MARK SCHEME – A-LEVEL BIOLOGY PAPER 2 – 74022 – SPECIMEN

MARK SCHEME A LEVEL BIOLOGY PAPER 2 74022 SPECIMEN Equilibrium reached; 2. Allow for expansion/pressure change in apparatus; 3. Allow respiration rate of seeds to stabilise; 3 1. Accept equilibrate 3. Ignore seeds acclimatise 01.2 1. Optimum temperature/temperature for normal growth of seeds; 2. (Optimum temperature) for enzymes involved in respiration; 2 01.3 1. Oxygen taken up/used by seeds; 2. CO2 given out is absorbed by KOH (solution); 3. Volume/pressure (in B) decreases . Calcium ions diffuse into myofibrils from (sarcoplasmic) reticulum; 2. (Calcium ions) cause movement of tropomyosin (on actin); 3. (This movement causes) exposure of the binding sites on the actin; 4. Myosin heads attach to binding sites on actin; 5. Hydrolysis of ATP (on myosin heads) causes myosin heads to bend; 6. (Bending) pulling actin molecules; 7. Attachment of a new ATP molecule to each myosin head causes myosin heads to detach (from actin sites); 5 max 02.2 1. Releases relatively small amount of energy / little energy lost as heat; 2. Releases energy instantaneously; 3. Phosphorylates other compounds, making them more reactive; 4. Can be rapidly re-synthesised; 5. Is not lost from/does not leave cells;