2024 AQA AS BIOLOGY 7401/1 Paper 1 Question Paper & Mark scheme (Merged) June 2023 VERIFIED / Biology AQA AS level 7401/1 Paper 1

2024 AQA AS BIOLOGY 7401/1 Paper 1 Question Paper & Mark scheme (Merged) June 2023 VERIFIED / Biology AQA AS level 7401/1 Paper 1 Describe the induced-fit model of enzyme action - ANSWER-- active site not complementary to/does not fit substrate - Shape of active site changes as enzyme- substrate complex forms - Distorting bonds (in substrate leading to reaction) • The human cell then makes a complementary strand to the HIV DNA. The complementary strand is made in the same way as a new complementary strand is made during semi-conservative replication of human DNA. Describe how the complementary strand of HIV DNA is made. - ANSWER-- there are complementary nucleotides/bases pair - DNA polymerase used - Nucleotides join together (to form new strand)/phosphodiester bonds form; Contrast the structures of DNA and mRNA molecules to give three differences. - ANSWER-- DNA is double stranded/double helix and mRNA single-stranded; - DNA (very) long and RNA short; -Thymine/T in DNA and uracil/U in RNA; - Deoxyribose in DNA and ribose in RNA; Describe the difference between the structure of a triglyceride molecule and the - ANSWER-In phospholipid, one fatty acid replaced by a phosphate Describe how you would test for the presence of a lipid in a sample of food - ANSWER-- Add ethanol, then add water; -White (emulsion shows lipid) Describe how a saturated fatty acid is different from an unsaturated fatty acid - ANSWER-Unsaturated has (at least one) double bond (between carbons) This fat substitute cannot be digested in the gut by lipase. Suggest why. - ANSWER-- (Fat substitute) is a different/wrong shape/not complementary - Unable to fit/bind to (active site of) lipase/no ES complex formed; Despite being a lipid, the substitute cannot cross the cell-surface membranes of cells lining the gut. Suggest why it cannot cross cell-surface membranes. - ANSWER-It is hydrophilic/is polar/is too large/is too big; Cells constantly hydrolyse ATP to provide energy. Describe how ATP is resynthesised in cells. - ANSWER-- From ADP and phosphate; - By ATP synthase; - During respiration/photosynthesis; Give two ways in which the hydrolysis of ATP is used in cells. - ANSWER-- To provide energy for other reactions/named process; - To add phosphate to other substances and make them more reactive/change their shape What is the evidence from Figure 2 that a scanning electron microscope was used to take this photograph? - ANSWER-(Can see) 3D image name the part of the mitochondrion labelled X in Figure 2 - ANSWER-Crista/cristae Y is a protein. One function of Y is to transport cellulose molecules across the phospholipid bilayer. Using information from Figure 3, describe the other function of Y. - ANSWER-- (Y is) an enzyme/has active site/forms ES complex; - That makes cellulose In the cell wall, bonds hold the cellulose molecules together side by side. Name that bond - ANSWER-Hydrogen Name the products of the hydrolysis of sucrose. - ANSWER-glucose and fructose Describe how giving this vaccine leads to production of antibody against HPV - ANSWER-- Vaccine contains HPV