks down pathogen
5 - phagocyte absorbs products, some products are discarded, some are used in the antigen presentation process to activate T-helper cells
define antibody?
glycoprotien with specific antigen binding site
name 2 ways antibodies kill pathogens?
- agglutination
- neutralising the toxins they produce
where do B cells form?
bone marrow
where do T cells mature?
thymus
what are the 2 specific immune responses?
- cell mediated immunity
- humoral immunity
what type of pathogen does cell mediated immunity mainly affect?
viruses
describe the 4 steps of the cell mediated response?
1) Macrophages engulf and digest pathogens, presenting their antigens
2) Specific T helper cells with complementary receptors bind
3) T helper cell produces interloukins
4) Cloned T cells may become T killer, T memory or T helper cells
define antigen?
specific protiens on every cells surface
describe the 4 steps of the humoral response?
1) T helper cells bind to antigens on presenting b cells
2) T helper cells produce interloukins
3) B cells divide rapidly into plasma and memory cells
4) Plasma cells produce antibodies to bind to and kill pathogens
what type of pathogen does the humoral response affect?
bacteria and fungal
what happens after a B cell engulfs a pathogen?
presents antigens, becoming an antigen presenting cell
what are the 2 types of antibiotics?
- bactericidal
- bacteriostatic
what do bactericidal antibiotics do?
kill bacteria
what do bacteriostatic antibiotics do?
slow bacterial growth and reproduction
name 4 ways antibiotics can affect bacteria?
- inhibit cell wall synthesis
- inhibit DNA synthesis
- disrupt cell membrane
- disrupt protien synthesis
- inhibit metabolic enzymes
what is MRSA?
causes wound infections
what is clostridium difficile?
- infects digestive system
- when gut flora is killed by antibiotics, it can colonise
name 3 ways hospitals prevent superbugs?
- hand hygiene
- isolations
- stricter prescriptions
