OCR A_Level Biology Paper 1 Marking Scheme.

OCR A_Level Biology Paper 1 Marking Scheme. Question Answer Marks AO element 1 D 1 1.2 2 B 1 1.1 3 A 1 1.1 4 A 1 1.1 5 B 1 1.1 6 B 1 1.1 7 B 1 1.1 8 B 1 1.1 9 A 1 2.6 10 A 1 2.6 11 C 1 2.3 12 C 1 2.4 13 B 1 1.1 14 C 1 1.2 15 B 1 2.5 Total 15 H420/01 Mark Scheme Question Answer Marks AO element 16 (a) (i) adenine 1 2.1 DO NOT ALLOW adenosine IGNORE nitrogenous base / purine (a) (ii) hydrolysis 1 2.1 IGNORE dephosphorylation (a) (iii) because ATP is , broken down / hydrolysed (to ADP) ATP is constantly recycled ATP used to provide energy for , (named) metabolic reactions / processes ATP is , not stored long term / used immediately max 2 2.1 ALLOW ATP is unstable ALLOW constant interconversion of ATP and ADP (+Pi) ALLOW ATP produced is coupled to metabolic reactions IGNORE used for respiration unqualified ALLOW ATP is used as fast as it is produced H420/01 Mark Scheme Question Answer Marks AO element 16 (b) (i) Substance A 1 for (substance) A the , graph is a straight line / rate of uptake depends on concentration 4 max 3.1 3.2 ALLOW rate is (directly) proportional to concentration ALLOW as concentration increases rate increases 2 (so substance) A is (absorbed by simple) diffusion DO NOT ALLOW facilitated diffusion Substance B 3 for (substance) B the curve , reaches a plateau / levels off ALLOW rate becomes constant DO NOT ALLOW rate slows IGNORE stops increasing 4 (so substance) B could be (absorbed by) , facilitated diffusion / active transport 5 (because) if facilitated diffusion channels / carrier proteins , become saturated OR (because) if active transport carrier proteins / carriers , become saturated ALLOW channels / carriers working at maximum capacity ALLOW transport proteins for either in MP5 DO NOT ALLOW channel proteins for active transport H420/01 Mark Scheme 16 (b) (ii) Substance A effect (uptake) unaffected / no change max 4 3.1 2.5 CHECK answer to (b)(i) ALLOW ECF if answer to part (i) suggests candidate thinks substance A is taken up by active transport and Substance B is taken up entirely by diffusion. explanation (simple) diffusion , does not require ATP / is a passive process ALLOW does not require energy Substance B effect if active transport slower / little / reduced / no (uptake) explanation active transport , requires ATP / is an active process OR effect if facilitated diffusion (uptake) unaffected / no change explanation facilitated diffusion , does not require ATP / is a passive process ALLOW does not require energy H420/01 Mark Scheme Question Answer Marks AO element 16 (c) 4 2.3 One mark per correct line DO NOT ALLOW more than one line per box Improvement Justification To assess repeatability Use a colorimeter with a digital display showing absorbance units to 3 decimal places. To assess reproducibility Check the zero value of the colorimeter with purified water before use. To reduce systematic error For each concentration, repeat the measurement of the rate of reaction three times and calculate a mean. To reduce random error (uncertainty) Ask students in several schools to carry out the same investigation. To increase resolution