BIOLOGY AQA AS LEVEL7401 1 PAPER 1 EXAM, Exams of Advanced Education

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BIOLOGY AQA AS LEVEL7401 1 PAPER 1

EXAM

• 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. - -- 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. - -- 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 - -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 - -- Add ethanol, then add water; -White (emulsion shows lipid) Describe how a saturated fatty acid is different from an unsaturated fatty acid - -Unsaturated has (at least one) double bond (between carbons)

This fat substitute cannot be digested in the gut by lipase. Suggest why. - -- (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. - -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. - -- From ADP and phosphate;
• By ATP synthase;
• During respiration/photosynthesis; Give two ways in which the hydrolysis of ATP is used in cells. - -- 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? - -(Can see) 3D image name the part of the mitochondrion labelled X in Figure 2 - -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. - -- (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 - -Hydrogen Name the products of the hydrolysis of sucrose. - -glucose and fructose Describe the induced-fit model of enzyme action - -- 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) Describe how giving this vaccine leads to production of antibody against HPV - -- Vaccine contains HPV antigen
• Displayed on antigen-presenting cells
• Specific helper T cell (detects antigen and) stimulates specific B cell
• B cell divides to give plasma cells
• B cell/plasma cell produces antibody Give two ways doctors could use base sequences to compare different types of HPV. - -- Compare (base sequences of) DNA
• Look for mutations (that change the base sequence)
  • Compare (base sequences of) (m)RNA Chromosomes line up on the equator of the mitotic spindle in the... - - Metaphase Suggest why the development of a monopolar mitotic spindle would prevent successful mitosis - -- No separation of chromosomes

• chromosomes all go to one pole of cell
• one daughter cell gets no chromosomes or chromatids; Describe what happens in the hydrolysis - -- Peptide bond broken
• Using water Many people with Alzheimer's disease have mutations that decrease α- secretase production or increase β-secretase production (lines 8-9). Use the information provided to explain how these mutations can lead to Alzheimer's disease. - -- Mutations prevent production of enzyme
• (Increase in β-secretase) leads to more β-amyloid production
• (Leads to) more/greater plaque formation One possible type of drug for treating Alzheimer's disease is a competitive inhibitor of β-secretase (lines 10-11). Explain how this type of drug could prevent Alzheimer's disease becoming worse. - -- (Inhibitor) binds to active site of β-secretase
• reduces production of β- amyloid/plaque When some of these types of drugs were trialled on patients, the trials were stopped because some patients developed serious side effects (lines 11-13). Using the information provided, suggest why some patients developed serious side effects. - -- Some β-amyloid required/needed (to prevent side effects)
• Leads to build-up of amyloid-precursor protein (that causes harm) OR Too much product of α-secretase (causes harm)

Figure 1 shows the co-transport mechanism for the absorption of amino acids into the blood by a cell lining the ileum.The addition of a respiratory inhibitor stops the absorption of amino acids. Explain why. - -- No active transport

• Sodium (ions) not moved (into/out of cell)
• No concentration gradient for sodium (to move into cell with amino acid)