Required Practical Questions Flashcards
A student carried out an investigation into the mass of product formed in an enzyme - controlled reaction at three different temperatures.
Only the temperature was different for each experiment.
The results are shown in the graph ( Graph is like a rate of reactions graph )
Use your knowledge of enzymes to explain
Why the initial rate of reaction was higher than 55 degrees celsius.
- Substances have more kinetic energy
- increased amount of collisions
A group of students carried out an investigation to find the water potential of potato tissue.
The students were each given a potato and 50 cm^3 of a 1.0 mol dm^-3 solution of sucrose.
- They used the 1.0 mol dm^-3 solution of sucrose to make a series of different concentrations.
- They cut and weighed discs of potato tissue and left them in the sucrose solutions for a set of time.
- They then removed the discs of potato tissue and reweighed them.
The table below shows how one student presented his processed results
Concentration of sucrose solution / mol dm^-3 1 ) 0.15 2 ) 0.20 3 ) 0.25 4 ) 0.30 5 ) 0.35 6 ) 0.40 Percentage change in mass of potato tissue 1 ) +4.7 2 ) +4.1 3 ) +3.0 4 ) +1.9 5 ) -0.9 6 ) -3.8
Explain why the data in the table above are described as processed results.
- Calculations made from the raw data would have recorded initial and final mass
Describe how you would use a 1.0 mol dm^-3 solution of sucrose to produce 30 cm^3 of a 0.15 mol dm^-3 solution of sucrose.
- Add 4.5 cm^3 of sucrose solution to 25.5 cm/63 of distilled water
( 0.15 / 1.0 ) x 30 = 4.5 cm^3 of sucrose )
( 30 - 4.5 = 25.5 cm^3 of water )
Explain the change in mass of potato tissue in the 0.40 mol dm^-3 solution of sucrose.
- Water potential of solution is less then the potato tissue
- Tissue loses water by osmosis
Describe how you would use the student’s results in the table above to find the water potential of the potato tissue.
- Plot a graph with concentration on the x - axis and percentage change in mass on the y - axis
- Find the concentration where the curve crosses the x - axis
- Use another resource to find the water potential of sucrose concentration
A student investigated mitosis in the tissue from an onion root tip.
The student prepared a temporary mount of the onion tissue on a glass slide.
She covered the tissue with a cover slip.
She was then given the following instructions.
” Push down hard on the cover slip, but do not push the cover slip sideways. “
Explain why she was given this instruction.
- To spread the tissue
- But avoid rolling cells together
The image below shows one cell the student saw in the onion tissue.
( Image shows a cell in anaphase )
The student concluded that the cell in the image above was in the anaphase stage of mitosis.
Was she correct?
Give two reasons for your answer.
- Correct as the chromosomes are at the poles of the spindle
- U - shape shows that chromatids are being pulled apart from their centromere
The student counted the number of cells she observed in each stage of mitosis.
Of the 200 cells she counted, only six were in anaphase.
One cell cycle of onion root tissue takes 16 hours.
Calculate how many minutes these cells spend in anaphase.
Show your working.
- 6 / 200 are in anaphase
- ( 6 / 200 ) x ( 16 x 60 ) = 28.8 ( converted 16 hours into minutes )
A student prepared a stained squash of cells from the tip of an onion root and observed it using an optical microscope.
During the preparation of the slide, he:
- Cut the first 5 mm from the tip of an onion root and placed it on a glass slide
- Covered this tip with a drop of stain solution and a cover slip
- Warmed the glass slide
- Pressed down firmly on the cover slip
He identified and counted nuclei in different stages of the cell cycle.
Explain why the student:
- Used only the first 5 mm from the tip of an onion root
- Most mitosis occurs at the root tip
- Pressed down firmly on the cover slip.
- Spread out cells so light passes through
Figure 1 shows the cells the student saw in one field of view.
He used this field of view to calculate the length of time these onion cells spent in anaphase of mitosis.
( Image shows a number of cells in different stages of mitosis )
Scientist have found the mean length of time spent by onion cells in anaphase of mitosis is 105 minutes.
They also found the cell cycle of cells in the onion root shown in figure 1 takes 1080 minutes.
32 whole cells are shown in figure 1
Use this information and figure 1 to calculate the length of time the cells of this onion root are in anaphase and then calculate the percentage difference between your answer and the mean length of time found by the scientist.
Show your working.
- 35.7 %
Tick the name given to the division of cytoplasm during the cell cycle.
- Cytokinesis
Describe and explain what the student should have done when counting cells to make sure that the mitotic index he obtained for this root tip was accurate.
- Repeat count
- To ensure figures are correct
A scientist treated growing tips of onion roots with a chemical that stops roots growing.
After 24 hours, he prepared a stained squash of these root tips.
Figure 2 is a drawing showing the chromosomes in a single cell observed in the squash of one of these root tips in anaphase.
This cell was typical of other cells in anaphase in these root tips.
( Image shows an uneven amount of chromatids on each pole of the cell )
Use all of this information to suggest how the chemical stops the growth of roots.
- Stops anaphase
- by disrupting spindle fibre formation
- Preventing separation of chromatids
Give three properties of water that are important in biology.
- Cohesion
- is a solvent
- is a metabolite
