Edexcel Biology IGCSE 2B Unofficial Mark Scheme 10th June 2016

yea, there were 0 homozygous dominant

I put fovea not retina! Will I get the mark d'you reckon?

but surely the amount of food to be digested will affect the time?

sameee- but i thinkn fovea will be one of the accept answers
cos rod cells and cone cells detect light and they are the most abundant in the fovea

Thank god, someone else! Ah good, thanks

the black sheet felt more like a physics question......
the majority of answers in my grade talked about: -retains heat /black absorbs heat/ reduces heat loss. -prevents water from evaporating and mineral ions from evaporating. And some rarer ones like prevents loss of nitrogent/nitrates from denitrifying bacteria or prevents other plants from growing (and competition for food) as it blocks sunlight. Not sure about the last two though

Does anyone know the answer to the question abut cholesterol building up in the arteries leading to the leg muscles?

haha good thats what i thought when i saw ur comment

I was really confused on this one, I thought of the physics stuff but I didn't think it could be right so I made something up. Oops.

i only managed to write in one point for that question. i ended up saying that black was a good absorber of heat therefore allowing sufficient light inside making it optimum for photosynthesis and respiration. but yeah awfully reminded me of physics

Cholestrol build up causes narrowing of artery - angina.
Therefore less blood travels through the artery per second.
Therefore less red blood cells.
Therefore less oxygen.
Muscles need oxygen for aerobic respiration
to provide energy for muscle cells.
Therefore muscles get extra energy required from anaerobic respiration
Glucose ---- lactic acid + energy
Lactic acid causes pains/cramps in leg muscles.
Lactic acid lowers pH, not optimum pH for enzymes, causing enzymes ot denature, active site no longer fits, causing some muscle cells to die.

You are right as well as me, I thought there was something wrong with it. Other people said it was 73.2 but it was 72.3 so it was 28.92 hence 28.9. Thanks.

Question 1 was what process do plants use to release glucose
Surely that's photosynthesis as that produces glucose whereas respiration uses it

Question 1 was what process do plants use to release glucose
Surely that's photosynthesis as that produces glucose whereas respiration uses it

i only managed to write in one point for that question. i ended up saying that black was a good absorber of heat therefore allowing sufficient light inside making it optimum for photosynthesis and respiration. but yeah awfully reminded me of physics

I put the enzyme as amylase

Thanks for replying. Thats more or less what I wrote but I wasn't exactly sure.

What will the grade boundaries for igcse biology be?

What do we think the grade boundary will be for an A*?