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Question 1

The student was given a 1.0moldm–3 sucrose solution.
State how the student used this solution to make a 0.8moldm–3 sucrose solution.
(1)

Answer 1

use ratio of 8:2 of sucrose and water

Question 2

The method used by the student could be improved to obtain a more accurate
value for the water potential of these potato cells.
Justify three improvements that could be made.

(3)

Answer 2

 control temperature because affects
{diffusion / osmosis / molecular movement / membrane permeability} (1)

 submerge cubes in sucrose solution so all surfaces in contact (1)

 use smaller intervals of sucrose concentration (between 0.2 and 0.4) (1)

 blot cubes before weighing to remove surface solution /
blot cubes dry to remove excess solution (1)

 repeat to identify {anomalies / variability / SD} /
because result in table could be {anomalous} (1)

Question 3

The student used a paintbrush to obtain pollen grains from a flower.

Describe the steps taken by the student to see these pollen grains using a microscope.

(3)

Answer 3

 pollen grains put in
{water / sugar / sucrose / mineral ions / glycerol} solution (1)
 use of a (microscope) slide / cavity slide / use a coverslip (1)
 use low power lens first / use increasing magnification

Question 4

Why calculate SD

Answer 4

-shows variation from the mean

 therefore gives an indication of significant difference /overlap gives indication of significant difference (1)

Question 5

State how an action spectrum and an absorption spectrum show that

chlorophyll is used in photosynthesis.

(1)

Answer 5

spectra are similar / spectra overlap

Question 6

The scientist used the following steps in the method.
Step 1: plants were grown in darkness for one week to produce yellow leaves
Step 2: leaf discs of the same diameter were taken from the first pair of these leaves
Step 3: a total of 25 discs was put into tubes containing different cadmium chloride concentrations
Step 4: these tubes were kept at 27°C and exposed to
the same source of light

Justify the method used by the scientist.

(5)

Answer 6

 grown in darkness for a week so leaves big enough to obtain discs / wsso leaves contain {less / no pigment} (1)
 discs same {diameter / leaves / leaf age} because affects pigment concentration} (1)
 25 discs used so that sufficient pigment obtained / calculate SD (1)
 {control / 0.0} solution allows comparison (1)
 same temperature as it affects enzymes (1)
 same light {wavelength / source / intensity} as light affects synthesis of pigments (1)
 48 hours allows time for pigment synthesis

Question 7

Explain why it was important to measure the volume of oxygen in the first 10 seconds.
(2)

Answer 7

-it is the initial rate of reaction (1)#

most accurate representation of rate as

-substrate is in excess / not limiting /

Question 8

The students used the following method.
● a burette filled with water is placed in a beaker containing water
● add hydrogen peroxide to the conical flask
● open the conical flask and drop 0.1g of raw liver into the hydrogen peroxide
● replace the bung on the conical flask
● after 10 seconds pinch the rubber tube to stop any more oxygen entering the burette
● measure the volume of oxygen collected in the burette
● repeat this method for boiled liver

Give four possible improvements to the method used by these students that
would reduce the variability of the results.

(4)

Answer 8

 use liver with same surface area to volume ratio (1)
 control temperature (1)
 control {volume / concentration} of hydrogen peroxide
 replace bung quickly (1)
 use gas syringe to collect oxygen (1)

Question 9

How to answer comparisons on peercentage cover distribution graphs

Answer 9

One from similarities:
 neither found at specified point
 both found between at specified point

One from differences:
one found closer other further
 range for this one is bigger than for that one
 maximum percentage cover of this one is greater than that one

Question 10

The student measured the water content of the soil from the high water line to
170m inland.
Describe how the student could have carried out these measurements.

(3)

Answer 10

sample at intervals along transect /
sample from same place in quadrat (1)
 insert probe into the soil (1)
 at same {depth / length of time}

Question 11

Describe how soya bean plants can be genetically modified to produce large numbers of GM soya bean plants.

(4)

Answer 11

 use of restriction enzyme to cut {gene / DNA / allele / plasmid} (1)
 use of ligase to insert / join {gene / DNA / allele} (1)
 use of vector (1)
 use of plasmid / Agrobacterium / gene gun / virus / electroporation /
microinjection (1)
 use of cloning (1)

Question 12

Explain how a student could modify this respirometer and use it to measure the mean oxygen consumption of a rat.

(4)

Answer 12

 use {soda lime / KOH / NaOH} to absorb carbon dioxide (1)
 put {water / dye / ink} (1)
 use ruler / scale to measure distance (1)
 use {syringe / cross sectional area multiplied by distance / use πr2d}
to measure volume of oxygen (1)
 use {syringe / 3-way tap} to reset / do repeats (1)
 control temperature using water bath (1)