Paper 1

• Describe how mineral ions are taken up by root hair cells (3)

  • (Mineral ions) are taken up by active transport (1) 
  • Through carrier proteins (1)
  • This requires {energy / ATP} (1)
• Explain why a diet based on plant protein produces lower greenhouse gas emissions than a diet based on animal protein (3)

  • Because plants produce {organic compounds/biomass} from photosynthesis (1)
  • Plants remove carbon dioxide(from the atmosphere) (1)
  • Because animals produce(more) carbon dioxide by respiration (1)
  • Because (some) animals produce methane (1)
• Nitrate ions are required for the synthesis of...

  • Amino acids
• Phosphate ions are required for the synthesis of...

  • Nucleic acids
• Magnesium ions are present in the structure of...

  
  

  • Chlorophyll
• Explain why the farming of beef cattle on deforested land produces more greenhouse gas emissions than from those reared on natural pastures (3)

  • (deforestation cuts down) trees which are carbon sinks (1)
  • {burning / decomposition} of these trees releases carbon dioxide into the atmosphere (1)
  • Without trees there is {less/no} photosynthesis to remove carbon dioxide (from the atmosphere) (1)
• State how the age of the layers in a peat bog can be determined (1)

  • Using carbon (14) dating
• Explain why the conditions in peat bogs prevent decomposition (3)

  
  

  Conditions are anaerobic (1)

  Therefore less (aerobic) respiration by decomposers (1)

  Acidic conditions {inhibit /denature} enzymes (1)

  Therefore (enzymes) cannot {digest / break down} organic material (1)
• Devise a procedure to measure the rate of recovery of the peat bog (4)

  Use of quadrats for sampling (1)

  Method of determining co-ordinates for random sampling (1)

  Record percentage cover of sphagnum (in each quadrat) (1)

  Several {quadrats/samples} measured and mean calculated (1)

  Sample at regular time intervals (1)

  Calculate the rate of change in sphagnum cover (1)
• The GM fungus transcribes and translates the gene for this protein. Describe the primary structure of a protein (2)

  
  

  • Sequence of amino acids (1)
  • Joined together by peptide bonds (1)
• Explain why this mutation may prevent the enzyme involved in the production of haem from functioning correctly (4)

  • A mutation will lead to a change in the sequence of bases (in the DNA) (1)
  • (therefore a mutation) may lead to {a different amino acid/change in the sequence of amino acids} (1)
  • So different R groups would change the tertiary structure of the enzyme (1)
  • Therefore the (shape of the) active site is changed (1)
  • Therefore substrate does not fit active site of enzyme/substrate-enzyme complexes cannot form (1)
• Draw and label a mitochondrion (2)

  Labelled inter-membrane space, cristae, matrix, inner membrane, outer membrane
• Explain why a fertilised egg cell will contain only maternal mitochondria

  • Only the nucleus of the sperm enters the ovum (1)
  • (therefore) all the mitochondria come from the egg cell (1)
• Antibodies are released into the blood when...

  • B cells are activated to become plasma cells
• Describe passive artificial immunity...

  • People can be given an injection / transfusion of antibodies e.g. the tetanus antitoxin
  • The antibodies will have been collected from people or animals whose immune system had been triggered by a vaccination to produce antibodies
• Describe passive natural immunity...

  • Foetuses receive antibodies across the placenta from their mothers
  • Babies receive antibodies in breast milk
• Describe active artificial immunity...

  • Acquired through vaccination
• Describe active natural immunity...

  • Acquired through exposure to pathogens
• Explain why, following a measles infection, it may be advisable for children to repeat other vaccinations they have had (3)

  • Due to a loss of memory cells there is no secondary immune response (1)
  • Therefore antibodies cannot be produced quickly (1)
  • Therefore there is less immunity (to diseases previously vaccinated against) (1)
  • Need to repeat vaccinations to produce more memory cells (1)
• The initial response when bacteria enter the body is a...

  • Non-specific response, bacteria are destroyed by phagocytes (1)
• M. tuberculosis bacteria can remain dormant in the body after infection. Explain why these dormant bacteria are not destroyed by the immune system (3)

  • The bacteria are inside {macrophages /phagocytes} (1)
  • This bacterium has a (thick) waxy cell wall (1)
  • Lysosomes cannot fuse with phagocytic vacuole / bacteria not destroyed by enzymes (1)
  • Bacteria within tubercles (cannot be destroyed) (1)
• Biodiversity can be measured by the number of...

  • The number of different species in a habitat
• Devise an investigation to compare the rate of the light-dependent reaction in shade tolerant and shade intolerant plants grown at different light intensities (6) Part 1

  • Use shade tolerant and shade intolerant plants
  • Plants grown in the same conditions e.g. temperature, humidity
  • Plants grown in either 5% light or 25% light or a range of light intensities
  • Take same masses of leaf
  • Add to equal volume of isolation medium
  • Homogenise (e.g. blend / grind in pestle and mortar) for same length of time
• Devise an investigation to compare the rate of the light-dependent reaction in shade tolerant and shade intolerant plants grown at different light intensities (6) Part 2

  • Filter suspensions of plant material (through muslin) or centrifuge to concentrate chloroplasts
  • Resuspend pellet of chloroplasts if centrifuged
  • Expose suspensions to 5% and 25% light intensity
  • Keep temperature controlled
  • Add DCPIP and record time for DCPIP to decolourise
  • Carry out repeats to calculate mean time to decolourise the DCPIP
• Describe the acrosome reaction?

  • The sperm cell releases enzymes that digest the zona pellucida
• state genetic diversity (1)

  • Number of different alleles in a species
• What is the definition of Endemic

  • Species found in only one geographical location
• How do you measure genetic diversity

  • Heterozygosity Index
• Genetic mutation

  • Genetic mutation results in variation in the population (1)
  • Selection pressure favours individuals with the advantageous allele (1)
  • Individuals with the advantageous allele survive, reproduce and pass on the advantageous allele to the offspring (1)
  • Increasing allele frequency over time (1)
• Molecular Phylogeny

  • Changes in sequence of amino acid reveal evolutionary/genetic relationship between organisms
  • The more closely related they are, the more similarities they will have
• Cystic Fibrosis

  • Many alveoli have a large surface area (1); alveoli covered with a rich network of capillaries
  • Steep concentration gradient- breathing/ventilation (1) and blood flow (1)
  • Short diffusion distance- walls of alveoli and capillaries are one cell thick (1) squamous epithelial cells of alveoli are flat (1)
• Describe the process of CFTR mutation

  • CFTR is a channel protein, responsible for the transport of chloride ions (Cl-) across the apical membrane, out of the cell and into the mucus, down the concentration gradient (through facilitated diffusion)
  • Water then moves across the apical membrane out of the cell and into the mucus, from a high concentration of free water molecules to low concentration (through osmosis) or from an area of low concentration of chloride ions (solute) to higher chloride concentration
  • This keeps the mucus hydrated; it can be removed by the cilia
• What is the immediate product of the light-independent reactions of photosynthesis?

  • GP
• What is the name of the enzyme used by plants to fix carbon dioxide?

  • RUBISCO
• Explain how changes in fibrinogen concentration might be a risk factor for CVD

  • Increased concentrations of fibrinogen leading to increased fibrin
  • Increase the risk of blood clotting / more frequent and extensive clotting
  • Blocking lumen of {arteries / capillaries}
• Explain how the blood-gas barrier of the chicken is adapted to give more efficient gas exchange than the blood-gas barrier of the dog (4)

  • Thinner blood-gas barrier
  • Because of thinner {alveolar walls / capillary walls / extracellular matrix layer}
  • Therefore a reduced diffusion distance
  • A faster rate of { diffusion / gas exchange }
• State what is meant by the term allele (1)

  • (Alternative form / different form / version / variation) of a gene
• State what is meant by the term sex-linkage (2)

  
  

  • {allele/gene} responsible for a trait is located on a sex chromosome
  • Expression of the trait is related to gender / one gender inherits only one allele for a trait
• Describe the structure of collagen (4)

  • Primary structure described as a repeating amino acid sequence
  • Three polypeptide chains
  • Cross-linking between the chains
  • Chains coiled around each other
• In which part of the chloroplast do the light-independent reactions take place?

  • Stroma