Pracs stuff Flashcards
How would a researcher prepare the epidermis of leaves from crops to be viewed under a microscope 5
Gather a fresh sample of leaves from several crops
Tear the leaves and use forceps and gloves to cleanly peel away the epidermis
Place the epidermis on a clean slide on a drop of water
place a cover slide over this using a mounted needle and wipe away excess
stain if necessary
What microscopes can see viruses?
An electron microscope
When preparing a slide for a light microscope, what actions could be taken to prevent contamination of the slide? 2
Wear gloves when handling the epidermis and slide
Use forceps to transfer the epidermis
How does wearing gloves prevent contaminating the slide? 2
Prevents bacteria or other microbes/debris on the hand from infecting the specimen
which may show up under the microscope
How does using forceps prevent contamination of the slide?2
This prevents germs from contaminating the slide
and prevents physical distortion by the poor grip of the hand
The researcher observes slides with an objective lens, magnification x4. The overall magnification is x40. what is the magnification of the eyepiece lens?
4 x ?=40, 40/4= 10
therefore x10
Under x40 magnification, the bacterium found in the epidermis is 0.5 mm in the drawing. What’s the actual size of the bacterium in micrometres?
M=x40 I=0.5
A=I/M = 0.5/40=0.0125 x1000
=12.5 um
With a x10 eyepiece lens and a x4 objective lens, the stage graticule covers 20 EPU on the eyepiece graticule. How much does 1 EPU represent?
Stage graticule= 1000 um always
1000 covers 20 EPU
1EPU= 1000/20=50um
Across several slides, the bacteria appear to take on different shapes. They are all of the same strain, what explanation would clarify the different shapes observed? 2
The bacteria have similar 3D shapes, yet the 2D slices of tissue cuts them at various planes
in a 2D slide, they will appear to be different shapes.
See screenshot in as bio ass, State both the independent and the dependent variable in the experiment
Independent: pH
dependent: time taken for no colour change
ss What colour change will be observed at the start of the test, when the starch is more plentiful?
(colour change means you must say what it starts as and what it ends as)
From yellow to blue/black
ss State 2 variables that need to be controlled for this experiment, and explain how you would control them 6
temperature:
use thermostatically controlled water bath
concentration of starch/substrate:
use starch solution from the same prepared stock solution
Concentration of enzyme: use enzyme solution from the same prepared stock solution
ss The student’s lab partner notes that his partner sometimes pipetted the mixture onto the tile quickly, other times slowly. Why could this effect the accuracy of the results? 3
The reaction style proceeds within the pipette, which contains both enzymes and substrate
If too slow, more starch will have been hydrolysed in the delay
and the colour change will not correspond to what it should have been. It will be less of a change
Why did amylase at pH 13 take too long to hydrolyse the starch? 4
The enzyme worked best at mid-range pH
lack of function at high pH of 13 indicates this is far from the optimum. The amylase is likely denatured
The high pH alters hydrogen bonding, and the enzyme active site loses it’s specific tertiary structure
So starch is no longer complementary to it’s shape so hydrolysis will be impaired
