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1. Biology A-level > Practical > Flashcards

Practical Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

*

A

**INT

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2
Q

1- Food tests

A

 Reducing sugars
 Non-reducing sugars
 Proteins
 Starch
 Fats and oils

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3
Q

1- Food tests

apparatus

A

5 boiling tubes
2 test tubes
1 beaker
3 dropping pipettes
Benedict’s reagent
Dilute hydrochloric acid (0.5 mol dm-3)
Dilute sodium hydroxide/ sodium bicarbonate
Biuret reagent
Iodine- potassium iodide solution
Absolute alcohol
Glucose solution
Sucrose solution
Albumen solution
Starch solution
Oil
Water bath

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4
Q

1- Food tests

Method

Reducing Sugars

A

Reducing sugars
1. Mix 2cm3 of the test solution with an equal volume of Benedict’s reagent.
2. Heat the mixture in a water bath to between 70oC and 90oC for 5 minutes
3. Record your observations.
Food tests
Specification reference: 1.1
Chemical elements are joined together to form biological compounds
12

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5
Q

1- Food tests

Method

Non-reducing sugars

A

Non-reducing sugars
1. Mix 2cm3
of the test solution with an equal volume of Benedict’s reagent.
2. Heat the mixture in a water bath to between 70 oC and 90oC.
3. Observe and record colour change.
4. Put another 2cm3
of the test solution into a boiling tube, add 2 drops of hydrochloric
acid and heat in a water bath to 70 oC and 90 oC for 2 minutes.
5. Add 2 drops of sodium hydroxide/ small spatula of sodium bicarbonate.
6. Add 2cm3 Benedict’s reagent.
7. Heat the mixture in a water bath to between 70oC and 90oC for 5 minutes.
8. Record your observations

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6
Q

1- Food tests

Method

Proteins

A
  1. Mix 2 cm3
    of the test solution with 2 cm3
    of Biuret reagent in a boiling tube.
  2. Cover the top of the boiling tube and invert it once.
  3. Record your observations.
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7
Q

1- Food tests

Method

Starch

A
  1. Mix 2cm3
    of the test solution with 2 drops of iodine in potassium-iodide solution.
  2. Record the colour change
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8
Q

1- Food tests

Method

Fats and Oils

A
  1. Mix the fat or oil with 5 cm3
    of absolute alcohol in a boiling tube.
  2. Shake the tube.
  3. Pour the mixture into another boiling tube half full of cold water.
  4. Record your observations.
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9
Q

2 - Preparation and scientific drawing of a slide of onion cells
including calibration of actual size and magnification of drawing

A

Apparatus

Microscope fitted with an eye piece graticule
Microscope slide and cover slip
Onion
Paper towel
Scalpel
White tile
Mounted needle
Iodine solution
Forceps

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10
Q

2 - Preparation and scientific drawing of a slide of onion cells
including calibration of actual size and magnification of drawing

A

Method
1. Place two drops of water onto a microscope slide.
2. Take a small piece of onion and using forceps peel off the membrane from the
underside (the rough side).
3. Lay a piece of the membrane flat on the surface of the slide taking care that it is a
single layer and not folded back on itself.
4. Add three drops of iodine solution.
5. Place one edge of a coverslip onto the slide and lower it gently using a mounted
needle, making sure that there are no air bubbles.
6. Gently press the coverslip down using a piece of paper towel.
7. Using the x4 objective position the slide and focus on the section.
8. Swing the x10 objective into place and move the slide carefully until a clear area of
cells are observed i.e. no large bubbles, no folds and a single layer of cells.
9. Draw a group of at least three cells in the correct proportion. Indicate the length of
one cell in eye piece units on the drawing.
10. You should use the x40 objective to help you identify and label structures in the
cells.
11. Calculate the actual size of one of your cells and the magnification of your drawing.

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11
Q

3 - Investigation into the permeability of cell membranes using
beetroot

INTRO

A

INTRO
Heating the membrane can cause gaps to
form between the phospholipid molecules and the membrane will become more permeable.
The protein in the membrane can be denatured by heat

Beetroot cells contain betalain, a bright red, water soluble pigment, in the cell vacuoles. If the
cell membranes are damaged the pigment can escape from the cells and can be detected in
an aqueous medium around the tissue.

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12
Q

3 - Investigation into the permeability of cell membranes using
beetroot

APPARATUS

A

Beetroot cylinders
White tile
10 test tubes
Scalpel
250cm3 beaker
Forceps
Water baths at (25, 35,45,55,65 oC)
Thermometer
Stop clock
Colorimeter with a blue filter / colour chart

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13
Q

3 - Investigation into the permeability of cell membranes using
beetroot

METHOD

A
  1. Cut 5 same size beetroot peices eg 1cm (control SA)
  2. Wash, remove pigment from cutting
  3. Place 1 piece of beetroot into each test tube for 30 minutes, in water bath
  4. Shake the test tubes gently to make sure any pigment is well-mixed into the water, then remove the beetroot cores.
  5. Colorimeter, set it to respond to a blue/ green filter measure absorbance. Check the colorimeter reading for distilled water.
  6. Measure the absorbance/percentage transmission of each tube and plot a graph of absorbance/percentage transmission against temperature.
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14
Q

3 - Investigation into the permeability of cell membranes using
beetroot

RISK

A
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15
Q

3 - Investigation into the permeability of cell membranes using
beetroot
THINK ABOUT

A
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16
Q

3- Determination of water potential by measuring changes in mass or length
APPARATUS

A

Vegetable large enough to extract 50 mm cylinders: potatoes, sweet potatoes, yams,
beetroots, swede, turnip, parsnip and carrot are suitable.
Chopping board/ white tile
Cork borers: sizes 3 and 4 are suitable
Ruler graduated in mm
Fine scalpel
Fine forceps
5 x boiling tubes
Boiling tube rack
50cm3 measuring cylinder
Distilled water
Sodium chloride solutions (0.2, 0.4, 0.6, 0.8 moldm-3 )

17
Q

3- Determination of water potential by measuring changes in mass or length
METHOD

A
  1. Cut 15 cylinders of tissue, each approximately 50mm long, scalpel to remove any periderm (skin) as its suberin makes it waterproof and would prevent osmosis.
  2. Place 30cm3 distilled water or solution in to each test tube.
  3. Measure the length of the cylinder to the nearest mm or the mass
  4. Using the forceps, place 3 cylinders into each boiling tube.
  5. Leave at room temperature for a minimum of 45 minutes
  6. Gently blot the cylinders and re-measure the length or re-weigh the cylinders.
  7. Record your results in a table.
  8. Plot the mean percentage change against the concentration of solution.
  9. Estimate the solute potential of the tissue.
18
Q

3- Determination of water potential by measuring changes in mass or length
RISK

A
19
Q

3- Determination of water potential by measuring changes in mass or length
RESULTS

A

Percentage Change - The calculation is (end mass or length – start mass or length) ÷ start mass or length.

Where the potato tissue has lost mass or length, the answer will be a negative value.

Point at which the water potentials of the tissue and bathing solutions are equal, crosses x axis

The concentration is converted into a solute potential using a standard table. Where the solution and potato tissue have equal water potentials, the solute and water potentials are equal as the cells are in incipient plasmolysis and the pressure potential is 0 kPa.

20
Q

3- determining solute potential by the degree of incipient plasmolysis
INTRO

A
21
Q

3- determining solute potential by the degree of incipient plasmolysis
APPARATUS

A

White tile
Fine forceps
Fine scissors
Rhubarb petioles or red onion
5 x 9 cm Petri dishes, 100 cm3 beakers or watch glasses
Distilled water
sodium chloride solutions 0.2, 0.4, 0.6, 0.8 mol dm-3
: instructions for making these
solutions is given in the previous experiment.
Stopclock
Microscope slides
Cover slips
Microscope
Dropping pipettes

22
Q

3- determining solute potential by the degree of incipient plasmolysis
METHOD

A
  1. Set up five labelled Petri dishes/ small bottles each containing 10cm3 of one of the
    following solutions: distilled water, 0.2, 0.4, 0.6, 0.8 moldm-3 sodium chloride solution.
  2. Insert the fine forceps tip just under the upper epidermis of the onion leaf.
  3. Keeping the forceps handles parallel with the epidermis, so as not to penetrate the
    underlying mesophyll, grip the epidermis and, maintaining the tension in the tissue,
    pull the epidermis off the mesophyll, away from you and place into distilled water.
  4. When several square centimetres of epidermis have been peeled, place one square
    into each labelled petri dish/small bottle.
  5. Leave at room temperature for a minimum of 30 minutes.
  6. Carefully spread the tissue out on a microscope slide, so that it is not folded. Take a
    scalpel and rock the blade backwards and forwards over the tissue in order to cut out
    a 0.5 x 0.5cm square.
  7. Add two drops of bathing solution and apply a cover slip.
  8. If any solution exudes from the cover slip, blot it with filter paper to dry the slide.
  9. Using a x10 and then a x40 objective lens, examine all the cells in a field of view and
    count the number that are turgid and the number plasmolysed.
  10. Repeat the counts at all concentrations of bathing solution.
  11. Record your results in a table.
  12. Plot a graph of % cells plasmolysed against the concentration of the bathing solution.
  13. Using the graph, read the concentration of bathing solution that would produce
    plasmolysis in 50% of the cells.
  14. From the table given in the previous experiment, determine the solute potential of this
    solution. This is equal to the solute potential of the cells.
23
Q

3- determining solute potential by the degree of incipient plasmolysis
RESULTS

A
24
Q

3- determining solute potential by the degree of incipient plasmolysis
RISK

A
25
Q

4 - Investigation into the effect of temperature or pH on enzyme anxiety

A

Phenolphthalein is an indicator (pink in alkaline solutions of about pH10, colourless in pH conditions less than 8.3)

In this investigation, an alkaline solution of milk,
lipase and phenolphthalein will change from pink to colourless as the fat in milk is broken
down to form fatty acids (and glycerol) thus reducing the pH to below 8.3. The time taken for
this reaction to occur is affected by temperature.

26
Q

4 - Investigation into the effect of temperature or pH on enzyme anxiety

Apparatus

A

Apparatus
Milk, full-fat or semi-skimmed
Phenolphthalein in a dropper bottle
lipase solution (5g/ 100cm3
)
Sodium carbonate solution (0.05 moldm–3
)
5 x Test tubes and rack
2 x 10cm3 syringes/measuring cylinders
2cm3 syringe
Stirring rod
Thermometer
Water baths set to 15oC, 25 oC, 35oC, 45oC and 55oC.
Ice

27
Q

4 - Investigation into the effect of temperature or pH on enzyme anxiety
Method

A
  1. Place a beaker of lipase solution in the 25 oC water bath.
  2. Place 5 cm3
    milk, in a test tube.
  3. Add 5 drops of phenolphthalein to the test tube.
  4. Add 7 cm3 of sodium carbonate solution.
  5. Place the test tube in the 25oC water bath for 10 minutes to equilibrate.
  6. Add 1 cm3 of lipase from the beaker in the water bath and start the stop clock.
  7. Stir the contents of the test tube until the solution loses its pink colour, record the time
    taken.
  8. Repeat steps 1 – 7 for 15oC, 35oC, 45oC and 55oC.
28
Q

4 - Investigation into the effect of enzyme or substrate concentration
on enzyme activity

A
29
Q

4 - Investigation into the effect of enzyme or substrate concentration
on enzyme activity

Apparatus

A

Freshly cut potato cylinders
Pestle and mortar
Specimen tubes/test tubes
Stock solution of hydrogen peroxide
Filter paper discs
Forceps
Stopwatch
Syringe
Distilled water
Paper towel

30
Q
A
31
Q

4 - Investigation into the effect of enzyme or substrate concentration
on enzyme activity

Method

A
  1. Grind a 2cm piece of potato cylinder with 5cm3
    of distilled water to make a smooth
    paste containing the enzyme.
  2. Place 10cm3 of H2O2 in a specimen tube/ test tube.
  3. Using forceps, dip a filter paper disc into the enzyme suspension, tap off the excess.
  4. Drop the filter paper disc into the hydrogen peroxide solution and measure the time,
    to the nearest second, that it takes from striking the surface to sink to float up to the
    surface again.
  5. Remove the disc from the tube using forceps and discard

1. Biology A-level (9 decks)

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