The answers :D

1 (a) (i) one cell drawn (at high power), two lines for cell wall;

correct cell structure and cell wall and nucleus labelled correctly;
Ignore low power. Reject two or more cells together.
Rej. if have additional organelles mitochondria, chloroplasts, Golgi. [2]
Present your observations from the slides made from distilled water, T1 and T2
1 (a) (ii)
Either
single table, all cells drawn, column headings: solution/slide/(distilled) water/W and T1 and T2;
to left/across top, observations/feature/e.g. to right/ underneath/clear what is recorded in the boxes;
T1 cell membranes/cytoplasm pulled away from cell wall/plasmolysed;

T2 granules/particles in cell/more plasmolysed/destroyed/stained/coloured
e.g. brown/black/AW;
Or when only drawings given three drawings, labelled (distilled) water/W, T1 and T2;
clear that cell walls and cell membranes are all different (for water, T1 and T2);

T1 cell membranes/cytoplasm pulled away from cell wall/plasmolysed;
T2 granules/particles in cell/more plasmolysed/destroyed/stained/coloured e.g. brown/black/AW;


No outer boundary needed for table.



Reject cells shrink or become smaller.
Accept vacuole shrinking or drawn.
Allow any description that cells have been destroyed/cell membranes ruptured/disorganised/ leakage of cell.
Reject cell walls broken down.
[4]
Explain observations from water, T1 and T2.
1 (a) (iii)

Idea of
1. high/less negative water potential to lower/more negative water potential/down water potential gradient
Any two of:
2. (in water)idea of water has moved in/no net movement;
3. (in T1/T2) idea of water has moved out;
4. (in T2/lead nitrate) killed/destroyed cells/toxic/effect described/AW;
AND by osmosis at any point;
In correct context.
Accept ψ.
Solute/osmotic potential is ignored but must be the same as water potential i.e. from high to low,
so reject pt1 if wrong way.
Ignore hypotonic and hypertonic but must be in correct context if used.

Must be correct with the candidate’s own results.
Reject cell wall destroyed.
[1]


[2 max]
1 (a) (iv) Two from
evaporation from solutions/concentration of solution changes;
cells left different lengths of time/too short a time/not long enough;
AVP; volume/no. of drops used; or
different or different onions/parts of onion/not fresh/have been frozen/stored;

Reject not immersed.

Reject should be same
time –not an error.
Reject amount.
Mark for any correct.

Reject improvements.
[2 max]


Suggest how you could modify the experiment to investigate the effect of lead nitrate. 3 ACE improvements
1 (b)

more/serial dilution concentrations of lead nitrate;
Then any TWO from
at least 3 specified lead nitrate concentrations;
repeat each concentration/more than one strip (per concentration);
keep the time the same/give an example of a time/longer time;
keep the volume AND method /use graduated pipette/no.of drops the same/AW;
same onion/same part/fresh;
detailed measurement method/use of eyepiece graticule to measure plasmoylsed
cells/count number of plasmolysed cells in a sample of 20 or more;
Reject shorter time.
[1]


[2 max]
Complete the Table 1.2 by calculating the missing values PDO display
1 (c) (i) 6,81; A whole numbers only and both correct [1]
Plot a graph of concentration of sodium chloride against the percentage plasmolysis of the cells PDO layout
1 (c) (ii)

[3]

x-axis conc, mol dm –3/M or molar/mole(s)/l or per litre AND y-axis percentage/% plasmolysis; Rej. mol/dm–3 and mol dm 3.
[1]
scale as shown/y axis 25 to 2cms, allow no 0 marked AND plotting crosses or dot in circle ONLY AND 0.0, 0.2
and 0.6 and1.0 plotted correctly;
no larger then X or O plots 0.2 must be on horizontal line,
0.2 and 0.6 and 1.0 between the horizontal lines.
Ignore incorrect calculated mean plots i.e. 0.4 and 0.8.
Rej. blobs in or out of
circle.
[1] either ruled lines joining each point or smooth curve through 0; no thicker than

no feathery line, line must
go to 0
Rej. any extrapolation
beyond either axis.
[1]
State concentration at which 50% plasmolysis occurred 1 ACE interpretation
1 (c) (iii) take reading from candidates own graph, AND must have units; Allow two decimal places. Ecf units from graph. [1]
‘The more concentrated the solution the more plasmolysed the cells become’ draw
conclusion include whether the data support the hypothesis and produce a revised
hypothesis if necessary
1 (d) General statement :
Either support or no support or partial support for the hypothesis or writes a
conclusion which states the hypothesis;
quotes 2 sets of figs. with both axes; OR
idea that up to 0.4 /low concentration only small % plasmolysed/or % plasmolysis
does not increase evenly with increasing concentration/or levels off at high
concentration;

Needs clear statement.
Reject supports conclusion.

Idea of correct relationship may quote figures to
get same idea.

Reject all/100% plasmolysed. [2]

2 (a) (i) sharp, clear unbroken lines, height no more than two thirds the length ;
no cells, no shading, larger than 6 cm in any direction;
at least three lines (plus very thin inner layer if shown);
uneven all the way round and one solid inner line;
Outer two lines only

No more than 2 errors.
Actual = 5.5 cm to 9 cm.
[4]

2 (a) (ii) Each division on stage scale is 0.1 mm = V
First mark
Reject any measurements given for mark points 1 and 2. Accept units or divisions.
First Mark No. of eyepiece grat. W
Second Mark No. of eyepiece grat. Y
No on stage micrometer Z
Third Mark Show logical reasoning EITHER
Z divided by Y first,
then proceed and allow multiplication by either V
and then W, or W and then V, even though not
strictly the correct reasoning.
Ignore answer and units.
Rej. if additional figs. even if x1.
OR
Z x V AND divided by Y. followed by x W

Ignore answer and units.
Rej. if additional figs. even if x1.
Fourth Mark Need NOT be the correct
answer
Either between 100 and 999 with µm
Allow standard form if correct. Reject metres.
OR answer between 0.1 and 0.99 with mm;
Allow standard form if correct. Reject metres.
First two marks are for – collecting the correct data. The third mark is for display – showing clear reasoning in the calculation.
Fourth mark is for recording – use of the correct units.
[4]
P/S PLEASE COMPARE RESULTS WITH CLASSMATES!!!TQ


Suggest how an error in measuring the lumen could occur
2 (a) (iii) not knowing where edge is/lumen irregular shape/preparation squashed/only 1
measurement/thicknesses of lines(stage micrometer)/between divisions on
eyepiece graticule/one scale line is not at edge of lumen/focussing of both
scales/lining up the scales;
Ignore parallax error
[1]
Compare and contrast specimens Fig. 2.4 and 2.5. 2
2 (b) (i)
organised as a table/Venn diagram/ruled boxes connected, correctly headed;
comparative statements opposite each other;

both have lumen/central space;
lumens larger, smaller;
number (lumen/tubes) single/one, more/lots;
cells /cell walls/end
walls
none/absent, present;
bands absent/none present;
Ref. pits/circles/spots none, present;
Must have at least one similarity.




Accept tubes/vessels as alternative to lumen.
Reject ref. to Fig. 2.4 having cells – not visible.

Reject uses
Rej. ref. lignin/cellulose with walls or bands.

[5]

Suggest one feature which indicates the Fig 2.5 is a plant \
2 (b) (ii) have cell walls/xylem/phloem/sieve tube (element)/companion cell/pits/rings; Ignore cellulose, lignin, vessel on own.
Reject sieve plates. [1]
Make a labelled drawing of 5 representative cells. 1 MMO collection, 3 MMO decisions
2 (b) (iii) 5 shown on Fig.;
drawn 3 diverse cells;
3 different sizes;
at least 1 cell drawn with bands/parts of
bands/pits;



AND longer than wide;
Reject point 1 if more than 5
marked or drawn.
Entire cells or open tubes.
Ignore labels.
Reject points 2, 3 and 4
if more than 2 TS or
textbook.
Max 1 point, 1 only
[1]


[3]


PS: credits to eng kee for this :D