Biology paper (1)

• Cells of villi contain many mitochondria for active transport.
• Alveoli and villi both have a large surface area to maximise diffusion.
• Villi have a large surface area to maximise diffusion and thin walls or walls that are one cell thick to reduce diffusion distance or time.
• Villi have a good blood supply or a capillary network to maintain a concentration gradient.
• Alveoli and villi both have a good blood supply or a capillary network to maintain a concentration gradient.
• Villi are in close proximity to the blood supply to reduce diffusion distance or time.
• Alveoli and villi are in close proximity to the blood supply to reduce diffusion distance or time.
• Alveoli and villi both have thin walls or have walls that are one cell thick to reduce diffusion distance or time.
• Villi have microvilli to further increase surface area.
• Villi contain microvilli to further increase surface area.
• White blood cells or phagocytes identify monoclonal antibodies and engulf or destroy antibody-bound HIV.
• Antibodies destroy the active virus or HIV.
• Monoclonal antibody is used as a tool to identify HIV throughout.
• Monoclonal antibodies attach to all HIV antigens, preventing HIV from binding to a human cell or entering human cell genetic material.
• Correct or specific antibodies are produced quickly.
• Monoclonal antibody with anti-retroviral drug attached attaches to HIV antigens, destroying the virus or its genetic material.
• Monoclonal antibody is complementary or specific to HIV antigen.
• Inactive HIV virus is injected into the bloodstream, muscle, or body, causing white blood cells to produce antibodies against the inactive virus.
• The descriptor for the level indicates the different qualities that might be seen in the student’s answer for that level.
• If the answer covers different aspects of different levels of the mark scheme, a best fit approach can be used for defining the level.
• The mark scheme can be applied by determining a level and then deciding on the mark within that level.
• An answer which contains nothing of relevance to the question must be awarded no marks.
• Before you apply the mark scheme to a student’s answer, read through the answer and, if necessary, annotate it to show the qualities that are being looked for.
• Indicative content in the mark scheme is provided as a guide for examiners, it is not intended to be exhaustive and examiners must credit other valid points.
• The variability of the response can be used to help decide the mark within the level, for example, if the response is predominantly level 2 with a small amount of level 3 material, it would be placed in level 2 but be awarded a mark near the top of the level because of the level 3 content.
• Once a level has been assigned, the mark can be determined by comparing the student’s answer with an example answer which has been awarded a mark by the Lead Examiner.
• The descriptor for the level shows the average performance for the level.
• There are two marks in each level.
• Each new cell has the same set of DNA, alleles, or genes as the other.
• Guard cells are used in plant tissues.
• The set of chromosomes in each new cell are identical to one another.
• Transpiration moves substances upwards and translocation moves substances upwards and downwards.
• Transpiration involves xylem and translocation involves phloem.
• The replicated chromosomes are separated, allowing two new nuclei to form and allowing the nucleus to divide into two.
• Genetic material, DNA or chromosomes, is doubled, replicated, copied, or duplicated.
• Warm conditions with low humidity are not suitable for plants.
• Differentiation is different from specialisation.
• Transpiration transports water and minerals/ions and translocation transports dissolved sugars.
• The replicated chromosomes are pulled or moved apart.
• Transpiration does not require energy to move substances and translocation does require energy to move substances.