(Original post by Math12345)
AQA GCSE Biology Unit 2 Unofficial Markscheme
a. As you decrease the temperature the time taken to get the frostbite decreases (or you get frostbite more quickly). (1)
b. 9 or 10 minutes. (1) This was confusing, because it could be anywhere between 9 and 10.
c. Shivering and constriction. (2)
a. Control variables: mass of crushed apple / amount of drops of liquid. (1) There are more possibilities.
b. The drops can be different sizes. (1)
c. Amylase does not break down the cell wall like water. Pectinase enzyme digests the cell wall. Energy in boiling water causes the cell wall to break apart. (3) Improvement?
i. 11.6 cm^3 (1) Not sure...
ii. Pectinase enzyme is denatured at high temperatures, but boiling the apple still has the same effect. (2) Improvement?
a. Drug B - Kills pancreatic cells which means even less insulin is produced than before (which is why it only has negative effect on some diabetics). (2) Improvement?
b) Careful attention to diet and pancreatic cell transplants (2) There are more possibilities.
c) The insulin enzymes are destroyed by the digestive system or The insulin in the tablet would not reach the blood (1) I am sure there are many other possible things you could have write
a. Cloudy means less light so less photosynthesis so less CO2 used. (2) Improvement?
b. Magnesium. (1)
a. (45/25,000)*100=0.18% (2)
b) Heat. (1)
c) Shorter food chains more efficient as there are less energy losses. Heron only gets 2 out of the 25,000kJ of energy absorbed. (2) Improvement?
d) Microorganisms consume the dead animals and plants causing decay. They then used the biomass for respiration which released carbon dioxide into the atmosphere - replacing CO2. CO2 then used in photosynthesis to be returned to the food chain. (3) Improvement?
a. Water moves through the partially permeable membrane by osmosis from the dilute solution to the more concentrated sugar solution causing the solution level to rise. (3) Improvement?
b) Would still increase, but at a slower rate the solution is less concentrated so smaller concentration gradient. (1) Improvement?
i. Gene. (1)
ii. Ribosomes. (1)
b) A combination of three bases codes for different amino acids. Amino acids then join together to create the protein which codes for blue eyes. (3) Improvement?
c) Different amino acids in structure. (1) Not sure...
ii) Different coloured eyes. (1) Not sure...
Adult bone marrow - Advantages
Does not kill embryos (1)
It is a simple operation (1)
Can still cure heart and blood diseases (1)
Adult bone marrow - Disadvantages
Embryonic stem cells - Advantages
Is not painful to patient (1)
Can develop into any type of cell so can cure more diseases (1)
Embryonic stem cells - Disadvantages