2023 A level paper 1

• give three structural features found in all viruses and describe the function of one of these features

  1. attachment proteins
  2. capsid
  3. DNA or RNA

  attachment proteins help to bind to receptors
• Explain why viruses are described as acellular and non-living

  they are described as acellular as they cannot replicate independently and are not made from cells.
• Give one reason why antibiotics are not effective against viruses

  antibiotics aren't effective against viruses as they have no cell wall
• Use Figure 1 to describe three ways the structure of chitin is similar to the structure of cellulose.

  chitin is similar to cellulose as they both are bonded by glycosidic bonds, form unbranched chains and have 1-4 bonds
• Explain the importance of one adaptation of the gas exchange surface in the tracheal system of an insect.

  tracheole cell wall is one cell think so they are able to allow for rapid diffusion
• Explain the importance of the xylem being kept open as a continuous tube. 


  xylem must be kept open as a continuous tube to allow for the flow of water. they also should be kept open for cohesion from hydrogen between all water molecules. they also should be kept open to allow for transpiration which creates tension.
• Other than the Golgi apparatus, name one structure in Figure 2 which shows that P. vivax is a eukaryote.

  rough endoplasmic reticulum
• Describe two functions of the Golgi apparatus in a eukaryotic cell.

  golgi apparatus helps to package lipids and proteins

  golgi apparatus helps to form golgi vesicles
• What does Figure 3 suggest is the order of human migration out of Africa?

  india, europe, east asia, central america, south america
• There are an estimated 229 million cases of human malaria worldwide per year. 94% of these cases are found in Africa, but are not caused by P. vivax. P. vivax does cause 61% of the cases of human malaria outside Africa. Use this information to calculate the number of cases worldwide caused by P. vivax each year.

  229000000 x 6% = 13740000

  13740000 x 61% = 8381400

  answer is 8381400
• In Africa today, most of the human population are resistant to malaria caused by P. vivax. Use your knowledge of natural selection to explain why this resistance is so common in Africa.

  this resistance is so common in africa as the mutation produces alleles so those with these alleles tend not to get malaria. these people survive and reproduce to pass the allele on and therefore this causes a higher proportion of alleles.
• Explain why the damage to the cells lining the ileum reduces absorption of the products of digestion and why this reduces absorption of water.

  this reduces absorption as microvilli is damaged so surface area is reduced which decreases the water potential in the ileum. the decrease in water potential causes water to move into ileum via osmosis.
• Use Figure 4 to suggest how this passive immunity would work and which patients should be offered this anti-toxin antibody.


  passive immunity would work by antitoxins causing phagocytosis of the toxin which prevents the chance of diarrhoea. so the patients with c difficile and diarrhoea should be offered the antibody.
• Describe how the anti-toxin antibody would be digested.

  they would be digested via proteases. the peptide bonds are hydrolysed by endopeptidases and exopeptidases. endopeptidases break bonds internally while exopeptidases break bonds externally
• Describe the aseptic techniques she should use.

  the aseptic techniques she should use is disinfecting all surfaces with a disinfectant, sterilising the pipette that'll be used for transfer and lift the agar plate lid at an angle.
• On each agar plate, the student cut a well (a hole) in the agar. The well had a diameter of 6 mm. The student added 50 mm3 of cinnamon oil into the well. Calculate the minimum depth of the well to allow the addition of 50 mm3 of cinnamon oil. Use the following equation in your calculation: Volume of a cylinder = πr 2 × l Use 3.14 as the value for π. Show your working.

  3.14 x 3^2 = 28.2743

  50 divided by 28.2743 = 1.768

  rounded = 1.77
• Suggest exactly what the student added to the wells to get the positive control and negative control results

  for the positive control she added disinfectant and for the negative control she added oil without cinnamon.
• Define genome and proteome

  genome = all of the alleles in a organism

  proteome = all of the proteins that cell can produce.
• Consider the accuracy and limitations of the early classification of bacteria using the arrangement of flagella.

  flagella can be difficult to stain so sometimes it may not be visible and not all bacteria have flagella. optical microscopes have a low resolution so your not able to distinguish between 2 structures very well.
• Suggest why several bacterial species have been renamed in recent years.

  updated microscopes such as electron microscopes allowing for higher resolution to see clearly.
• Using Figure 7, what can you conclude about how exposure to CO affects the loading and unloading of oxygen by haemoglobin? Explain your answer.

  exposure to co means less oxygen is loaded at a high partial pressure of oxygen. low partial pressure of oxygen means haemoglobin has higher affinity for oxygen therefore, haemoglobin unloads less at less partial pressure of oxygen.
• The cells in drawing A can be identified as those treated with MiTMAB. Explain why.

  there are 2 nuclei in the cells suggesting cytokinesis did not take place and was prevented.
• MiTMAB acts as a non-competitive inhibitor of an enzyme called dynamin. Suggest how MiTMAB can cause dynamin to become inactive.

  MiTMAB binds to dynamine at inhibitor site which changes the shape of the dynamin active site so no enzyme substrate complexes can from due to it ot being complementary.
• 8.3 Use all the information given to explain the results shown in Figure 9

  at lower concentrations of MiTMAB doesn't cause cell death so as the concentration increases cell death also increases meaning higher concentrations of MiTMAB causes cell death.
• Suggest what is on the test at line T and explain what causes the line to appear in a positive test.


  at the t line the enzymes are present and binds to the substrate to produce a colour change which is the line.
• A line at C shows that the test has worked. Suggest one reason why a line at C shows the test has worked

  it shows that the blood has moved up above the t line on the test
• Suggest why the fused cells allow continuous production of monoclonal antibodies.

  fused cells allow continuous production as they rapidly divide causing the b cells to produce the monoclonal antibodies.
• Evaluate the ethics of the production process shown in Figure 12

  they're abusing the rabbits life but are producing life changing medicine from it
• The scientists recommend that the new test is used for the identification of dengue fever in all countries around the world. Discuss this recommendation. Use all the information given


  the new test should be used as it performs better than the current one and detects earlier but not as early as the lab based test can. however, the new test is better than the lab based test from 5 days and onwards. this means that the lab based and new test are better than the current one and should be used.
• The dengue virus causes damage to capillaries so that blood proteins move out of the capillaries into the tissue fluid. Explain how this would affect the return of tissue fluid into the capillaries.

  this would cause the water potential to be lowered meaning less water will return via osmosis.
• Describe how a quaternary protein is formed from its monomers. Do not include the process of translation in your answer.

  the monomers of a quaternary protein are amino acids

  amino acids are bonded together via a condensation reaction to form peptide bonds between amino acids. the secondary structure is the amino acid sequence further processed to form alpha helixes or beta pleated sheets by hydrogen bonding. in the tertiary structure, hydrogen and ionic bonds form as well as disulfide bridges to create a unique 3d shape. the quaternary structure consists of more than 1 poly peptide.
• Describe the structure of DNA and the structure of a chromosome

  DNA is a polymer of nucleotides. nucleotides contain a deoxyribose sugar, phosphate and a nitrogenous base. these are bonded together via a condensation reaction to form phosphodiester bonds. the bases then bond together via hydrogen bonds to form a helical structure. complementary base pairing occurs where adenine bonds to thymine and cytosine bonds to guanine. the structure of a chromosome is two chromatids joined together via a centromere.
• Mutation can result in an increase in genetic variation within a species. Describe and explain the other processes that result in increases in genetic variation within a species.

  other processes which can result in genetic variation is the crossing over of homologous chromosomes via meiosis. they can also produce new combinations of alleles.