AQA A-Level Biology Paper 1: June 2019 - Practice Questions and Answers, Exams of Advanced Education

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biology paper 1 june 2019

aqa a level

describe how a non-competative inhibitor can reduce the rate of an enzyme-controlled reaction

• attaches to the enzyme at allosteric site
• changes shape of active site
• so active site and substrate no longer complementary so less enzyme-substrate complexes form the scientist concluded that pectin is a non-competative inhibitor of the lipase enzyme. how did the scientist conclude this?
• looking at the graph. with the inhibitor the increase lipid concentration doesn't increase the rate of reaction. explain how human mass at birth is affected by stabilizing selection
• most likely to be transferred to a special care unit are those under 2800g
• extreme mass babies least likely to survive and so less likely to pass on their alleles
• extreme mass at birth decreases in frequency in the population what is the structure of HIV?
• viral RNA
• reverse transcriptase
• capsid
• phospholipid viral envelope
• attachment proteins why do HIV controllers not develop symptoms of AIDS?
• have more T helper cells
• lower viral load to destroy helper T cells
• so more activation of B cells
• with B cells more, production of plasma cells ability to kill virus infected cells
• more able to destroy other microbes describe how BrdU would be incorporated into new DNA during semi-conservative replication
• DNA helicase breaks hydrogen bonds between 2 DNA strands
• BrdU complementary to adenine on template strand
• DNA polymerase joins adjacent nucleotides to incorporate BrdU into the new DNA strand
• phosphodiester bonds form between nucleotides Explain five properties that make water important for organisms.

• metabolite in condensation
• solvent so metabolic reactions can occur
• high heat capacity so buffers changes in temperature
• large latent heat of vaporisation so provides a cooling effect through evaporation
• cohesion between water molecules so supports columns of water in plants and produces surface tension supporting small organisms Describe the biochemical tests you would use to confirm the presence of lipid, non-reducing sugar and amylase in a sample. lipid:

1. add ethanol then add water and mix
2. milky white emulsion means lipids present non-reducing sugar:
3. do benedict's test and stays blue
4. boil with acid then neutralise with alkali
5. heat with benedict's and forms red/orange ppt amylase:
6. add biuret reagent and becomes purple
7. add starch (leave for time), test for reducing sugar