Required Practical 1-6 & How Science Works Flashcards

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1
Q

RP1 (Enzymes)

A

Concentration of substrate solution

Concentration of enzyme solution

pH

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2
Q

RP1 (Enzymes)

Calculate the rate of reaction at 25°C.

A

DY (change in Y) / DX (change in X = time)

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3
Q

RP1 (Enzymes)

Describe the differences between the two curves (2 marks)

A
  1. Initial rate of reaction faster at 37 °C;
  2. Graph reaches plateau at 37 °C;
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4
Q

RP1 (Enzymes)

Explain the differences between the two curves (3 marks).

A

(Initial rate of reaction faster at 37 °C);

  1. Because more kinetic energy;
  2. So more enzyme substrate complexes formed;

(Graph reaches plateau at 37 °C);

  1. Because all substrate used up.
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5
Q

RP1 (Enzymes)

When investigating factors that affect enzyme-controlled reactions, enzymes are often ‘isolated’ from a cell (e.g. a bacterial cell).

Explain why this is a limitation?
.

A

The process of isolation may change the enzyme’s activity

Outside the optimum conditions of the host cell, the enzyme’s activity may also change.

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6
Q

RP1 (Enzymes)

What is a common control condition that proves a specific enzyme is needed for a reaction?

A
  1. Boiled enzyme
  2. At same concentration & volume
  3. This denatures the enzyme and the reaction will not take place in this condition
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7
Q

RP1 (Enzymes)

A

Mark in pairs, 1 and 2 OR 3 and 4 OR 5 and 6

  1. Boil OR Add (strong) acid/alkali;
  2. Denatures the enzyme/ATP synthase;
  3. Put in ice/fridge/freezer;
  4. Lower kinetic energy so no enzyme-substrate complexes form;
  5. Add high concentration of inhibitor;
  6. Enzyme-substrate complexes do not form;
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8
Q

RP1 (Enzymes)

A
  1. Same volume of (each) buffer/pH solution;
  2. Same concentration/mass of substrate (at start);
  3. Same concentration/mass of denatured enzyme;
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9
Q

RP2 (Mitosis)

What is the equation for the mitotic index?

A
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10
Q

RP2 (Mitosis)

Describe how you would determine a reliable mitotic index (MI) from tissue observed with an optical microscope.

Do not include details of how you would prepare the tissue observed with an optical microscope (3 marks).

A
  1. Count cells in mitosis in field of view;
  2. Divide this by total number of cells in field of view;
  3. Repeat many/at least 5 times
    (to calculate a reliable mean mitotic index)

OR Select (fields of view) at random;

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11
Q

RP2 (Mitosis)

A student prepared a plant root to observe cells undergoing mitosis.

He put the root in a small bottle of hydrochloric acid in a 40 °C water bath.

Why did he put the plant root in acid?

A

To stop mitosis

To break down links between cells/cell walls

To separate cells/cell walls

To break down/hydrolyse cellulose/cell wall

Allowing the stain to pass/diffuse into the cells

Allowing the cells to be (more easily) squashed

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12
Q

RP2 (Mitosis)

State two precautions required when working with hydrochloric acid.

A
  1. Eye protection;
  2. Gloves;
  3. Add water to spills (immediately);
  4. Do not pour away down sink
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13
Q

RP2 (Mitosis)

Pressing the coverslip downwards enabled the student to observe the stages of mitosis clearly.

Explain why (2 marks).

A
  1. To create a single/thin layer of cells

OR to spread out cells;

  1. So that light could pass through;
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14
Q

RP2 (Mitosis)

A

Where dividing cells are found / mitosis occurs;

OR

No dividing cells / mitosis in tissue further away / more than 5 mm from tip;

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15
Q

RP2 (Mitosis)

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 (2 marks).

A

Description and explanation required, so mark as pairs only

  1. Examine large number of fields of view / many cells;
  2. To ensure representative / reliable sample;

OR

  1. Method to deal with part cells shown at edge /count only whole cells;
  2. To standardise counting;
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16
Q

RP2 (Mitosis)

A
  1. Stops anaphase / cell division / mitosis;

Accept prevents telophase / cytokinesis

  1. (By) stopping / disrupting / spindle fibres forming / attaching / pulling;
  2. Preventing separation of (sister) chromatids;

Accept chromatids split

  1. (So) no new cells added (to root tip);
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17
Q

RP2 (Mitosis)

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.

A

28.8 minutes

Working out:
6 / 200 = proportion in anaphase

Multiply this answer by 16 x 60 (convent into minutes).

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18
Q

RP2 (Mitosis)

When comparing the mitotic index in the roots of two different species.

Give two considerations to ensure this comparison is valid.

A

1. Roots/plant of the same age;

2. Same growing conditions (for all roots);

3. Same distance from root tip;

4. Same time in acid
OR Same temperature of acid;

5.Same concentration of acid;

6. Several fields of view (for each species) to calculate a mean / reliable mitotic index;

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19
Q

RP2 (Mitosis)

The dark stain used on the chromosomes binds more to some areas of the chromosomes than others, giving the chromosomes a striped appearance.

Suggest one way the structure of the chromosome could differ along its length to result in the stain binding more in some areas.

A

Differences in base sequences

OR

Differences in histones/interaction with histones

OR

Differences in condensation/(super)coiling;

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20
Q

RP3 (Osmosis)

Describe how you would use a 1.0 mol dm−3 solution of sucrose to produce 30cm3 of a 0.15 mol dm−3 solution of sucrose.

Clue: C1 x V1 = C2 x V2

A

Answer = Add 4.5 cm3 of (1.0 mol dm–3) solution to 25.5 cm3 (distilled) water.

Step-by-step working:
C1 x V1 = C2 x V2
1 x V1 = 0.15 x 30
V1 = (0.15 x 30) / 1
V1 = 4.5cm3

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21
Q

RP3 (Osmosis)

A

Calculations made (from raw data)

OR raw data would have recorded initial and final masses.

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22
Q

RP3 (Osmosis)

A
  1. Water potential of solution is less than / more negative than that of potato tissue;

Allow Ψ as equivalent to water potential

  1. Tissue loses water by osmosis (so masses decreases).
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23
Q

RP3 (Osmosis)

A

1. Plot a graph with concentration on the x-axis and percentage change in mass on the y-axis;

2. Find concentration where curve crosses the x-axis / where percentage change is zero;

3. Use (another) resource to find water potential of sucrose concentration (where curve crosses x-axis).

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24
Q

RP4 (Membrane damage)

What is uncertainty?

A

The amount of error your measurements might contain

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25
Q

RP4 (Membrane damage)

How do you calculate uncertainty?

A

Is always HALF of the smallest interval you can read with the measuring equipment you are using.

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26
Q

RP4 (Membrane damage)

What is the uncertainty of a measuring cylinder where the smallest interval is 20mls?

A

10mls

Uncertainty is always HALF of the smallest interval

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27
Q

RP4 (Membrane damage)

What is the uncertainty of a ruler and why?

A

1mm

This is because you measure twice at both ends with a ruler. So you add the uncertainties together:

0.5mm + 0.5mm = 1.0mm

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28
Q

RP4 (Membrane damage)

What is the equation for percentage error?

A
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29
Q

RP4 (Membrane damage)

Calculate the percentage error when measuring 50mls using a cylinder with the smallest interval of 5mls.

A

(2.5 / 50) x 100 = 5%

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30
Q

RP4 (Membrane damage)

What is the uncertainty of this measuring cylinder in mls?

A

1 ml

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31
Q

RP4 (Membrane damage)

What is the percentage error if measuring 15mls using this measuring cylinder? (to 1dp).

A

(1 / 15) x 100 = 6.7%

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32
Q

RP4 (Membrane damage)

Suggest how you could reduce the uncertainty calculated using this measuring cylinder

A

Use instrument with smaller intervals

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33
Q

RP4 (Membrane damage)

Give one way in which a student could ensure their beetroot cylinders were kept at 25 °C throughout the experiment.

A

Measure temperature (in tube) at intervals and use appropriate corrective measure (if temperature has fluctuated);

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34
Q

RP4 (Membrane damage)

In an experiment investigating the impact of increasing temperature on the permeability of beetoot.

List the key control variables.

A
  1. (Of beetroot cylinders):

Length and diameter

OR Surface area

OR Volume

OR Mass/weight (of cylinders);

  1. Time in water/solution;
  2. The volume of water/solution used
    (so they complete submerge the cylinder)
35
Q

RP4 (Membrane damage)

A
  1. Water/25oC caused no damage/no pigment release (in E);
  2. (Damage to) cell(-surface) membrane / phospholipid bilayer;
  3. Ethanol/acid caused some/similar/identical damage

OR 70oC caused most damage;

Accept description of ‘pigment release’ for ‘damage’

  1. (By) ethanol dissolving phospholipid bilayer
  2. (By) 70oC denaturing/altering membrane protein

OR (By) 70oC increasing fluidity/permeability of membrane;

36
Q

RP4 (Membrane damage)

The cells of beetroot contain a red pigment. A student investigated the effect of temperature on the loss of red pigment from beetroot. He put discs cut from beetroot into tubes containing water. He maintained each tube at a different temperature.

After 25 minutes, he measured the percentage of light passing through the water in each tube.

(a) The student put the same volume of water in each tube.

Explain why it was important that he controlled this experimental variable.

A
  1. (If) too much water the concentration of pigment (in solution) will be lower / solution will appear lighter / more light passes through (than expected);

OR

(If) too little water the concentration of pigment (in solution) will be greater / solution will appear darker / less light passes through (than expected);

  1. So results (from different temperatures) are comparable;
37
Q

RP4 (Membrane damage)

The decrease in the percentage of light passing through the water between 25 °C and 60 °C is caused by the release of the red pigment from cells of the beetroot.

Suggest how the increase in temperature of the water caused the release of the red pigment (2 marks).

A
  1. Damage to (cell surface) membrane;
  2. (membrane) proteins denature;
  3. Increased fluidity / damage to the phospholipid bilayer;
38
Q

How science works (AO3)

Suggest appropriate units the student should use to compare the distribution of stomata on leaves.

A

Stomata per mm^2 or cm^2

39
Q

How science works (AO3)

Give two reasons why it was important that the student counted the number of stomata in several parts of each piece of leaf tissue.

A

1. Distribution may not be uniform

OR So it is a representative sample;

2. To obtain a (reliable) mean;

40
Q

RP5 (Dissection)

Give three control measures to reduce the risks associated with carrying and using a scalpel.

A

1. Carry with blade protected

OR carry pointing down

OR Do not carry if likely to be jostled;

2. Cut away from body;

3. Cut onto hard surface / tile / board;

4. Use sharp blade;

5. Disinfect/dispose of used scalpel (blade) as instructed;

41
Q

RP5 (Dissection)

A

1. Only use single lines/do not use sketching (lines)/ensure lines are continuous/connected;

2. Add labels/annotations/title;

3. Add magnification/scale (bar);

4. Draw all parts to same scale/relative size;

5. Do not use shading/hatching;

42
Q

RP5 (Dissection)

Describe two precautions the student should take when clearing away after a heart dissection.

A

1. Carry/wash scalpel / sharp instruments by holding handle

OR Carry/wash scalpel / sharp instruments by pointing away (from body)/down;

2. Disinfect instruments/surfaces;

3. Disinfect hands

OR Wash hands with soap (and water);

4. Put organ/gloves/paper towels in a (separate) bag/bin/tray to dispose;

43
Q

RP5 (Dissection)

Give two safety precautions that should be followed when dissecting a heart.

A

1. Use a sharp scalpel/scissors

2. Wash hands with soap / wear gloves

3. Disinfect bench/equipment

4. Cover any cuts

5. Cut away from self AND on a hard surface

6. Safe disposal (of scalpel / biological waste)

44
Q

RP5 (Dissection)

Scientists dissected gills from several species of fish. They recorded:

*   the mass of the whole fish
*   the total number of gill filaments
*   the mean length of one filament
*   the mean number of lamellae per mm
*   the mean surface area of one lamella.

It was not possible for the scientists to measure the length of every filament and the surface area of every lamella.

Suggest how they collected data to give a reliable mean for these variables (2).

A
  1. Random samples;
  2. Large sample size;
45
Q

How science works (AO3)

The scientists estimated the mean mass of fibre eaten per day using a food frequency questionnaire (FFQ).

The FFQ asks each person how often they have eaten many types of food over the past year.

An alternative method to calculate fibre eaten is for a nurse to ask each person detailed questions about what they have eaten in the last 24 hours.

Suggest one advantage of using the FFQ method and one disadvantage of using the FFQ method compared with the alternative method.

A

Advantage
Over longer period so more representative;

OR Diet may vary during the year/from day to day;

OR More cost effective because fewer people/nurses required;

Disadvantage
Relies on (long term) memory so may not be accurate

OR Recall of 24 hr diet likely to be more accurate

46
Q

How science works (AO3)

Blood cells can be counted using a haemocytometer (see below). When counting, cells that touch top or left lines are counted but cells that touch right or bottom lines are not counted.

Suggest two reasons for this rule.

A

1. To avoid dealing with parts of cells;

2. To avoid counting same cells twice / more than once;

3. To be consistent / get comparable results;

OR more accuracy

47
Q

How science works (AO3)

A doctor used a haemocytometer (see below) to count white blood cells per mm3.

When counting white blood cells, the doctor only diluted the blood sample by a factor of 20 times, instead of 200 times when counting red blood cells.

Suggest why he only diluted the sample by a factor of 20 times.

A

There are fewer white cells, so no need to dilute (further to see enough);

OR accept converse i.e. too few to see if greater dilution / at 200 times;

48
Q

How science works (AO3)

Explain how a stain allowed doctor to count the white blood cells amongst all the red blood cells in a blood sample.

A

White blood cells have a nucleus (that stains but red cells do not);

49
Q

How science works (AO3)

A

Median

Reason
Presence of outliers / anomalies e.g. 80, 70

OR small sample size/8 (measurements);

50
Q

How science works (AO3)

Suggest why the scientist made repeat measurements.

A

Increases reliability (of results)

OR

Anomalous results can be identified;

51
Q

How science works (AO3)

The scientist used the reduction in total leaf area of the experimental plants as an indicator of plant growth.

Outline a method by which you could find the area of a plant leaf.

A

Draw around leaf on graph paper and count squares;

52
Q

How science works (AO3)

The scientists’ hypothesis at the start of the investigation was that crop plants genetically engineered to produce the protein GB would become more resistant to high environmental temperatures.

The scientists developed this hypothesis on the basis of previous research on crops that are grown in hot climates.

Suggest how the scientists arrived at their hypothesis.

A

1. Looked for information / journals / research, on crop plants that grow at high temperatures;

2. Crop plants cited in this research contain / make GB;

3. So assumed making plants produce GB makes them resistant to high temperatures;

53
Q

RP6 (Aseptic Techniques)

What is an antimicrobial?

A

A molecule / drug / chemical that inhibits the growth OR causes the cell death of a microorganism

Micoorganisms are often referred to as ‘microbes’

54
Q

RP6 (Aseptic Techniques)

Antimicrobial examples

A

Antibiotics
Antivirals
Antifungals
Antiparasitics

55
Q

RP6 (Aseptic Techniques)

Main goal of using aseptic techniques

A

Prevent contamination from unwanted microorganisms / microbes

56
Q

RP6 (Aseptic Techniques)

A student added 100 mm^3 of a bacterial culture from its glass bottle onto a separate agar plate.

They spread each bacterial culture evenly over the agar using a spreader.

Describe the aseptic techniques they should use (3).

A

Any 3 from:
1. Wash hands with soap OR Disinfect surfaces;
2. Use sterile pipette/syringe (to transfer bacteria);
3. Remove bottle lid and flame neck of bottle;
4. Lift lid of (agar) plate at an angle;
5. Work close to upward air movement / convection current;
6. Use sterile spreader / flame spreader;
7. Place pipette/spreader into disinfectant immediately after use;

57
Q

RP6 (Aseptic Techniques)

Explain the purpose of washing hands with soap

A

To remove/kill microbes

58
Q

RP6 (Aseptic Techniques)

Explain the purpose of working close to a bunsen burner

A

to create an upward current of air
(that moves away contaminating microbes)

59
Q

RP6 (Aseptic Techniques)

Explain the purpose of disinfecting the work bench

A

To kill microbes and prevent contamination

60
Q

RP6 (Aseptic Techniques)

Explain the purpose of flaming the equipment (e.g. spreader / innoculation loop) when transferring bacteria from culture bottles to an agar plate.

A

sterilise / kill microbes / prevent contamination

61
Q

RP6 (Aseptic Techniques)

Explain the purpose of lifting the lid of the petri dish at angle

A

prevent entry of microbes

62
Q

RP6 (Aseptic Techniques)

What is a colony?

A

1 bacteria that has multiplied many times via binary fission to form a visible colony

63
Q

RP6 (Aseptic Techniques)

Purpose of ‘broth’ AND ‘agar’ in bacterial cultures

A

Provides named nutrients for microbe growth e.g., galactose, glucose, amino acids, mineral ions

64
Q

RP6 (Aseptic Techniques)

A student used a dilution series to investigate the number of cells present in a liquid culture of bacteria.

Describe how he made a 1 in 10 dilution and then used this to make a 1 in 1000 dilution of the original liquid culture of bacteria.

A

1. Add 1 part bacteria culture to 9 parts sterile liquid (e.g. broth/water) to make 1 in 10 dilution;
2. Mix well;
3. Add 1 part of 1 in 10 and 9 parts fresh sterile liquid to make 1 in 100 dilution;
4. Mix well;
5. Add 1 part of 1 in 100 and 9 parts fresh sterile liquid to make 1 in 1000 dilution;

65
Q

RP6 (Aseptic Techniques)

A student transferred 0.5 cm^3 of a 1 in 10,000 dilution to an agar plate and after a 24-hour incubation counted 57 colonies.

How many bacteria are present in the original culture of 1cm^3?

A

57 x 10000 = 570,000 in 0.5cm^3

570,000 x 2 in 1cm^3

= 1.14 x 10^6

Always multiply the dilution factor!

66
Q

RP6 (Aseptic Techniques)

A

Always multiply by the dilution factor!

67
Q

RP6 (Aseptic Techniques)

Why did the student transfer the same volume of bacteria culture onto each agar plate.

A

So same number of bacteria transferred to allow comparison

68
Q

RP6 (Aseptic Techniques)

Explain why agar was boiled before adding to the petri dish

A

So no contamination / other bacteria present

69
Q

RP6 (Aseptic Techniques)

Equation for estimating population of cells that double each division e.g. bacteria, cancer cells.

A
70
Q

RP6 (Aseptic Techniques)

Starting with one bacteria cell, how many bacteria would be present after 17 divisions.

Give your answer in standard form.

A
71
Q

RP6 (Aseptic Techniques)

Starting with 17 bacteria cells, how many bacteria would be present after 30 divisions.

Give your answer in standard form.

A
72
Q

RP6 (Aseptic Techniques)

Equation for determining how many divisions produced a total number of cells e.g. bacteria.

A
73
Q

RP6 (Aseptic Techniques)

A
74
Q

RP6 (Aseptic Techniques)

A
75
Q

RP6 (Aseptic Techniques)

Why use a logarithmic scale on a graph?

A

Allows numbers with a large range or differences to be presented

76
Q

RP6 (Aseptic Techniques)

What are logs?

A
77
Q

RP6 (Aseptic Techniques)

A
78
Q

RP6 (Aseptic Techniques)

A student investigated cinnamon oil as an antimicrobial.

Suggest exactly what the student added to the petri dish as a positive control AND negative control.

A

(Positive control = will decrease microbe numbers)

1. Antimicrobial / antibacterial (solution)

OR Antibiotic OR Antiseptic/disinfectant;

(Negative control = no effect on microbe numbers)

2. Sterile water

OR Oil (without cinnamon);

79
Q

RP6 (Aseptic Techniques)

Explain the below clear zones OR zones of inhibition around the antibiotic disks after 24 hours.

A

Antibiotic diffuses from disk into agar;

Bacteria resistant to antibiotic A so no clear zone;

Antibiotic B prevents growth of bacteria as shown by clear zone / zone of inhibition;

Anitibiotic C the most effective against bacterial growth as shown largest clear zone / zone of inhibition;

80
Q

How Science Works (AO3)

Why should sampling be random?

A

To reduce bias

This also make the results / experiment more reliable

81
Q

How Science Works (AO3)

Why should a sample be large?

A

To ensure it is representative;

To calculate a mean so results are more reliable;

Identify anomolus results;

82
Q

How Science Works (AO3)

The scientists’ hypothesis at the start of the investigation was that crop plants genetically engineered to produce the protein GB would become more resistant to high environmental temperatures.

The scientists developed this hypothesis on the basis of previous research on crops that are grown in hot climates.

Suggest how the scientists arrived at their hypothesis.

A

1. Looked for information / journals / research, on crop plants that grow at high temperatures;

2. Crop plants cited in this research contain / make GB;

3. So assumed making plants produce GB makes them resistant to high temperatures;

83
Q

How Science Works (AO3)

Suggest how the scientist measured the rate of water flow in a river.

A

Movement of (floating) object over known distance and over given time

OR Time to fill container of known volume

OR Use of data logging device;

84
Q

How Science Works (Maths)

A
Hint: C1 x V1 = C2 x V2