AQA A Level Biology 2021 assessment materials - Biological Molecules / Cells

AQA A Level Biology 2021 assessment materials - Biological Molecules / Cells Describe the chemical reactions involved in the conversion of polymers to monomers and monomers to polymers Give TWO named examples of polymers and their associated monomers to illustrate your answer - Correct Answer 1. A condensation reaction joins monomers together and forms a (chemical) bond and releases water 2. A hydrolysis reaction breaks the (chemical) bond between monomers and uses water 3 and 4. 2 suitable examples of polymers and monomers from which they are made 5. Correct bond within a named polymer Amino Acids --> Polypeptide (peptide bond) Nucleotides --> DNA (phosphodiester bond Alpha Glucose --> Starch/Glycogen (glycosidic bond) Beta Glucose --> Cellulose (glycosidic bond) The action of the carrier protein X in figure 1 is linked to a membrane-bound ATP hydrolase enzyme. Explain the function of this ATP hydrolase. - Correct Answer Hydrolyses ATP to ADP and Pi (and energy released) 3D shape / tertiary structure of enzyme is changed to actively transport substance across the membrane The movement of Na+ OUT of the cell allows the absorption of glucose INTO the cell lining the ileum. Explain how. - Correct Answer Na+ ions pumped out (into blood) by sodium potassium pump = electro-chemical gradient - higher concentration Na+ in lumen compared to cells Na+ ions diffuse back into cell from lumen via co-transport protein, bringing glucose with it Describe and explain TWO features you would expect to find in a cell specialised for absorption - Correct Answer - microvilli / folding of c s membrane = larger SA FOR DIFFUSION - many carrier proteins for active transport Draw phospholipids on Figure 2 to show how the carrier protein, SGLT1, would fit into the cell-surface membrane - Correct Answer Describe how amino acids join to form a polypeptide so there is always NH2 at one end and COOH at the other end - Correct Answer COOH of one amino acid and NH2 of another amino acid react in a condensation reaction, creating a peptide bond between the two amino acids and releasing water !!!!!!! NOT MARK SCHEME ANSWER!!!!!! Formation of an enzyme-substrate complex increases the rate of reaction. Explain how. - Correct Answer - reduces activation energy - due to bending bonds OR without enzyme, very few substrates have sufficient energy for reaction A scientist measured the rate of removal of amino acids from a polypeptide with and without an enzyme present. With the enzyme present, 578 amino acids were released per second. Without the enzyme, 3.0 × 10^−9 amino acids were released per second. Calculate by how many times the rate of reaction is greater with the enzyme present. Give your answer in standard form. - Correct Answer 578/(3.0 * 10^-9) = 1.93 x 10^11 Calculate the rate of reaction of the enzyme activity with no lyxose at 2.5 mmol dm−3 of ATP as a percentage of the maximum rate shown with lyxose. - Correct Answer No lyxose at 2.5 mmol dm−3 = 0.44 Max rate with lyxose = 1.4 100 * 0.44/1.4 = 31.4% Lyxose binds to an enzyme (causing a higher rate of reaction. Suggest a reason for the difference in the results shown in Figure 5 with and without lyxose. - Correct Answer 1. binding alters enzyme 3D structure 2. active site changes shape 3. more (successful) ESCs form per minute / ESCs form more quickly / activation energy further decreased Alpha-gal is made of 2 galactose molecules. Galactose has formula C6H12O6 => Alpha-gal formula? - Correct Answer 2 * C6H12O6 = C12H24O12 - H2O = C12H22011 Describe how alpha-gal (a disaccharide) is formed from two galactose molecules - Correct Answer - condensation reaction between 2 galactose molecules - forming a glycosidic bond