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. S