topic 6 Flashcards
state the role of micro organisms in breaking down organic matter and releasing carbon compounds into the atmosphere
micro organism such as bacteria and fungi are an important part of the carbon cycle
when plants and animals die, microorganism inside and on them will secrete enzymes that decompose dead organic matter into smaller molecules that they can respire
when micro organisms respire these small molecules, methane and CO2 are released
this then recycles CARBON back into the atmosphere
how can body temperature be used to determine the time of death
body temperature usually ranged between 67
as soon as an individual dies their body temperature starts to cool due to the absence of heat producing reactions
the environmental conditions need to be noted
the cooling of the body follows a sigmoid curve
body temperature is taken via the rectum or abdominal stab with a LONG thermometer
however the body temperature cn be affected by many factors such as
body size body position clothing air movement humidity temperature of the surroundings
how can rigorous mortis be used to determine the time of death
after death the muscle cells become starved of oxygen and oxygen dependant reactions stop
respiration in the cells becomes aerobic and produces lactic acid
the ph of the cell falls inhibiting the enzymes and therefore inhibiting aerobic respiration
the ATP needed for muscle contraction is no longer produced
and therefore actin and myosin become fixed ( they no longer slide over each other - sliding ligament theory)
smalle msucles stiffen faster than larger muscles
what occurs straight after death
autolysis - the cells and tissue begin to break down by the body’s enzymes and bacteria
putrefaction - this is when the skin begins to turn greenish due to the formation of sulfhaemoglobin
the micro organisms decompose tissues and organs, this produces gases such as methane which causes the body to bloat
the skin begins to blister and fall off
the tissues begin to liquefy and seep out into the areas around the body
how can forensic entomology be used to determine the time of death
the presence of insects allow forensic entomologists to make an estimate on how much time it has been since death
record the location and condition of the body and then take some sample of the insects found on near or under the body.
making sure to nite when and when each insect was foun
the temperature of the air, ground, body and maggot mass are measured in order that the rate of maggot development can be determined
some of the maggots will be taken back to the lab, where they will be fed and allowed to complete their development
this is useful for species identification and establishing when they pupate
for example blow flies
blow flies will find the body on the time of death
they will then lay their eggs a few days after death
it then goes through EGG, LARVA ( MAGGOT), THEN PUPATE
if a maggot is found on the body it is then back to the lab and fed till it finished its life course and then it is calculated from there ehrn the egg was laid
explain how the stages of succession can be used to determine the time of death
immediately after the time of death the conditions in the dead body are favourable for bacteria
as the bacteria decompose tissue, the conditions in the dead body become more favourable for flies and their large
when the large feed on a dead body, they ,are the conditions form favourable for beetles
as a dead body dries out the conditions become less favourable for flies and the beetles remain and decompose the dry tissue
after this it is no longer favourable for any organism
what are the non specific responses to infection
interferon
phagocytosis
inflammation
what are the steps of phagocytosis
a phagocyte recognises the antigen on a pathogen
the cytoplasm of the phagocyte moves round the pathogen engulfing it
the pathogen is now contained in the phagocytic vacuole in the cytoplasm of the phagocyte
a lysosome ( an organelle which contains digestive enzymes lysozymes) fuses with the phagocytic vacuolee
the lysozyme then break down the pathogen
the phagocyte then presents the pathogen’s antigens ( it becomes an antigen presenting cell)
this will then initiate the specific response to infection
macrophages can also act as phagocytes
what is interferon used for
when cells are infected with VIRUSES they produce the PROTEIN interferon
interferon is Iseo to prevent viruses from spreading to uninfected cells
this is done through
preventing viral replication, by inhibiting the production of viral proteins
they activate the cells involved in the specific immune response to kill infected cells
they activate other mechanism of non specific response for example they promote inflammation
what is the process of inflammation
- the immune system cells recognise foreign antigens on the surface of the pathogen and release histamine that trigger inflammation
- histamine cause vasodilation ( widening of blood vessels) of the arterioles increasing blood flow of the capillaries to the site of the infection
- it also increases the permeability of the capillaries this allows white blood cells and antibodies leak from the blood to the tissue, causing them to be attacked by the white blood cells
outline the specific response to infection
- the macrophage becomes antigen presenting
- they bind to the t helper cells
- this activates the t helper cells which causes them do dived by mitosis
- the activated t helper cells then bind to the antigen presenting cells
- the results in the release of cytokines
- this causes colonial expansion of the B cells as well as the activation of t killer cells
- the B cells will then differentiate into b memory and b effector cells
- through further differentiation they will differentiate into plasma cells
- the plasma cells will produce antibodies
describe the structure of antibodies
antibodies are made from 4 polypeptide chain; two heavy chains and two light chains
each of these chains has a variable region and a constant region
the variable regions of the antibody form the antigen binding sight
the shape of the variable regions are complimentary to a particular antigen, the variable region differs between antibodies
the hinge region allows flexibility when the antibody binds to the antigen
the constant region allow binding to the receptors on the phagocytes and macrophages (this region is the same for all antibodies)
disulphide bridges hold the polypeptide chains together
how to antibodies help to clear infections
- agglutinating pathogen - the pathogens are clumped together to make phagocytosis easier
- opsonisation - the pathogens are marked for phagocytosis
- neutralisation - neutralisation of harmful toxins
- lysis - breaking down of bacterial cells
describe the structure of a virus
viruses are non living, which contain either DNA or RNA (they can either be single or double stranded) enclosed in a capsid. it is sometimes covered in a lipid envelope ( from the cell membrane - phospholipid bi layer of the host cell)
in the HIV virus they have the same structure but they contain REVERSE TRANSCRIPTASE and DNA INTERGRASE
describe the structure of bacteria
the Dan of bacteria exists in the cytoplasm, it can also exist as plasmids
they contain ribosomes
they have a cell wall
and they have a plasma membrane
