Question 1:-
Read the passage below. Use the information in the passage and your own knowledge to answer the questions that follow.
Tissue culture and plants
In micropropagation, plant tissues are grown in vitro on plant tissue culture media, under aseptic conditions in a controlled environment. This technique is possible because plant cells can differentiate and become specialised cells. This allows them to change their metabolism, growth and development to form a whole plant.
5 Plant tissue culture media contain substances to support the normal growth and development of plants. The media are mainly composed of minerals, vitamins, and plant hormones. The pH of the media is kept constant.
10 Plant hormones play an essential role in determining how cells and tissues develop in culture media. Plant cells can differentiate into different tissues and cell types.
The concentration of hormones can determine the tissue that develops. Auxins and cytokinins are the most widely used. A balance of both auxin and cytokinin leads to the development of a mass of undifferentiated cells known as a callus.
15 In vitro cell culture offers an alternative method for conserving endangered species and varieties. Tissue culture can be used when the plant species produce seeds that do not germinate or have seeds that cannot be stored for a long period of time. These can be successfully preserved using in vitro techniques for the maintenance of gene banks.
20 Embryo culture is a type of plant tissue culture that is used to grow embryos from seeds in nutrient media. In embryo culture, the plant develops directly from the embryo or indirectly through the formation of a callus and then subsequent formation of shoots and roots. The technique has been developed to break dormancy in seeds, and to reproduce rare species and haploid plants.
Scientists are also using cell suspension culture systems from which products can be extracted. A suspension culture is developed by transferring a portion of the callus into liquid media. The media are maintained under suitable conditions of agitation,
light and temperature. This system can provide a continuous, reliable source of natural products independent of climate and soil conditions. The first commercial application of large‐scale suspension cultivation of plant cells was carried out to produce shikonin. Shikonin is used in traditional Chinese medicine and is a potential anti‐cancer treatment.
(a) State what is meant by the term in vitro. (line 1)
(b) Explain how plant cells differ from human cells in their ability to differentiate and specialise. (lines 2 and 3)
(c) Give the function of two named minerals included in the culture media. (line 6)
1 …………………………………………………………………………..
2 …………………………………………………………………………..
(d) Explain why the pH of the media needs to be kept constant. (line 7)
(e) Auxin also controls the response of plants to light.
Describe a simple experiment you could do to show the phototropic response of plant stems to light.
(f) Explain why scientists want to conserve endangered plant species and varieties. (lines 13 and 14)
(g) Explain why plant cell suspension culture media are maintained under suitable conditions of agitation, light and temperature. (lines 24 and 25)
▶️Answer/Explanation
Ans : 1(a) • in a test tube / culture dish / jar / glass / petri dish / container / in culture solution / in a lab / outside a living organism / eq (1)
1(b) An explanation that makes reference to the following points:
• plant cells can differentiate / eq (1)
• into all / different types / kinds of tissues or cells / specialised cells eq (1)
• throughout the plants life / eq (1)
• can form / regenerate (whole) new plant / eq(1)
allow converse for human cells
only stem cells can
only embryonic
1(c) An explanation that makes reference to the following points:
• mineral 1 (1)
• function (1)
• mineral 2 (1)
• function (1)
allow for eg
named minerals to get function mineral must match no mineral no function
not just for growth
nitrate amino acids / proteins / DNA/ nucleic acids /eq
Magnesium chlorophyl / chloroplasts / photosynthesis
Phosphate ATP / DNA / RNA / nucleic acids / cell membranes/ eq
Calcium cell wall / cell membranes / eq
Potassium stomatal opening / eq
allow other correct mineral ions
ignore nitrogen / nitrites / phosphorous /
1(d) An explanation that makes reference to two of the following points:
• enzyme affected by pH / by acid / by alkali / works best at optimum (1)
• shape of active site changed / substrate can no longer bind / fit / eq (1)
• enzyme / active site denatured (1)
to score mp 1 must mention enzymes somewhere in answer
1(e) A description that makes includes three of the following points:
• (shoot) in light from one side / unidirectional light / eq (1)
• (shoot) in darkness / light all around / light from other side / eq (1)
• leave for both for stated time / use shoots of same type / same temperature / same water / other control variable / eq (1)
• description of bending or growing towards light or measure angle / look at curve / bending / eq (1)
allow leave for a few days
1(f) An answer that makes reference to two of the following points:
• maintain biodiversity / reduce damage to food chains / ecosystems / eq (1)
• prevent extinction (1)
• keep (species / varieties / genotypes) for future generations / future use / eq (1)
• in case climate changes / eq (1)
• for medicinal properties / eq
ignore increase biodiversity
1(g) An explanation that makes reference to three of the following points:
• (agitation) to mix contents / m i x m e d i a / m i x oxygen / mix carbon dioxide (with plant cells) / substrates with plant cells / take up minerals / take up nutrients / eq (1)
• (light) for photosynthesis / eq (1)
• (suitable temperature) for enzyme action / eq (1)
Question 2:-
The diagram shows two cells from a plant root.
(a) (i) Which structure is the vacuole?
A F
B G
C H
D I
(ii) Which structure is the nucleus?
A F
B G
C H
D J
(b) The actual length of the root cell from P to Q is 80μm.
Determine the magnification of the diagram.
[1000μm = 1mm]
magnification =×……………………………………………………..
(c) Root hair cells are specialised cells adapted for their functions.
Explain how root hair cells are adapted for their functions in the plant.
▶️Answer/Explanation
Ans :2(a)(i) The only correct answer is D (I is the vacuole)
A is not correct as F is the cell wall
B is not correct as G is the nucleus
C is not correct as H is the cytoplasm
2(a)(ii) The only correct answer is B (G is the nucleus)
A is not correct as F is the cell wall
C is not correct as H is the cytoplasm
D is not correct as J is a mitochondrion
2(b) correct measurement of P to Q conversion to μm division of PQ ÷ actual length correct answer = 475 (3)
allow 450-500 for 3 marks allow in standard form ( 4.75 x 102)
allow 36-40 mm or 3.6 to 4.0 cm for correct measurement with units 1 mark and 1 m a r k for ÷ 80
2(c) An explanation that makes reference to four of the following points:
• long (root hair) / reaches into soil / penetrates / branches / eq (1)
• increases surface area (1)
• to absorb water / eq (1)
• by osmosis (1)
• to absorb minerals / ions / eq
• by diffusion (1)
• active transport (1)
protuberance
Question 3:-
The picture shows two biscuits, A and B.
The table shows some nutritional information supplied by the manufacturers of the two biscuits.
(a) Calculate the percentage of the total carbohydrate in biscuit A that is starch.
percentage = ……………………………………………………..%
(b) A doctor has advised a person to lose weight.
Comment on which biscuit, A or B, would be most suitable for the person to maintain a healthy diet and to lose weight.
Use the information in the table and your own knowledge in your answer.
(c) A teacher tells some students to carry out an experiment to compare the energy values of biscuit A and biscuit B.
(i) Describe a suitable method the students could use for their experiment.
(ii) The energy values the students determined for the biscuits were much lower than the energy values supplied by the manufacturers.
Give two reasons why this is the case.
1 …………………………………………………………………………..
2 …………………………………………………………………………..
▶️Answer/Explanation
Ans : 3(a) mass of starch ÷ mass of carbohydrate × 100 98% (2)
allow 1 mark for ÷ 68
allow 97.8 / 97.79 / 97.794 etc for 2 marks
3(b) An answer that that makes reference to four of the following points:
biscuit B , difference and explanation
1. less energy/ kJ so less stored as fat / less weight gain / stored fat used for energy / eq (1)
2. less lipid / so less (energy) stored as fat / less weight gain / less blood cholesterol / less risk of CHD / eq (1)
3. less sugar / so less (energy) stored as fat / less weight gain / less risk of diabetes / eq (1)
4. more starch so energy released (more) slowly / eq (1)
5. less salt so less effect on blood pressure / less risk of CHD/ eq (1)
6. more protein for repair / growth / eq(1)
allow converse for biscuit A
if no reason and explanation allow one max for biscuit B and correct difference(s)
not just to lose weight
3(c)(i) A description that makes reference to four of the following points:
1. measure out cm3 / same volume / measure mass of water / eq (1)
2. use sample of biscuits of same mass / known mass / eq (1)
3. hold under boiling tube of water /eq (1)
4. relight if goes out / continue until completely burnt / eq (1)
5. (use thermometer to) measure increase in water temperature / measure initial and final temperature of water/ eq (1)
6. highest temperature rise / ref to equation has most energy / eq (1)
allow mp 1 2 5 6 from equation
energy = (mass of water x temp rise x 4.2) ÷ mass of biscuit
3(c)(ii) An answer that includes two of the following
• some energy lost / some heat escapes / (to surroundings) / not all energy reaches tube / some released as light /eq (1)
• not completely burnt / not all energy released / not burnt in oxygen / eq (1)
• temperature of water uneven / eq (1)
Question 4:-
The diagram shows the nitrogen cycle. Some of the stages have been labelled.
(a) (i) Which stage shows nitrogen fixation?
A P
B Q
C T
D V
(ii) Which stage shows nitrification?
A Q
B U
C T
D W
(iii) Which stage shows denitrification?
A P
B T
C V
D W
(b) Farmers sometimes add chemical fertiliser to the soil.
(i) Describe how pollution by fertiliser can affect aquatic ecosystems.
(ii) Give an alternative to chemical fertiliser that a farmer could use.
▶️Answer/Explanation
Ans : 4(a)(i) The only correct answer is A (P is nitrogen fixation)
B is not correct as Q is not nitrogen fixation
C is not correct as T is not nitrogen fixation
D is not correct as V is not nitrogen fixation
4(a)(ii) The only correct answer is C (T is nitrification)
A is not correct as Q is not nitrification
B is not correct as U is not nitrification D is
not correct as W is not nitrification
4(a)(iii) The only correct answer is D (W is denitrification)
A is not correct as P is not denitrification
B is not correct as T is not denitrification
C is not correct as V is not denitrification
4(b)(i) A description that that makes reference to five of the following points:
1. increase in nitrates / phosphates/ eq (1)
2. eutrophication (1)
3. algal bloom / more algae / plants grow on surface / eq (1)
4. blocks sunlight / prevents photosynthesis /eq (1)
5. plants die / algae die / eq (1)
6. bacteria decompose / bacteria respire / microorganisms decompose / microorganisms respire /eq (1)
7. oxygen depleted / oxygen used (in respiration) / oxygen required (for respiration) / eq (1)
8. fish / aquatic organisms / die /eq (1)
4(b)(ii) • animal manure / dung / faeces / animal waste / eq (1)
Question 5:-
(a) Diagram 1 shows part of a DNA molecule.
(i) Complete Diagram 1 by writing the letters of the missing bases in the empty boxes for strand 2.
(ii) Give the maximum number of amino acids that are coded for by this DNA strand (strand 2).
(iii) The original DNA strand is used to produce mRNA.
Complete the empty boxes in Diagram 2 to show the mRNA coded for by this DNA strand.
(b) A length of DNA consists of 25000 base pairs.
This makes a total of 50000 bases.
In this length of DNA, 30% of the bases are adenine (A).
Determine the number of thymine (T) bases, cytosine (C) bases, and guanine (G) bases in this length of DNA.
number of thymine bases (T) = ……………………………………………………..
number of cytosine bases (C) = ……………………………………………………..
number of guanine bases (G) = ……………………………………………………..
(c) Describe the differences between the process of transcription and the process of translation.
▶️Answer/Explanation
Ans : 5(a)(i) C C G A T C A A C
all correct 2 marks one letter incorrect 1 mark
5(a)(ii) 3 (1)
5(a)(iii) C C G A U C A A C
all correct 2 marks one letter incorrect 1 mark
5(b) 30 % of 50 000 so 15 000 are A and 30 % are T 15 000
leaving 20 000 bases 40% (30 % are) T 15 000 (1) (20% will be) C 10 000 (1) (20% will be) G 10 000 (1)
allow 2 marks if put % in correctly instead of numbers
so 30% T
20% C
20% G scores 2 marks
5(c) A description that includes:
Transcription
Location
• transcription in nucleus / eq(1)
Produces
• transcription produces mRNA/ e q (1)
Starts with
• transcription starts with DNA /eq (1)
Uses
• no tRNA in transcription /eq (1)
or converse for
Translation
takes place in cytoplasm / ribosome mRNA exits nucleus / enters cytoplasm/eq
produces amino acid chain / polypeptide / protein/eq
starts with mRNA /eq
(so transcription) from DNA to mRNA = start and produces = 2 marks
uses tRNA/eq
Question 6:-
Smoking cigarettes has harmful effects on the body.
Graph 1 shows the number of hospital admissions in thousands due to conditions caused by smoking each year from 2009 to 2019.
(a) Using information from Graph 1, calculate the percentage increase in the number of hospital admissions caused by smoking in 2019 compared with 2009.
percentage increase = ……………………………………………………..%
(b) Graph 2 shows the percentage of all hospital admissions that were due to conditions caused by smoking each year from 2009 to 2019.
Comment on the changes in the number of hospital admissions caused by smoking and the percentage of all hospital admissions that were caused by smoking.
Use data from graph 1 and graph 2 in your answer.
(c) Smoking causes harmful effects on the lungs.
Describe the consequences of smoking cigarettes for the functioning of the lungs.
▶️Answer/Explanation
Ans : 6(a) number at 2009 = 462 000
number at 2019 = 506 000
change = 506-462 = 44
% change = (44 ÷ 462) × 100 = 9.52 % / 9.5%/ 9.524% / 9.5238 %/ etc (2)
allow 1 for 44
allow full marks for 9.52 / 9.524 / 9.5238 with no working
6(b) An answer that makes reference to four of the following points:
1. number of admissions due to smoking increased (2009 to 2019) /eq (1)
2. number of admissions due to smoking level / little change from 2009 to 2012 / eq (1)
3. number of admissions due to smoking decreased from 2012 to 2013 / least in 2013. (1)
4. but % / proportion of all admissions due to smoking declined / lowest in 2019 / eq (1)
5. as other admissions increased / other illnesses / diseases becoming more frequent / eq (1)
6. smaller percentage of people (started) smoking / greater percentage people stopped / eq (1)
7. population size increases / eq (1)
8. reliable / valid data / covers large numbers / all admissions / long period of time / eq (1)
From Graph 1
must have date ref
From Graph 2
fewer people smoking / smoking habits change people using alternatives e cigarettes
6(c) A description that makes reference to five of the following points:
1. destroys cilia in trachea / cilia no longer function / eq (1)
2. mucus builds up / cannot be removed /eq (1)
3. leads to (bacterial) infection (of alveoli) /pneumonia / eq (1)
4. loss of surface area / loss of / damage to alveoli /emphysema / eq (1)
5. airways inflamed or narrowed / bronchitis / eq (1)
6. can lead to COPD (1)
7. (lung) cancer (1)