Practicals Flashcards
method to investigate substrate concentration effecting initial rate of reaction
( same for enzyme concentration)
- use a range of at least 5 substrate concentrations
- use an enzyme conc/volume that won’t limit rate
- measure volume of gas produced/ colour change/ product
- use tangent
Describe how to use a light microscope
start with lowest magnification objective lens
put slide on stage - secure with stage clips
use focus to move stage close to the lens
adjust focus and light intensity to get clearest image
Describe the eyepiece graticule
see through ruler in the eyepiece
no units
describe the stage micrometer
a slide with 1 um markings
describe how to use the stage micrometer
set magnification
record how many eyepiece graticule units is equal to one micrometer
dont change magnification
view specimen and use scale to calculate actual size
What is the root tip squash used for?
calculate mitotic index/ see mitosis
Method - Root tip squash
use a fixative to prevent enzyme action remove 1 mm of the root tip add stain (nile blue) add cover slip without trapping air squash vertically
slide preparation
add distilled water to a microscope slide
the sample has to be thin
water molecules holds in place by adhesion
stain
add cover slip
why do we use stains
identify types of cells/ different cells
stains make the sample absorb more light - visible
What is the Mitotic index and how is it calculated?
used to investigate the % of cells undergoing mitosis
(no of cells in mitosis/ total no of cells) x 100
where is the mitotic index high?
at growing regions (meristem)
what are common issues with calculating mitotic index?
use a fixative, use a stain, multiple layers of stains
how could you use mitotic index to investigate the use of herbicide?
use a range of 5 herbicide concs, control all variables, plot mitotic index of graph, use lowest conc when mitotic index is 0
Describe identifying the water potential of plant tissue
prepare serial dilution from a stock solution cylinders of plant tissue with the same SA weigh mass @ start submerge for 1 hour blot dry with a paper towel weigh again and calculate the % change plot calibration curve and estimate isotonic when % change = 0
equation to calculate volume of stock required with serial dilution
(total amount/ stock concentration)x desired conc
what is a colourimeter?
instrument that quantitatively measures the colour intensity of a solution (measures absorbance/ transmission)
cuvette
rectangular test tube for colourimetry
Colourimeter method
use a blank for comparison
make a calibration curve by plotting samples
read off unknown value to find concentration
what is serial dilution used for?
calibration curves, viable cell count
10 fold serial dilution
add 1cm of original to 9 cm of distilled water (repeat)
what does a potometer measure?
rate of transpiration
control (potometer)
light intensity/ wavelength
temperature
air movement/ humidity
equation for transpiration rate
(distance bubble moves x cross sectional area) / time taken
common errors with potometer
water used for turgidity used for photosynthesis respiration makes water not all stomata covered/ leaves removed air bubbles in xylem error in reading
