Topic 6 complete Flashcards
how do microorganisms decompose dead matter?
they secrete enzymes that decompose the matter into small molecules that they can respire
when microorganisms respire what is released?
methane and carbon dioxide
what types of microorganisms are decomposers?
bacteria and fungi
what 5 things help determine time of death?
body temperature, forensic entomology, muscle contraction, extent of decomposition and stage of succession
what is the internal human body temperature?
37 degrees Celsius
what is algor mortis?
the process of the body cooling to match the temperature of the surroundings
how many degrees does body temperature drop per hour?
1.5-2
what 3 things can affect how quickly a body cools?
air temperature, clothing and body weight
what is rigor mortis?
the muscles of a dead body contracting and becoming stiff
when does rigor mortis occur?
4-6 hours after death
why does rigor mortis happen?
muscle cells become deprived of oxygen
anaerobic respiration takes place
lactic acid builds up and pH decreases
enzymes which produce ATP denature
bonds between myosin and actin remain fixed
what is forensic entomology?
the study of the body being quickly colonised by a variety of different insects
how can time of death be estimated using forensic entomology?
by identifying the type of insect present
flies after a few hours, beetles afterwards
blowfly eggs hatch 24 hours after being laid
what happens at hours- a few days after death?
cells and tissues broken down by bodies enzymes and bacteria
skin turns green
what happens a few days- a few weeks after death?
microorganisms decompose tissue and organs which produces methane- body bloats
skin blisters and falls off
what happens a few weeks after death?
tissues begin to liquify
what happens a few months- a few years after death?
only skeleton remains
what happens decades to centuries after death?
skeleton beings to disintegrate
what 2 things affect speed of decomposition?
temperature and oxygen availability
what are the stages of succession on the body?
bacteria decompose tissue
flies lay larvae
flies feed and make favourable conditions for beetles
body dies and flies leave
Beetles eventually leave
what is the minimum amount of DNA needed to run PCR?
one molecule
what are the 5 steps of DNA profiling?
obtain sample
PCR used to amply DNA
Fluorescent tag added
gel electrophoresis used to separate DNA
gel viewed under UV light
where can a sample of DNA be obtained from?
blood, saliva, skin, hair etc
why is ethanol added for DNA extraction?
DNA is insoluble in alcohols so forms a precipitate
what are the steps of PCR?
melt, anneal, extend
what happens during PCR melting?
reaction mixture of DNA, free nucleotides, primers and DNA polymerase set up
mixture heated to 95 degrees C to break H bonds
what are primers?
short pieces of DNA that are complementary to the bases at the start of the fragment you want
what is the role of primers?
have specific base sequence
bind to complementary bases of DNA to be amplified
therefore provide site for DNA polymerase to bind to
what is the enzyme used in PCR?
DNA dependant DNA taq polymerase- used due to high optimum temperature so doesn’t denature during melt (95 degrees)
what happened during PCR anneal?
mixture cooled to 50-65 degrees C so the primers can bind (anneal) to the strand
what happens during PCR extend?
mixture heated to 72 degrees C
(so Taq polymerase can work)
DNA polymerase lines up free nucleotides alongside each template strand
new strands are formed
what is the machine used in PCR?
thermocycler
how many strands are made in the first cycle of PCR?
1 strand (doubles each time)
why is a florescent tag added?
added to the DNA fragments so they can be viewed under uv light (in the practical we use stain)
why is gel electrophoresis used?
used to separate the DNA fragments by length
what are the steps of gel electrophoresis?
DNA is placed into well in gel
gel is covered with buffer solution that conducts electricity
current is passed through gel and DNA moves towards the positive anode
smallest moves furthest
what happens after gel electrophoresis?
gel is viewed under uv light
fragments are viewed as bands
can compare how closely related people are by comparing their brands
what are the 3 uses of DNA profiling?
seeing how closely related people are
can be used to prevent inbreeding in animals
can match people to evidence at crime scenes
give an example of when is DNA profiling used to compare how closely related people are
DNA profiling is used in a paternity test, the DNA of the child and the potential father are compared and if they have many bands in common they are closely related
how does DNA profiling prevent inbreeding?
the DNA of animals (and plants) are compared and the individuals which are the most genetically different are bred
What issues does inbreeding cause?
causes a smaller gene pool which reduces the populations ability to adapt
causes some individuals to inherit an accumulation of harmful recessive alleles which would have been masked by healthy dominant alleles
are bacteria prokaryotic or eukaryotic?
prokaryotic- no nucleus
do bacteria or viruses have a membrane?
bacteria
do bacteria or viruses have a cytoplasm?
bacteria
do bacteria or viruses have ribosomes?
bacteria
do bacteria or viruses have flagellum?
some but not all bacteria
do bacteria or viruses have DNA?
chromosomal and plasmids in bacteria, viruses RNA or DNA
do bacteria or viruses have capsids?
viruses
do bacteria or viruses have pili?
bacteria
do bacteria or viruses have a slime capsule?
bacteria
do bacteria or viruses have a cell wall?
bacteria
do bacteria or viruses have an envelope?
viruses
do bacteria or viruses have attachment proteins?
viruses
do bacteria or viruses have enzymes?
viruses
are viruses or bacteria smaller?
viruses
what is the function of flagellum?
rotate for movement
what is the function of pili?
help stick cells together and used in gene transfer
what is the function of the slime capsule?
helps protects the bacterium from immune system cells
what are the folds in the plasma membrane called?
mesosomes
what is the function of a cell wall?
supports the cell
what is the bacterial cell wall made of?
peptidoglycan
what size ribosomes do bacteria have?
70s (small)
what is the function of ribosomes?
produce proteins
where does the envelope of a virus come from?
stolen from the cell membrane of the previous host cell
what is the function of attachment proteins?
let the virus attach to a host cell
how do bacteria reproduce?
through binary fission
how does HIV replicate?
virus binds to CD4 receptor on T-helper cell using GP120
capsid released into the cell and releases RNA
reverse transcriptase viral RNA->DNA
integrase inserts viral DNA into host DNA
host replicates all DNA
protease assembles new viral particles which are released killing the T-helper cell
new viruses bud from the host cell into the blood stream where they can infect more cells
what is the latency period?
during initial infection of HIV person may experience flu-like symptoms, after this HIV drops to lower level and patient won’t experience any symptoms this is the latency period
how does HIV cause AIDS?
HIV causes T-helper cells to drop
people are classed as having AIDS when their T-Helper cell levels drop below a certain level
what are the steps after someone has AIDS?
T helper cell levels drop, B cells no longer activated, no antibodies produced, minor opportunistic infections, major and potentially deadly infections
what are the stages of a TB infection?
droplets containing bacteria are inhaled
phagocytes in the lungs take up bacteria
bacteria survive and replicate in the phagocytes
immune system seals off infected phagocytes in tubercles
bacteria in tubercles become dormant
bacteria eventually become reactivated and overcome the immune system
TB can also spread from the lungs to other organs and can lead to organ failure and death if untreated
what are the symptoms of TB?
cough, weight loss, chest pain, fever
why can the TB bacterium in the tubercles not be destroyed by the immune system?
because the bacterium are in phagocytes which have self antigens
what bacterium causes TB?
mycobacterium tuberculosis
what are the 4 routes pathogens take when entering the body?
broken skin- provides direct access to tissues and blood stream
the digestive system- when contaminated food and drink is consumed
the respiratory system- every time we inhale
mucosal surfaces- the lining of the body cavities
define pathogen
any organism that causes disease
what are the 5 barriers of the non-specific immune response?
skin, gut and skin flora, stomach acid, hairs, lysozyme
how does the skin and clotting prevent pathogens entering the body?
provides physical barrier, blood clots play important role by keeping cuts closed but pathogens may get in before clot develops
how do skin and gut flora prevent pathogens infecting the body?
compete with harmful pathogens- limit numbers and therefore their ability to infect the body
secrete chemicals which help to destroy pathogens
how does stomach acid prevent pathogens infecting the body?
creates an acidic environment which is unfavourable for many pathogens
how does lysozyme prevent pathogens infecting the body?
by damaging their cell walls which makes the bacteria burst open
define antigen
anything that causes an immune response
what type of protein is lysozyme?
globular
what is the first step of inflammation?
the blood clotting cascade
what is included in the non-specific immune response?
inflammation, lysosome action, interferon, and phagocytosis
what are the steps of inflammation?
mast cells secrete histamine, histamine stimulates responses- vasodilation to increase blood flow in capillaries, the permeability of capillary walls increases (so blood plasma can enter the tissue)
what releases histamines in the non-specific immune response?
damaged white blood cells and mast cells
what are the effects of histamine?
increase blood flow, permeability of capillaries increases, vasodilation occurs
define oedema
swelling
what are the 2 types of phagocytes?
neutrophils and macrophages
what are phagocytes?
white blood cells that engulf bacteria
what happens during phagocytosis?
phagocyte recognises antigen on pathogen as non-self, phagocytes cell membrane surrounds pathogen- engulfing it, material is enclosed in a vesicle/ phagocytic vacuole in the cytoplasm, lysosome fuses with vacuole releasing enzymes (including lysozme and protease) which breakdown/digest pathogen, phagocyte becomes an antigen presenting cell- this initiates specific immune response
what type of proteins are interferons?
globular proteins
what do interferons do?
inhibit protein synthesis which stops viral replication, activates specific immune response
what are the 2 types of antigens?
self and non-self
what are antigens used for?
cell-to-cell recognition
which type of antigen stimulates an immune response?
non-self
what are the 2 stages of the specific immune response?
the humoral response and the cell mediated response
what is the type of cytokine in the specific immune response?
interleukins
what cell produces antibodies?
B cells/ plasma cells
what chains are antibodies made of?
4 polypeptide chains- 2 heavy and 2 light
what are the different regions in antibodies?
each chain has a variable region (where the antigen binds) and a constant region
both the heavy chains also have a hinge region
what is the purpose of a hinge region on an antibody?
allows flexibility for the antigen binding site to be place at different angles when binding to an antigen
what type of bonds hold the polypeptide chains in antibodies together?
disulfide bridges
what are the 4 ways antibodies fight infections?
agglutinating pathogens- clumping pathogens together for easy phagocytosis
neutralising toxins- antibodies bind to toxins so toxins cannot affect host cells
prevent pathogen from binding to host cells- bind to antigen and block receptors
act as opsonins to tag the pathogen for phagocytosis
what are the 2 types of antibody?
membrane-bound or secreted
how are membrane-bound antibodies structurally different to secreted antibodies?
membrane bound have an extra section of protein that anchors them to the B cell
where are T cells made?
produced in bone marrow and mature in thymus gland
where are B cells made?
produced and mature in the bone marrow
which cells are involved in the humoral response?
macrophages, T helper cells, T memory cells, B cells, and plasma cells
which cells are involved in the cell mediated response?
body cells, T helper, T memory, T killer,
what are the steps of the cell mediated response?
infected body cell becomes APC, T helper binds to antigen, releases interleukins/cytokines, T helper becomes active and divides into T helper & T memory & T killer, T killer binds to infected body cell, produces perforin which perforates cell membrane and kills body cell (lysis), T memory stay in blood and can rapidly divide upon reinfection
what are the steps of the humoral response?
macrophage engulfs pathogen (phagocytosis), becomes APC, T helper binds and produces cytokines/interleukins, active T helper divides into active T helper & T memory, T memory stay in blood
B cell engulfs pathogen, becomes APC, active T helper binds, produces interleukins, activate B cell, B cell divides into B memory and plasma cells (antigen specific antibodies)
which immune response causes the production of antibodies?
the humoral response
what are the 4 types of immunity?
active natural, active artificial, passive artificial, passive natural
give an example of active natural immunity
when you become immune after catching a disease
give an example of active artificial immunity
when you create antibodies for an antigen from a vaccine
give an example of passive natural
antibodies in breast milk
give an example of passive artificial
immunity from a vaccine with antibodies
does active immunity give long or short term protection?
long term but takes a while for the protection to develop
does passive give long or short term protection?
short term but immediate
describe the pathogens used in vaccines
attenuated or dead
what are the 6 ways pathogens can evade the immune system?
- variation in antigenic properties (mutations)-HIV &influenza
- kill host cells they infect-HIV
- hide inside cells-TB
- hide inside genome- HIV
- preventing phagocytosis- TB
- prevent antigen presentation- HIV
what is the evolutionary arms race?
the battle between the vertebrates evolving mechanisms to deal with pathogens and the pathogens evolving ways of evading the host’s immune system
what are HIV’s evading mechanisms?
kills T Helper cells once its infected them to reduce number of cells which can detect the presents of the virus
has antigenic variability so memory cells for one strain will not recognise another
prevents infected cells from presenting antigens- difficult to recognise and destroy pathogens
what are TB’s evading mechanisms?
the bacteria produces substances which prevent lysosomes fusing with the phagocytic vesicle (bacteria can then multiply)
disrupts antigen presentation so difficult to recognise and destroy pathogens
what are the 2 types of antibiotics?
bacteriostatic and bactericidal
what do bacteriostatic antibiotics do?
slows the bacteria reproduction and control the population numbers
what do bactericidal antibiotics do?
kill bacteria
what are prophylactic antibiotics?
taken before a medical procedure to prevent risk of infection
what are the 4 ways antibiotics affect bacteria?
inhibit bacterial enzymes
bind to ribosomes to prevent protein synthesis
damage cell membranes
prevent bacterial DNA from coiling so it no longer fits in cell
why will eukaryotic cells not be affected by antibiotics?
they don’t have cell walls
they have different enzymes
they have different ribosomes
what is the advantage of broad spectrum antibiotics?
good if you don’t know what the bacteria is
what are the disadvantage of broad spectrum antibiotics?
will kill beneficial bacteria as well
expose lots of bacteria to the antibiotic and encourage more resistance
what are the advantages of narrow spectrum antibiotics?
less secondary infections
less bacteria exposed so less general resistance
doesnt kill benefical bacteria
what are the disadvantages of narrow spectrum antibiotics?
time and money spent identifying bacteria
what are narrow spectrum antibiotics?
antibiotics which are species specific
what are broad spectrum antibiotics?
kill lots of different types of bacteria
what should be done to stop HAIs spreading?
medical staff should wash hands between patients
equipment and bedding should be sterilised between uses
patients with HAIs should be isolated
staff should not wear long sleeves- bare below the elbows
what should be done to prevent antibiotic resistance spreading?
doctors shouldn’t prescribe antibiotics for minor infections
doctors shouldn’t prescribe antibiotics for prevention
use narrow-spectrum antibiotics whenever possible
rotate use of antibiotics
patients should finish full course of antibiotics
what are introns?
sections of DNA that don’t code for amino acids
during transcription what is copied into pre-mRNA?
both introns and exons
what is splicing?
introns are removed and exons are spliced together to form mRNA
what is alternative splicing?
sometimes some exons are removed (or spliced differently)- this produced more than one amino acid sequence from one gene and so more than one protein can be made from one gene
what are the 2 types of post transcriptional modification?
splicing and alternative splicing
