Edexcel igcse biology may 2012 exam discussion

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Reply 560

goxy

jogon mate at least i know what a zygote is

Reply 561

Umackjiggles

Original post by goxy

umackjiggles could u answer my question please?? :smile:

what was your question?

Reply 562

Big-Daddy

Original post by Umackjiggles

you would use it on explants that take it up and then you would grow them in a culture medium as per micropropagation. Not sure what this tumour you mention is.

OK, I see, don't worry about it ... I take it that if you don't know about it, we don't need it. :smile:

On the topic of GM plants, what would you say are the advantages versus disadvantages of modifying GM plants? It's directly stated on the specification, so I'm thinking, if GM's going to come up tomorrow, we should have some on hand.

beer production?

Original post by Big-Daddy

OK, I see, don't worry about it ... I take it that if you don't know about it, we don't need it. :smile:

I'm honoured :smile:

. Advantages are that you can grow a large collection of plants with advantageous phenotypes such as bacteria-resistance, temperature neutrality, etc. Disadvantages are that if the plants are insect-pollinated or indeed wind-pollinated their pollen might be distributed into the wild which would lead to heightened competition for nutrients and the subsequent death of plants and other organisms in the ecosystem (disruption of food chain) on account of the GM plants extraordinary ability to survive in abnormal conditions.

Reply 565

goxy

Original post by Umackjiggles

what was your question?

please could someone explain production of beer so that its understandable ??

Reply 566

Big-Daddy

Original post by Tentinator

A comprehension on the CNS

Learn to spell cord, not chord

This was posted from The Student Room's iPhone/iPad App

Yes, there are obviously going to be 3 different comprehensions, one on the topic covered in a comprehension in the same paper last year and one on a topic that's covered in the textbooks in about 3 lines. :rolleyes:

Reply 567

Tentinator

They asked about beer so they won't ask it tomorrow.

This was posted from The Student Room's iPhone/iPad App

Reply 568

goxy

please could someone explain production of beer so that its understandable ??

Reply 569

goxy

please could someone explain production of beer so that its understandable ?

Reply 570

Umackjiggles

Original post by goxy

please could someone explain production of beer so that its understandable ??

Ok I will break it down into 8 steps.

1. You germinate barley seeds on account of the fact that they produce the enzyme amylase (starch -> maltose -> glucose).
2. You kill the seeds by depriving them of heat and removing their food stores /crushing them and you dry them in order to make malt.
3. Ground up seeds and add to water.
4. Boil and filter solution.
5. Add hops for taste.
6. Add yeast (fungus) that respires aerobically until it runs out at which point it begins to respire anaerobically using the maltose/glucose in the fermenter.
7. Ethanol is produced as per C6H12O6 --> C2H5OH + CO2 (Not balanced).
8. Yeast dies once ethanol concentration goes above 15% at which point the solution is extracted and centrifuged/filtered before it is put in kegs and sold as beer.