AQA A LEVEL BIOLOGY 7402/3 PAPER 3 QUESTION PAPER AND MARK SCHEME { MERGED} JUNE 2023 COMP, Exams of Biology

Download AQA A LEVEL BIOLOGY 7402/3 PAPER 3 QUESTION PAPER AND MARK SCHEME { MERGED} JUNE 2023 COMP and more Exams Biology in PDF only on Docsity! AQA A LEVEL BIOLOGY 7402/3 PAPER 3 QUESTION PAPER AND MARK SCHEME { MERGED} JUNE 2023 COMPLETE AND VERIFIED Please write clearly in block capitals. BIOLOGY Paper 3 Wednesday 21 June 2023 Morning Time allowed: 2 hours Materials For this paper you must have: • a ruler with millimetre measurements • a scientific calculator. Instructions • Use black ink or black ball-point pen. • Fill in the boxes at the top of this page. • Answer all questions in Section A. • Answer one question from Section B. • You must answer the questions in the spaces provided. Do not write outside the box around each page or on blank pages. • If you need extra space for your answer(s), use the lined pages at the end of this book. Write the question number against your answer(s). • Show all your working. • Do all rough work in this book. Cross through any work you do not want to be marked. Information • The marks for the questions are shown in brackets. • The maximum mark for this paper is 78. For Examiner’s Use Question Mark 1 2 3 4 5 6 7 TOTAL Centre number Candidate number Surname Forename(s) Candidate signature I declare this is my own work. A-level 4 Do not write outside the 0 2A student investigated the effect of different sugars on the rate of respiration in yeast. Yeast normally respires glucose. Figure 2 shows the method she used for her first experiment. Figure 2 0 2 . 1 Other than those stated, suggest two variables the student needed to keep constant in her investigation. box [1 mark] 1 2 *04* IB/M/Jun23/7402/3 5 Do not write outside the Figure 3 shows the result she obtained for yeast in glucose solution. Figure 3 box 2 Use Figure 2 and Figure 3 to calculate the rate of carbon dioxide production in mm s –1 for yeast in glucose solution. Give your answer in standard form and to 2 significant figures. Show your working. [2 marks] Answer mm s–1 *05* Turn over ► IB/M/Jun23/7402/3 2 . 0 6 Do not write outside the 3 The student repeated the experiment using yeast in maltose solution. She found the rate of carbon dioxide production was slower than with yeast in glucose solution. Suggest why. box [2 marks] 4 A second student used a different method to investigate the effect of different sugars on the rate of respiration in yeast. He set up a tube with yeast in glucose solution and added bromothymol blue. Bromothymol blue changes from blue to yellow when carbon dioxide is produced. To determine the rate of respiration, he timed how long it took for the solution to change from blue to yellow. Suggest: • why the method the second student used would be less accurate than the method the first student used • how the accuracy of the method the second student used could be improved. [2 marks] This method would be less accurate because The accuracy of this method could be improved by *06* IB/M/Jun23/7402/3 2 . 0 2 . 0 9 Do not write outside the Table 1 box Plate Number of colonies of bacteria with with with chloramphenicol novobiocin no antibiotic 1 2 238 276 2 4 263 258 3 6 261 324 2 Calculate the mean number of bacteria in the undiluted bottle of liquid culture containing novobiocin. Give your answer in standard form. Show your working. [2 marks] Answer bacteria 3 Starting with a single bacterium, calculate how many generations it would take to produce at least the number of bacteria you have calculated for your answer in Question 03.2 You can assume no bacteria die. You could use the ln or log button on your calculator to calculate your answer. [1 mark] Answer generations Question 3 continues on the next page *09* Turn over ► IB/M/Jun23/7402/3 3 . 0 3 . 0 10 Do not write outside the 4 M. luteus is not resistant to chloramphenicol. Suggest two reasons why the bacteria were able to grow in the culture containing chloramphenicol. box [2 marks] 1 2 *10* IB/M/Jun23/7402/3 3 . 0 6 11 *11* Turn over for the next question DO NOT WRITE ON THIS PAGE ANSWER IN THE SPACES PROVIDED Do not write outside the box Turn over ► IB/M/Jun23/7402/3 14 0 4 . 3 Nine days after transplantation, the c-KIT+ group showed that 68% of infarcted tissue was made up of new cardiomyocytes. The control group had no new cardiomyocytes. Assuming that mean ventricular blood pressure is directly proportional to the number of cardiomyocytes, calculate the percentage of infarcted tissue that was made up of new cardiomyocytes in the c-KIT– group. Do not write outside the box [2 marks] Answer % All new cardiomyocytes produced: • Connexin-43, a channel protein that allows electrical impulses to pass between cardiomyocytes • GATA-4, a transcriptional factor that stimulates the expression of genes for actin and myosin. 4 Suggest how production of Connexin-43 and GATA-4 could give the result seen in the c- KIT+ group in Figure 6 (on page 13). Do not include details of transcription or translation in your answer. [2 marks] Connexin-43 GATA-4 *14* IB/M/Jun23/7402/3 4 . 0 10 15 *15* Turn over for the next question DO NOT WRITE ON THIS PAGE ANSWER IN THE SPACES PROVIDED Do not write outside the box Turn over ► IB/M/Jun23/7402/3 16 0 5Scientists investigated the effect that the release of heated water into a river from a power station had on the biodiversity of a local fish community over 29 years. They measured the species richness and the number of fish of each species at the same site in October every year. The scientists used this information to calculate an index of diversity (d) of fish for each year. Figure 7 and Figure 8 show their results. Figure 7 Figure 8 Do not write outside the box *16* IB/M/Jun23/7402/3 19 *19* Turn over for the next question DO NOT WRITE ON THIS PAGE ANSWER IN THE SPACES PROVIDED Do not write outside the box Turn over ► IB/M/Jun23/7402/3 20 1Give two types of cell that can stimulate an immune response. [2 marks] Do not write outside the box 1 2 An autoimmune disease causes the immune system to attack healthy body tissues. Scientists investigated the immune responses of healthy mice and mice with autoimmune disease. The chemical OXA causes an immune response in mice and can make their skin swell. Mice had olive oil applied to their left ear and OXA in olive oil applied to their right ear. The immune response was recorded in two ways: • the cellular response by measuring the mean increase in ear thickness 24 hours after exposure to OXA • the humoral response by measuring the mean concentration of anti-OXA antibody in blood 14 days after exposure to OXA. Table 2 shows the results of this investigation. The values in the brackets show ± 2 standard deviations. A value of ± 2 standard deviations from the mean includes over 95% of the data. Table 2 Type of mice Sex of mice Mean increase in ear Mean concentration thickness / cm × 10 –3 of anti-OXA antibody / arbitrary units Healthy Male 17.9 (±4.1) 16 (±3) Female 18.5 (±2.9) 14 (±4) Autoimmune Male 25.9 (±4.5) 14 (±2) disease Female 16.7 (±3.0) 26 (±7) 2 Suggest and explain one reason why olive oil was applied to the left ear of the mice. [1 mark] *20* IB/M/Jun23/7402/3 6 . 0 6 . 0 21 3 Plot a suitable graph for mean increase in ear thickness for each group of mice in Table 2. Include the data for ± 2 standard deviations on your graph. Do not write outside the box [3 marks] Question 6 continues on the next page *21* Turn over ► IB/M/Jun23/7402/3 6 . 0 24 Do not write outside the 6 In mice, one type of autoimmune disease is inherited as a dominant allele. Would the Hardy–Weinberg principle hold true for a population of mice, some of which had this autoimmune disease? Explain your answer. box [2 marks] *24* IB/M/Jun23/7402/3 6 . 0 15 25 Do not write outside the Section B Answer one question. You are advised to spend no more than 45 minutes on this section. box ite an essay on one of the topics below. Either . 1 The importance of interactions between organisms and their environment. [25 marks] Or *25* 2 The importance of membranes in the functioning of cells. [25 marks] Turn over ► IB/M/Jun23/7402/3 7 . 0 7 0 7Wr 0 26 Do not write outside the box *26* IB/M/Jun23/7402/3 28 Do not write outside the box *28* IB/M/Jun23/7402/3 29 D o n o t w ri t e o u t s i d e t h e b o x *29* Turn over ► IB/M/Jun23/7402/3 *31* Turn over ► IB/M/Jun23/7402/3 32 Do not write outside the box *32* IB/M/Jun23/7402/3 33 D o n o t w ri t e o u t s i d e t h e b o x 35 Do not write outside the box END OF QUESTIONS *35* IB/M/Jun23/7402/3 25 36 There are no questions printed on this page DO NOT WRITE ON THIS PAGE ANSWER IN THE SPACES PROVIDED Do not write outside the box *36* IB/M/Jun23/7402/3 37 *37* Do not write outside the box IB/M/Jun23/7402/3 Question number Additional page, if required. Write the question numbers in the left-hand margin. 40 There are no questions printed on this page DO NOT WRITE ON THIS PAGE ANSWER IN THE SPACES PROVIDED Do not write outside the box A-level BIOLOGY 7402/3 Paper 3 Mark scheme June 2023 Version: 1.0 Final *236A7402/3/MS* MARK SCHEME – A-LEVEL BIOLOGY – 7402/3 – JUNE 2023 Mark schemes are prepared by the Lead Assessment Writer and considered, together with the relevant questions, by a panel of subject teachers. This mark scheme includes any amendments made at the standardisation events which all associates participate in and is the scheme which was used by them in this examination. The standardisation process ensures that the mark scheme covers the students’ responses to questions and that every associate understands and applies it in the same correct way. As preparation for standardisation each associate analyses a number of students’ scripts. Alternative answers not already covered by the mark scheme are discussed and legislated for. If, after the standardisation process, associates encounter unusual answers which have not been raised they are required to refer these to the Lead Examiner. It must be stressed that a mark scheme is a working document, in many cases further developed and expanded on the basis of students’ reactions to a particular paper. Assumptions about future mark schemes on the basis of one year’s document should be avoided; whilst the guiding principles of assessment remain constant, details will change, depending on the content of a particular examination paper. Further copies of this mark scheme are available from aqa.org.uk MARK SCHEME – A-LEVEL BIOLOGY – 7402/3 – JUNE 2023 Question Marking Guidance Mark Comments 01.1 1. (There are) stretch-mediated sodium ion 1. 2. 3. or 4. Accept channels (in the membrane); Na + 2. (Increased pressure) deforms/changes Max 2 if only (sensory neurone/axon) membrane/lamella(e) reference to sodium OR 3 max and not sodium ions (Increased pressure) deforms/changes sodium (3 x ion channels; AO1) 3. Sodium ion channels open; 4. Accept sodium ions move in down 4. Sodium ions diffuse in; a concentration gradient 5. Depolarisation (leading to generator potential); 5. Accept inside becomes positive Question Marking Guidance Mark Comments 01.2 1. An action potential is only generated/produced 1. Ignore any when threshold is reached numbers linked to threshold OR 1. and 2 Accept impulse for action An action potential is not generated/produced potential until/unless threshold is reached; 2. When high pressure was applied (to the 2 2. Accept references fingertip), threshold was reached (1 x to ‘the first peak’ AO1, 1 for high pressure OR x AO3) 2. Accept the High pressure is (an) above threshold converse for low pressure (stimulus) OR High pressure generates an action potential; Question Marking Guidance Mark Comments 01.3 (The) refractory (period); Ignore any reference 1 to absolute or relative (AO1) Reject refraction period 5 MARK SCHEME – A-LEVEL BIOLOGY – 7402/3 – JUNE 2023 Question Marking Guidance Mark Comments 02.1 Accept any two of the following for one mark: Ignore number of yeast cells Ignore amount for Concentration/mass of yeast volume or Concentration/mass of glucose/sugar (solution/s) concentration Concentration of oxygen (in solution) 1 Volume of yeast (AO3) Volume of glucose/sugar (solution/s) pH (of glucose/sugar solution/s) Species/type of yeast Size/diameter/volume of test tubes Question Marking Guidance Mark Comments Correct answer of 2.5 x 10 –2 = 2 marks;; 4.2 x –2 (scale read from the wrong direction) 10 = 1 mark OR 2.5 x –3 (scale read as 3.7 mm not 3.7 cm) 10 = 1 mark OR 2.4 x –2 (scale read as 36.5) = 1 mark 10 OR Correct answer not in standard form and/or not to 2 significant figures, eg 0.0247/0.025/2.47 x 10 –2 = 1 mark OR Answer in incorrect standard form eg 25 x 10 –3 or 0.25 x 10 –1 = 1 mark OR Evidence of 37 ÷ 1500 or 37 ÷ (25 x 60) = 1 mark 2 02.2 (2 x AO2) 6 MARK SCHEME – A-LEVEL BIOLOGY – 7402/3 – JUNE 2023 Question Marking Guidance Mark Comments 02.3 1. Maltose is a disaccharide; 2. (Time to be) hydrolysed into glucose OR (Time to) break glycosidic bond(s); 2 (2 x AO2) 1. Accept maltose is made of two glucose/ monosaccharides 2. Accept monosaccharides for glucose Question Marking Guidance Mark Comments 02.4 This method would be less accurate because 1. Colour/endpoint is subjective; 1. Accept descriptions of the The accuracy of this method could be improved word ‘subjective’ by 2. Accept use a 2. (Have a) colour standard (of the yellow) as a colorimeter to time reference for the end point; 2 how long it takes (2 x to reach a certain OR AO3) value/absorbance/ (Have a) colorimeter/absorbance/transmission transmission 2. Ignore any reading (of the yellow) as a reference for the references to end point; coloured filters used in a colorimeter 7 MARK SCHEME – A-LEVEL BIOLOGY – 7402/3 – JUNE 2023 Question Marking Guidance Mark Comments 03.3 30; Accept correct number of generations from incorrect response to 03.2, Table 1 on page 11 will help with this Examples of how to use logs to solve 2 x 8 = 9.14 x 10 1 ln(2 x = ln(9.14 x 10 8 ) ) x . ln(2) = ln(9.14 x (AO2) 8 10 ) x = ln (9.14 ×10 8 ) ln (2) x = 30 OR 2x = 9.144 x 108 log2 (9.144 x 10 8 = ) 29.768 (so 30 generations) 10 MARK SCHEME – A-LEVEL BIOLOGY – 7402/3 – JUNE 2023 Table 1 for question 03.3 11 Number of Standard Population generations form size 1 2 x 100 2 2 4 x 100 4 3 8 x 100 8 4 1.6 x 101 16 5 3.2 x 101 32 6 6.4 x 101 64 7 1.28 x 102 126 8 2.56 x 102 256 9 5.12 x 102 512 10 1.024 x 103 1024 11 2.048 x 103 2048 12 4.096 x 103 4096 13 8.192 x 103 8192 14 1.638 x 104 16384 15 3.277 x 104 32768 16 6.553 x 104 65536 17 1.311 x 105 131072 18 2.621 x 105 262144 19 5.243 x 105 524288 20 1.049 x 106 1048576 21 2.097 x 106 2097152 22 4.194 x 106 4194304 23 8.388 x 106 8388608 Number of Standard Population generations form size 24 1.678 x 107 16777216 25 3.355 x 107 33554432 26 6.711 x 107 67108864 27 1.342 x 108 134217728 28 2.684 x 108 268435456 29 5.369 x 108 536870912 30 1.073 x 109 1073741824 31 2.147 x 109 2147483648 32 4.295 x 109 4294967296 33 8.590 x 109 8589934592 34 1.718 x 1010 17179869184 35 3.436 x 1010 34359738368 36 6.872 x 1010 68719476736 37 1.374 x 1011 38 2.749 x 1011 39 5.498 x 1011 40 1.100 x 1012 41 2.199 x 1012 42 4.398 x 1012 43 8.796 x 1012 44 1.759 x 1013 45 3.518 x 1013 MARK SCHEME – A-LEVEL BIOLOGY – 7402/3 – JUNE 2023 Question Marking Guidance Mark Comments 03.4 1. The concentration (of chloramphenicol) was too Accept as an low/dilute (to kill all) additional mark point 4. Chloramphenicol/ OR antibiotic not (evenly) mixed in There were too many M. luteus/bacteria for the liquid chloramphenicol/antibiotic to kill; 2 max culture/bottle (2 x 2. (Contamination with) other/resistant bacteria; AO3) 3. Mutation (occurred); 12 MARK SCHEME – A-LEVEL BIOLOGY – 7402/3 – JUNE 2023 Question Marking Guidance Mark Comments 04.3 A correct answer 34% = 2 marks;; 2 Evidence of 2 and 1 = 1 mark (2 x An answer of 42.8/43% = 1 mark (answer that did AO2) not subtract the ‘control’ from read values) Question Marking Guidance Mark Comments 04.4 Connexin-43 1. (Connexin-43) allows impulses to pass to the 1. Accept (connexin- bottom/apex of the heart/ventricles 43) allows diffusion/movement OR of ions (between cardiomyocytes) (Connexin-43) allows impulses to pass through 1. Ignore references Purkyne tissue/the bundle of His; to signals/ information/ GATA-4 2 messages 2. More actinomyosin bridges (2 x AO3) 2. Accept cross OR bridges for actinomyosin More binding sites on actin bridges 2. Accept more OR binding of myosin to actin More myosin filaments/heads; 15 MARK SCHEME – A-LEVEL BIOLOGY – 7402/3 – JUNE 2023 Question Marking Guidance Mark Comments 05.1 1982 and 2003; 1 (AO3) Reject if any other years are given Question Marking Guidance Mark Comments 05.2 1. There were many/48 (different) species OR (1997 had) the highest number of (different) species; 2. (However,) one/a few species were present in (very) large numbers OR Most species were present in (very) small numbers; 2 (2 x AO2) 1. Accept a lot/lots of (different) species for many 2. Accept dominated by one/a few species 2. Ignore each/all species were present in (very) small numbers 16 MARK SCHEME – A-LEVEL BIOLOGY – 7402/3 – JUNE 2023 Question Marking Guidance Mark Comments 05.3 1. The species richness/d are lower after 29 years; 2. The data is only for one (fish/local) community/site OR The data might not be representative of all fish communities OR Other communities might have different (fish) species; 3. (The measurements) only done in October OR The community might be different at other times of year (other than October); 4. The volume/temperature of the heated water (released each year) might have varied OR Timing/frequency of heated water release (each year) not known; 5. Fluctuations suggest other named factor had an effect (on biodiversity/species richness/d); 6. Species richness/d are not the only measures of ‘effect’; 7. Don’t know when the power station opened OR There is no data before 1980 OR There is no data before heated water was released OR No control (river) to compare with; 4 max (4 x AO3) 5. Named factors could include weather/oxygen concentration/food availability/plants/ predators/prey/ insects/ invertebrates/ fishing 17 MARK SCHEME – A-LEVEL BIOLOGY – 7402/3 – JUNE 2023 Question Marking Guidance Mark Comments 06.4 Cellular response 1. Female to female no significant difference in cellular response as SD overlap; 2. Male to male no significant difference in cellular response as SD overlap; 3. Significant increase in cellular response in autoimmune male compared with autoimmune female as SD do not overlap Humoral response 4. Male to male no significant difference in humoral response as SD overlap; 5. Female to female significant increase in humoral response as SD do not overlap; 6. Significant increase in humoral response in autoimmune female compared with autoimmune male as SD do not overlap 3 max (3 x AO3) Max 2 for answers only relating to the cellular response or humoral response Accept ‘(ear) thickness’ for cellular response, and ‘concentration of anti-OXA/antibody’ for humoral response If no other marks awarded, accept 1 principle mark for the idea that if SD overlap there is no significant difference or the converse 1. 2. and 4. Accept difference (likely) due to chance for no significant effect 3. 5. and 6. Accept increase not (likely) due to chance for significant increase Allow ‘error bars’ for ‘SD’ 20 MARK SCHEME – A-LEVEL BIOLOGY – 7402/3 – JUNE 2023 Question Marking Guidance Mark Comments 06.5 Supporting 1. (Oestrogen) increases the humoral response that produces antibody; 2. More antibodies could increase progression of SLE; 3. (Oestrogen) decreases the cellular response that produces TC cells; 4. Fewer TC cells could decrease/slow progression of RA; 5. Mice and humans are both mammals, so likely to have similar effects in both; Against 6. Increase in response might mean quicker production of antibody (not more) OR Decease in response might mean slower production of TC cells (not fewer); 7. Decrease in cellular response could (also) mean fewer antigen-presenting cells (and not just TC cells); 8. (Investigation) done in mice/not humans; 9. Table 3 does not state which type of autoimmune disease the mice had OR Mice might not suffer from SLE/RA; 4 max (4 x AO3) Max 3 for reasons supporting or against 21 MARK SCHEME – A-LEVEL BIOLOGY – 7402/3 – JUNE 2023 Question Marking Guidance Mark Comments 06.6 No – no mark Award as mark points 1. Mice with autoimmune disease will be unlikely 1 and 2, OR 3 and 4 to reproduce/survive OR Mice with autoimmune disease will be selected against; 2. Will not pass on allele (for autoimmune 2 max disease) (2 x OR AO2) Allele frequency (for autoimmune disease) will reduce/change; Yes – no mark 3. As long as the autoimmune disease did not affect the mice’s ability to reproduce/survive; 4. The allele frequency will remain constant/not change; 22 MARK SCHEME – A-LEVEL BIOLOGY – 7402/3 – JUNE 2023 Commentary on terms and statements in the levels mark scheme The levels mark scheme for the essay contains a number of words and statements that are open to different interpretations. This commentary defines the meanings of these words and statements in the context of marking the essay. Many words and statements are used in the descriptions of more than one level of response. The definitions of these remain the same throughout. Levels mark scheme word/statement Definition Holistic Synoptic, drawing from different topics (usually sections of the specification). A fully integrated answer which makes clear All topics relate to the title and theme of the links between several different topics and the essay; for example, explaining the biological theme of the question. importance of a process. When considering, for example, the importance of a process, the explanation must be at A-level standard. ‘Several’ here is defined as at least four topic areas from the specification covered. This means some sentences, not just a word or two. It does not mean using many examples from one topic area. Biology is detailed and comprehensive A-level Detailed and comprehensive A-level content is content, uses appropriate terminology, and is the specification content. very well written and always clearly explained. Terminology is that used in the specification. Well written and clearly explained refers mainly to biological content and use of terminology. Prose, handwriting and spelling are secondary considerations. Phonetic spelling is accepted, unless examiners are instructed not to do so for particular words; for example, glucagon, glucose and glycogen. No significant errors or irrelevant material. A significant error is one which significantly detracts from the biological accuracy or correctness of a described example. This will usually involve more than one word. Irrelevant material is several lines (or more) that clearly fails to address the title, or the theme of the title. For top marks in the band, the answer shows An example that is relevant to the title and is not evidence of reading beyond specification required in the specification content. The requirements. example must be used at A-level standard. Response mostly deals with suitable topics but Not addressing the biological theme of the they are not interrelated and links are not made essay (eg importance) at A-level standard. to the theme of the question. 25 MARK SCHEME – A-LEVEL BIOLOGY – 7402/3 – JUNE 2023 Question Marking Guidance Mark 07.1 The importance of interactions between organisms and their environment. • 3.1.2 Carbohydrates (the relationship of structure to function of glycogen, starch and cellulose in animal cells and plant cells) • 3.1.4.2 Many proteins are enzymes (enzyme inhibitors) • 3.1.7 Water • 3.2.3 Transport across cell membranes • 3.2.4 Cell recognition and the immune system • 3.3.1 Surface area to volume ratio • 3.3.2 Gas exchange • 3.3.3 Digestion and absorption • 3.3.4.1 Mass transport in animals • 3.3.4.2 Mass transport in plants • 3.4.4 Genetic diversity and adaptation • 3.4.5 Species and taxonomy (courtship) • 3.4.6 Biodiversity within a community [25 marks] • 3.5.1 Photosynthesis (13 x AO1, • 3.5.3 Energy and ecosystems 12 x AO2) • 3.5.4 Nutrient cycles • 3.6.1.1 Survival and response • 3.6.1.2 Receptors • 3.6.1.3 Control of heart rate • 3.6.2.1 Nerve impulses • 3.6.2.2 Synaptic transmission (effects of drugs) • 3.6.4.1 Principles of homeostasis and negative feedback • 3.6.4.2 Control of blood glucose concentration • 3.6.4.3 Control of blood water potential • 3.7.1 Inheritance • 3.7.3 Evolution may lead to speciation • 3.7.4 Populations in ecosystems • 3.8.1 Alteration of the sequence of bases in DNA can alter the structure of proteins • 3.8.2.1 Most of a cell’s DNA is not translated • 3.8.2.2 Regulation of transcription and translation • 3.8.2.3 Gene expression and cancer In order to fully address the question and reach the highest mark bands students must also include at least four topics in their answer, to demonstrate a synoptic approach to the essay. Students may be able to show the relevance of other topics from the specification. Note, other topics from beyond the specification can be used, providing they relate to the title and contain factually correct material of at least an A-level standard. Credit should not be given for topics beyond the specification which are below A-level standard. 26 MARK SCHEME – A-LEVEL BIOLOGY – 7402/3 – JUNE 2023 Question Marking Guidance Mark 07.2 The importance of membranes in the functioning of cells. • 3.1.3 Lipids (phospholipids) • 3.2.1.1 Structure of eukaryotic cells • 3.2.1.2 Structure of prokaryotic cells • 3.2.2 All cells arise from other cells (nuclear membrane breakdown in mitosis) • 3.2.3 Transport across cell membranes • 3.2.4 Cell recognition and the immune system • 3.3.1 Surface area to volume ratio • 3.3.2 Gas exchange [25 marks] • 3.3.3 Digestion and absorption (13 x AO1, • 3.4.2 DNA and protein synthesis 12 x AO2) • 3.5.1 Photosynthesis • 3.5.2 Respiration • 3.6.1.2 Receptors • 3.6.2.1 Nerve impulses • 3.6.2.2 Synaptic transmission • 3.6.3 Skeletal muscles are stimulated to contract by nerves and act as effectors • 3.6.4.2 Control of blood glucose concentration • 3.6.4.3 Control of blood water potential • 3.8.2.2 Regulation of transcription and translation In order to fully address the question and reach the highest mark bands students must also include at least four topics in their answer, to demonstrate a synoptic approach to the essay. Students may be able to show the relevance of other topics from the specification. Note, other topics from beyond the specification can be used, providing they relate to the title and contain factually correct material of at least an A-level standard. Credit should not be given for topics beyond the specification which are below A-level standard. 27