paper one Flashcards
protein primary structure
the sequence of amino acids in a polypeptide chain
protein secondary structure
sequence of aa’s causes parts of proteins to bend into alpha helix or fold into B pleated sheets.
H bonds form between carboxyl groups of 1 aa and amino group of another.
protein tertiary structure
1) the further folding of the secondary structure
2) to create a unique 3D structure
3) held in place by hydrogen, ionicand disulfide bonds
quaternary structure
when a protein consists of 2 or more polypeptide chains
competitive inhibitors
bind to active site
prevents substrate from binding and reaction from occuring
if more substrate added- will out compete inhibitor
non competitive inhibitor
binds at allosteric site
causes active site to permanently change shape
substrate can no longer bind regardless of how much substrate is added
test for reducing sugars
1) add benedicts reagent to sample
2) heat in h2o bath for 5 mins
3) if brick red precipitate observed- reducing sugars present
4) if remains blue- not present
test for non reducing sugars
1) do reducing sugars to get negative test result
2) take fresh sample and add dilute acid (hydrochloric) and boil (hydrolyses it)
3) neutralise w an alkili and test w PH paper
4) add benedicts and heat again
5) if non reducing sugars present - brick red precipitate, if not- blue
test for starch
1) add iodine
2) if present- blue/black, if not- remain orange
test for protein
1) add buiret reagent to sample
2) if protein present- purple, if not- blue
test for lipids
1) add ethanol to sample and shake (dissolves sample)
2) add dissolved h2o and shake
3)if present- white emulsion
4 stages of semi conservative DNA replication
1) DNA helicase breaks H bonds between complementary base pairs between 2 strands causing double helix to unwind
2) seperated parental DNA strand acts as template. free floating DNA nucleotides within nucleus attracted to their complementary base pairs on template strands
3) nucleotides joined forming phosphodiester bonds by condensatio reaction catalysed by DNA polymerase
4) 2 sets of daughter DNA contains 1 strand of parental DNA and 1 newly synthesised strand.
ultracentrifugation
after homogenate solution is filtered:
1) supernate after 1st spin at low speed - pellet contains nuclei
2) 2nd spin at medium speed- pellet contains mitochondria and chloroplasts
3) 3rd spin at high speed - pellet contains lysosomes and SER/RER
4) 4th spin at v high speed- pellet contains ribosomes
cell cycle
1) interphase- when organelle duplicate, cells grow and DNA replicates
2) nuclear division- either mitosis (creates cells w identical DNA for growth and repair) or meiosis (creates gametes)
3) cytokinesis- division of cytoplasm to create new daughter cells)
prophase
chromosomes decondense and become visible, nuclear envelope breaks down
metaphase
chromosomes align along equator
spindle fibres attach to centromere and chromatid
anaphase
spindle fibres retract
chromatid are pulled to opposite poles
require atp
telophase
chromosomes become longer and thinner
spindle fibres break down
nucleus starts to reform
diffusion
net movement of molecules from an area of higher conc to an area of low conc until equilibrium is reached
facilitated diffusion
uses protein channels and carrier proteins
protein channels: form tubes filled w h2o- enables h2o soluble ions to pass through membrane
carrier proteins: will bind w molecule (e.g. glucose) which causes change in shape- enables molecules to be released to other side of membrane
osmosis
net movement of h2o from an area of high water potential to an area of lower water potential across a partially permeable mebrane
what is active transport
the movement of molecules and ions from an area of lower conc to an area of higher conc against conc gradient using atp and carrier proteins
how is atp and carrier proteins used in active transport
atp binds to protein on inside of membrane and is hydrolysed into adp and pi
this causes protein to change shape and open towards inside of membrane
causes molecule to be released on other side of membrane
pi molecule then released from protein- results in protein reverting to its original shape
contransport of glucose and amino acids process
sodium ions actively transported out the epithelial cell into blood in capillary
this reduces sodium ion conc of epithelial cell
sodium ions can then diffuse from lumen down the conc gradient into epithelial cell
sodium ions diffuse through contransporter potein so either glucose/aas also attach and are transported int epithelial cell against conc gradient
glucose moves from epithelial to blood by facilitated diffusion
phagocyosis process
pathogen releases chemoattractants that attract phagocyte
phagocytes attach to antigens on pathogen via receptor binding points on phagocyte
phagocyte changes shape to move around and engulf pathogen
once engulfed, pathogen contained with a phagosome vesicle
lysosome within the phagocyte fuses with the phagosome and releases its contents
lysozyme is released into phagosome which hydrolyses pathogen
pathogen destroyed- soluble products absorbed and used by phagocytes
what is the cell mediated response
when t cells only respond to antigens which are presented on cells and not antigens detached from cells and within body fluids (e.g. blood)
cell mediated response process
after phagocytosis, antigens presented on cell surface membrane
helper t cells attach to these antigens via receptors on their surface
once attached - activates t helper cells to divide by mitosis to replicate and make large numbers of clones
cloned helper t cells differentiate:
some remain as helper ts and activate b lymphocytes
some stimulate macrophages to perform more phagocytosis
some become memory cells for that shaped antigen
somebecome cytotoxic t cells
what is the humoral response
response involving b cells and antibodies
antibodies soluble and transported in bodily fluids
b cell activation
antigens in blood collide with complementary antibodies on b cell
b cell takes in atigen by endocytosis and presents on cell surface membrane
when this b cell collides with helper t cell receptor- activates b cell to undergo clonal expansion and differentiate
b cells undergo mitosis - differentiate into plasma and memory cells
plasma makes abs
b memory cells divide rapidly into plasma when reinfected with same pathogen
what is agglutination
when abs are flexible and can bind to multiple antigens to clump them together
makes it easier for phagocytes to locate and destroy pathogens
passive immunity
Abs introduced into body
pathogen doesnt enter body so plasms and memory cells not made
no long term immunity
e.g. abs passed to foetus through placenta
active immunity
immunity created by own immune system following exposure to pathogen/ its antigen
2 types:
natural
artificial
natural active immunity
following infection and creation of bodys own abs and memory cells
artificial active immunity
following introduction of weakened version of pathogen/antigen via vaccine
vaccine process
1) small amounts of weakened/ dead pathogens/ antigens introduced in mouth/by injection
2)exposure to antigens activates b cell to go through clonal expansion
3) b cells undergo mitosis and these cells differentiate into plasma/ memory b cells
4) plasma makes ab
5) b memory divide into plasma when reinfected w same pathogen
herd immunity
when enough of the population is vaccinated so pathogen cannot spread easily amongst pop- protection for unvaccinated
direct monoclonal therapy
uses monoclonal abs designed w a complimentary binding site to antigens on outside of cancer cell
abs attach to cancer cells and prevent chemicals from binding to cancer cells
so prevent cancer cells from growing
DONT cause harm to normal cells as only attach to cancer cells
indirect monoclonal therapy
uses monoclonal abs complementary to antigens outside cancer cells which have drugs attached to them
camcer drugs delivered directly to cancer cells and kill them
reduces harmful sideeffects chemotherapy and radiotherapy produce
‘bullet drugs’
ELISA test
1) add test sample from patient to base of beaker
2) wash to remove unbound sample
3) add ab complementary to antigen testing for
4) wash to remove any unbound ab
5) add 2nd ab complementary to 1st ab and binds to it. 2nd ab has enzyme attached
6) substrate for enzyme (colourless) is added. this produces coloured products in presence of enzyme
7) presence of colour= presence of atigen
intensity of colour= quantity present
HIV replication
1) HIV transported around blood til attaches to CD4 protein on helper T cell
2) HIV protein capsule fuses w helper t cell membrane- enables RNA and enzymes from HIV to enter
3) reverse transcriptase copies viral RNA into a DNA copy and moves to helper t cell nucleus
4) mRNA transcribed and helper t cells start to create viral proteins to make new viral particles
