Required Practicals Flashcards
rp1
effect of a variable on enzyme controlled reaction
temperature, pH, conc of enzyme/substrate
IV- temperature
DV- time taken for enzyme to break down substrate
method
set up water baths at different temps
put starch test tube in water bath and equilibrate
put amylase test tube in water bath and equilibrate
after 5 mins add amylase to starch
dip glass rod in starch amylase every minute and dip into iodine
repeat until iodine stops turning from blue to black
conclusion
glucose turns iodine from blue to black
as temp increase, kinetic energy increases so more ESC will form and will break down starch to glucose
after it passes optimum, enzyme denatures, breaks bonds, changes tertiary structure so active site is no longer complementary and starch can’t bind- no ESC
no glucose so iodine won’t turn blue black
rp2
stained squashes of cells from plant root tips
set-up and use of an optical microscope to identify the stages of mitosis in these stained squashes
calculation of a mitotic index
method rp2
cut sample of root tip
add acid to halt mitosis
place on slide and add stain so you can see chromosomes
squash so that cells are separated- single layer of cells (light can pass through)
no air bubbles
place under optical microscope and correctly adjust
mitotic index rp2
number of cells undergoing mitosis/total number of cells
total number of cells at each stage is proportional to time each cell spends undergoing each stage
time in stage- number of cells in stage x cycle time/ total number of cells
rp3
production of a dilution series of a solute to produce a calibration curve with which to identify the water potential of plant tissue (apple)
IV- concentration of solute
DV-% change in mass
method
make serial dilution of 1M sucrose (0-1 conc) in six boiling tubes
Volume of stock needed = (desired conc ÷ conc of stock solution) x desired volume
add to water baths at 30C
use cork borer to cut out cylinders of apple + blot to remove excess water
record starting mass and place in boiling tubes for 30mins
remove, blot and weigh final mass
calc % change and plot graph
conclusion
where graph crosses 0 the solution was isotonic- not net water movement
lower sucrose concentration- increased in mass as water moved in from high to low by osmosis (hypotonic, turgid)
higher sucrose concentration- decreased in mass as water moved out from high wp to low wp by osmosis
(hypertonic, flaccid)
%change- final mass-starting mass/starting mass x100
rp6
use of aseptic techniques to investigate the effect of antimicrobial substances on microbial growth
IV- type of antibiotic
DV- zone of inhibition around disc
aseptic techniques
used to prevent contamination of bacterial cultures and surrounding environment
wipe down surfaces with antibacterial
use bunsen burner - convection currents draw microbes up
flame wire hoop
flame neck of bottles
method
carry out aseptic techniques
use sterile pipette to transfer bacteria to agar plate
spread bacteria over agar plate
use sterile forceps to place antibiotic discs onto agar
tape a lid on and invert ( prevents condensation dropping)
incubate then measure zone of inhibition without removing lid
make sure there is o2 so they can respire and don’t produce anaerobic bacteria which is harmful.
conclusion
larger zone of inhibition shows the bacteria has killed more bacteria, more effective
smaller zone shows bacteria may be resistant to that antibiotic
rp9
investigation into the effect of a named variable on the rate of respiration of cultures (yeast) of single-celled organisms
IV- temperature
DV- time taken for methylene blue to go colourless
method rp9
set up water bath at 35C
add yeast and glucose to 3 test tubes and put in water bath
add methylene blue (redox indicator) to test tubes, shake and put in water bath
shake to allow oxygen
repeat with higher temps and calc mean time
