Core Pracs Flashcards
How to approach ‘Devise an experiment’ Q?
IDCORSS
Dependent variable (equipment, measurements, how to calculate it)
Independent variable (list range of concs/temp tested, at least 5, equipment)
Controls/control variables (eg water as it’s 0 moldm-3, state what you’re controlling, how and why)
Organism (mass, age, species, length)
Repeats (at least 3 times, calculate a mean) (identify and remove anomalies)
Stats test (chi squared/graph-state what you’re plotting/standard deviation as bars on graphs, overlap=no significance)(simpson’s index)(t-test)
Safety (risk assessment, precautions, ethical considerations)
How to investigate trypsin conc affecting the initial rate of reaction? (CP1)
Dilute trypsin with distilled water making 0.2%, 0.4%, 0.6%, 0.8%
distilled water is control
add 2cm3 milk suspension to each conc and test for colorimeter absorbance at 15 second intervals
As conc of trypsin increases….
rate of reaction increases as number of enzyme-substrate complexes forming increases
why does rate plateau after a few minutes in enzyme substrate reaction?
Because all substrates have occupied an active site
what are the 4 factors that affect enzyme activity?
- temp
- pH
- enzyme conc
- substrate conc
how to set up control when measuring enzyme activity?
use distilled water or boiled enzyme solution instead of enzyme solution
how can colorimeter determine RoR of trypsin and milk?
as trypsin digests proteins in milk, milk becomes more translucent
value in colorimeter decreases as digestion increases
how to calculate RoR from time?
1/time
what is microscopy used for?
to increase magnification and resolution of object
what is the formula for magification?
I / A x M
how to use light microscope to observe and measure biological samples?
- calibrate eyepiece graticule and line it up with stage micrometer
- cut THIN transverse section of plant stem
- place on slide, add stain and cover slip. ensure no air bubbles
- set objective lens to lowest magnification
- draw it out
what are rules for label lines in biological drawings?
must use ruler and draw horizontal line
what are the magnifications of eyepiece and objective lenses?
10x eyepiece
objective comes in low, medium, high
what is the mitotic index of a sample?
ratio of cells undergoing mitosis to the total number of cells in a sample
what are some common risk assessment factors?
- scalpel/scissor - risk cuts
- acids/dyes - risk irritatoin
- glass equipment - risk cuts
how to find mitotic index of a garlic clove? (Core prac procedure)
- heat HCl in waterbath
- cut small sample of root tip using scalpel
- add stain (acetic orcein)
- Macerate with needle, make 1 thin layer
- cover slip, ensure no air bubbles#
- gently press tgt
where in plants can cells undergoing mitosis be found?
meristem tissues at root and shoot tips
what is the formula of mitotic index?
of cells w visible chromosomes / total ~ of cells in sample
why is garlic root tip placed in hot HCl?
to dissolve middle lamellae, breaking up cellulose cell wall
so dye can stain